Full Paper(1) Centre for Marine Science & Technology, Curtin University
ABSTRACT
The Australian marine soundscape exhibits a diversity of sounds, which can be grouped into biophony, geophony and anthrophony based on their sources. Animals from tiny shrimp, to lobsters, fish and seals, to the largest animals on Earth, blue whales, contribute to the Australian marine biophony. Wind, rain, surf, Antarctic ice break-up and marine earthquakes make up the geophony. Ship traffic, mineral and petroleum exploration and production, construction, defence exercises and commercial fishing add to the anthrophony. While underwater recorders have become affordable mainstream equipment, precise sound recording and analysis remain an art. Australia's Integrated Marine Observing System (IMOS) consists of a network of oceanographic and remote sensors, including passive acoustic listening stations managed by the Centre for Marine Science & Technology, Curtin University, Perth. All of the acoustic recordings are freely available online. Long-term records up to a decade exist at some sites. The recordings provide an exciting window into the underwater world. We present examples of soundscapes from around Australia and discuss various aspects of soundscape recording, analysis and reporting—the to-dos and not-to-dos.
Aalto University
ABSTRACT
Concert hall acoustics is a multidisciplinary research topic, although often people think that it is only measuring and analysing impulse responses. This paper goes beyond the room impulse responses and explains in particular the features of sound sources and listeners in a concert hall. In addition, the paper collects the recent research results on subjective evaluations and discusses how halls affect the music and the impressions that live listening produces to listeners. The aim of the paper is to explain why the acoustics of a concert hall are hard to design with conventional methods and what are the issues that would need more attention in future research.
CH2M
ABSTRACT
In the 1980's, research in the United States led by NASA and NREL focused on the experience of those living near the first megawatt scale turbines. Starting in 2005, a biannual conference focusing solely on Wind Turbine Noise was established by I-INCE and wind turbine specific sessions are increasingly common at acoustical conferences. Recently, several large studies investigated individual and community response to wind developments. Most notably, Health Canada concluded its multi-year epidemiological study and similarly extensive efforts funded by Japanese Ministry of Environment have been published. The Crichton et al team from New Zealand published numerous papers on the role of the nocebo effect and infrasound and a small study in the UK measured the psychophysiological response to the visual impact of turbines on the landscape. In Australia, the Senate's "Select Committee on Wind Turbines" published a 350 page final report and disbanded, Australia's (and likely the worlds) first national Wind Farm Commissioner was appointed in late 2015 and the National Health and Medical Research Council's targeted grant for Research into Wind Farms and Human Health was recently awarded. This paper will summarize the highlights of the past, present and future research.
Air Noise Environment
ABSTRACT
Acoustic and noise have been important issues throughout the history of mankind. In the modern world, noise nuisance remains the most significant source of environmental complaints. This paper examines a range of environmental nuisance data from medieval times through to modern day records. Based on these data sources, the significance of noise complaints as a subset of environmental nuisance over the last 700 years is identified. Possible reasons for the current prevalence of noise nuisance in developed societies are explored in the context of historic and current issues, environmental regulation and planning approaches intended to prevent environmental nuisance arising, and in the context of new technologies and the potential for change in the future.
ABSTRACT
A number of recent projects involving audiences and critical listening have been designed based on a "perceptually efficient" concept. An outline of this evidence-based design strategy will be given together with a discussion of outcomes and insights from the completed projects.
Arup, Brisbane
ABSTRACT
The QUT Creative Industries Precinct Phase 2 (CIP2) co-locates the music, dance, performance and visual arts portfolios of the Creative Industries Faculty in a mixture of new-build and adaptive re-use of heritage structures. The acoustic design of CIP2 was of primary importance to the overall building performance and posed significant design challenges. The room acoustic design of CIP2 included design of two professional-quality recording studios, a large rehearsal/performance room, three interdisciplinary "black box" studios and several small rehearsal/practice rooms. The recording studios were designed to Dolby 5.1 standards, which involved challenges in fitting the required number of functional spaces into the available building area while maintaining the early-reflection control requirements of the Dolby guidelines. Ray-tracing design tools were used to develop the studio layouts taking into account the constraints of symmetry, favourable room ratios and the early-reflection requirements of the Dolby guidelines. Some studio spaces were façade-located which added challenges in controlling reflections and façade noise break-in. Additional flexibility in use was achieved by including variable-acoustics within studio live rooms via hinged panels.
(1) Akustikbuero Oldenburg (2) BARRISOL
ABSTRACT
Optically transparent sound absorbers made out of micro-perforated structures have been introduced 20 years ago. In between various applications and developments have been carried out. In this paper lighting sound absorbers or sound absorbing dayligth ceilings as well as fully transparent absorbers in front of gass facades will be shon. Sound absorption data for different set-ups are presented as well.
(1) Marshall Day Acoustics
ABSTRACT
Our approach to specifying industrial noise control and the assessment of environmental noise emissions from milk processing facilities has been developed over recent years while working on a large number of sites around New Zealand. This paper uses the Fonterra Darfield site, situated in Canterbury, New Zealand, as a case study to outline our current approach for rural green-field projects. Our involvement has included all stages of the project from early feasibility assessments, the consenting, design and commissioning of two stages of development, through to advising on future expansion plans. Our advice for the Darfield site addressed issues including environmental noise effects, setting contract specifications and protecting against potential reverse sensitivity effects. We have used three-dimensional computer noise models to inform our advice throughout the various stages of the project. This paper also discusses some of the key benefits and outcomes of this approach for both the client and project team.
(1) Arup, Melbourne (2) Arup, Brisbane
ABSTRACT
Recent projects at two Australian airports and one UK airport have highlighted some of the benefits and challenges in the use of auralisation as a tool for communicating the expected noise impacts from airport expansion projects. Opportunities for future development are also presented, including the use of signal processing to simulate changes to flight paths, changed meteorological conditions, or the changed noise emission characteristics of potential future aircraft. These projects also provide a useful body of data to investigate the application of the predicted noise levels from AS2021 in practice. The measurements suggest that AS2021 is broadly accurate in predicting noise levels from operation of Australian airports under typical flight conditions, but also highlight operational practices which may significantly increase the actual noise levels compared to the predicted noise levels based on idealised flight profiles.
ABSTRACT
The acoustic design of noise control treatments for industrial buildings should consider the costs of materials and construction as key design parameters. However, reducing the cost of the acoustic design is often given a lower priority than is given to the primary design requirement of achieving the noise level goals. An effective method to reduce the overall costs of the noise control treatments for an industrial building is to use engineering optimisation techniques. The selection of noise treatments can be undertaken by a computer based on the constraint that the noise control goals must be met, but with the deliberate intention to minimise the overall noise control cost. An engineering optimisation technique suitable for this application is the Genetic Algorithm. This paper demonstrates a method of using Genetic Algorithms to minimise the cost of noise control treatments for an industrial building with a variety of available wall and roof cladding materials.
ABSTRACT
The proliferation of highly conditioned or incomplete test data within manufacturer and supplier technical data sets creates substantial risk for all members of the acoustic community. This paper examines some of areas of concern to assist with mitigating the risks to acoustic professionals.
ABSTRACT
This paper gives an overview of the experiences gained in 35 years whilst working as a professional acoustics engineer in New Zealand and Australia with projects from Australia to the Middle East. Noise as unwanted sound is a subjective issue that varies significantly from building to building and country to country. Hence the controls applied in one building are not necessarily applicable to other buildings. Codes and standards only go part way to resolving this dilemma. Coupled with this are changes in instrumentation, testing methods and building materials. We are dealing with an industry that is changing with the professionals working with greater responsibility to adapt and change with the times. Codes and Standards are being challenged to more accurately reflect a variety of community expectations which means that there are needs for review processes, for regulations to be more flexible, and for more building acoustics research to be commissioned.
(1) School of Architecture and Design, Victoria University of Wellington, Wellington, New Zealand (2) Marshall Day Acoustics Limited, Wellington, New Zealand
ABSTRACT
This paper investigates how acoustic principles can be implemented within the architectural early design phase. The project work presented tested one parametric tool, Pachyderm, in a proof of concept, design of a café. Acoustic measurements were undertaken in six cafes and 30 café patrons completed a qualitative survey. In all cases measured ambient levels within the cafes exceeded the 50dBA LAeq criterion level suggested in the AS/NZS 2107 (2000). IRIS plots for each space showed a preponderance of late energy reflections (above 50 ms in most cases, with returns above 100 ms). Survey results suggested that the patron's ability to communicate decreased linearly as the café volume increased. In contrast, the patron's enjoyment of the café increased to a maximum then decreased quadratically as the volume increased. These qualitative and quantitative results formed acoustic design criteria that were implement into the design through a combination of Grasshopper and Pachyderm software.
(1) Department of Environment and Agriculture, Curtin University, Western Australia (2) Centre for Marine Science and Technology, Curtin University, Western Australia
ABSTRACT
The Perth Canyon, off the coast of Western Australia, is a hotspot for biological activity, high biomass and biodiversity. It is also an area that is still relatively understudied. In this study, combinations of passive and active acoustical methodologies were used to study biological activity in the Canyon; and in particular, diel vertical migration. Data from sea noise loggers and Acoustical Doppler Current Profilers (ADCPs) mounted along the Perth Canyon were collected as part of the Integrated Marine Observing System (IMOS) program. The sea noise data recorded post-sunset fish choruses and the backscatter logged by the ADCP deployments measured increased scattering in the upper layers of the waters between sunset and sunrise. These two types of data provide an insight into secondary productivity in the Perth Canyon. This study revealed a correlation between the fish chorus noise level and the increase in scattering in the water column. Future research is planned to determine the sources and the reason(s) for the temporal variation of these phenomena.
(1) The University of Queensland
ABSTRACT
Sound travels with greater efficiency in water than does light, which is quickly absorbed and scattered. As a consequence, a wide variety of marine taxa use sound for communication, foraging and generally sensing their environment. Since the 1970s there has been increasing concern about the potential impacts of underwater anthropogenic noise on marine animals. Sources range from short-term coastal ones such as pile driving, to those which contribute long-term, sustained increases in ambient noise, such as shipping. Cetaceans (whales, dolphins and porpoises) are a group of marine animals thought to be at particular risk to impacts from anthropogenic noise. One type of study that has been used to determine the short-term impacts of noise on various taxa is the Behavioural Response Study (BRS) where animals are exposed to a noise and their behavioural responses are measured. While BRS are relatively straightforward for captive animals, most species of cetaceans are not kept in captivity and experiments with adequate levels of control are difficult. One such study, however, is the Behavioural Response of Australian Humpback whales to Seismic Surveys (BRAHSS), which commenced in 2010. Migrating humpback whales were exposed to high level, impulsive sounds from arrays of seismic airguns off the Sunshine Coast, north of Brisbane, and off Dongara in Western Australia. The airguns, from a single 20 in3 airgun to an array of 3130 in3, were towed behind a source vessel while whales were tracked and their behaviours observed from small boats and land stations. The success of the project required the accurate estimation of the received levels of the source vessel noise and airgun noise, as well as careful measurement and interpretation of behavioural data. This large study is an example of the need for careful study design and collaboration between experts in several fields including underwater acoustics and animal behaviour.
(1) AECOM
ABSTRACT
In 2014 the Australian Rail Track Corporation (ARTC) completed the Scone Reconfiguration Project. The reconfiguration project included the removal and realignment of existing rail infrastructure and the construction and installation of new turnouts. The reconfiguration allows trains to travel through the Scone township at an operational speed of 50 km/h rather than 25 km/h. The increased operational speed increased wayside noise levels, resulting in the recommendation of reasonable and feasible noise mitigation. A combination of noise barriers and architectural treatment was recommended. One noise barrier, 4.2 metres high, extends partially across the north side of St Aubins Street West (on the Down side of the tracks). A warehouse is located on the Up side of the St Aubins Street, resulting in a gap in the noise wall of approximately 17 metres. The resulting noise environment comprises noise from trains that are well shielded and then suddenly emerge from the noise barrier creating a fast and appreciable onset of noise. The majority of movements are freight at this location. While the rail line has existed at this location as long as the township, long-time residents have begun complaining as a result of the new noise wall. It has been claimed that the new noise wall has created an annoyance issue. The exhaust noise is the dominant noise source contributing to the reported annoyance. This paper explores the local noise environment, establishes a means to determine annoyance which relates to existing noise criteria and considers other psychological factors which can contribute to the annoyance associated with the environment. Findings are provided which include recommendations for determining the likelihood of annoyance as a result of the onset of noise and recommendations to mitigate against the occurrence of these events.
(1) WSP | Parsons Brinckerhoff
ABSTRACT
In this paper, some of the well-known rail prediction methodologies, such as Kilde Rep 130, Nord2000 and the United States' FTA (Federal Transit Administration) methodologies are compared using a simple elevated rail model. An overview of the relevance and applicability of these source models for an elevated rail design is provided. For each of the above mentioned methodologies, simple single point receiver results for an at-grade and an elevated rail design are presented. Further, a test-case representing a real-world scenario is also studied using these different methodologies. The results indicate a significant variation in predicted noise levels across the methodologies. Kilde Rep 130 is found to be conservative, and predicts minimum shielding from the bridge structure. On the other hand, Nord2000 implements source directivity, thereby predicting larger shielding effects from the base bridge and barrier structures. FTA methodology provides a flexibility to use a more simplistic ISO 9613 propagation model, which reduces computational time. While the accuracy of these methodologies can be only determined by comprehensive field measurements, the paper provides an insight into the effectiveness of these methodologies when carrying out predictive modelling of rail operational noise for an elevated rail design.
The University of Queensland
ABSTRACT
Railway technology continues to provide challenges in the dynamical and acoustical analysis of engineering systems that typically behave in nonlinear regimes. This seminar will outline some of the new (and old!) research being undertaken in this area by the Rail Mechanics Group at The University of Queensland, Australia. In particular, results for prediction, control and measurement of rail corrugation, locomotive traction dynamical phenomena and prediction and field investigation of wheel squeal and railway noise will be presented. The paper will particularly focus on the prediction of vibration amplitude and sound pressure level of wheel squeal noise using a concise mathematical model which has been validated with results from a rolling contact two disk test rig. In particular, a closed form solution to the steady state limit cycle amplitude of creep and vibration oscillations during squealing are obtained. The predicted squeal sound level trend is then shown to compare well with that recorded at various crabbing velocities for the test rig at different rolling speeds. The results concur with experimental and field observations but also provide important theoretical insight into the useful mechanisms of controlling wheel squeal noise and quantifying their relative merits.
ABSTRACT
The concept of Fresnel Zones arises from considering reflection paths off a surface differing from the direct sound propagation path by some multiple of half a wavelength. The modelling of these zones, and of zones derived using a set time delay, provides useful insights for the design of spaces for listening and communication. This paper gives an overview of analysis using this approach together with some examples. Exact and approximate formulae are discussed.
(1) School of Engineering and ICT, University of Tasmania, Hobart, Australia
ABSTRACT
Acoustic diffusers are designed to scatter sound to create diffuse sound fields, ideally providing a uniform acoustic experience over a broad frequency range within a listening space. Standard diffuser designs, such as Schroeder diffusers, while effective, may be considered by some to have a design aesthetic that does not conform to particular architectural styles. In this paper the Fourier Synthesis algorithm for procedural 3D random terrain generation is investigated as an alternative for diffuser surface geometry, providing scattering in two dimensions, and scope to vary the bandwidth through a surface smoothness parameter. The scattering properties of a prototype diffuser are investigated experimentally and through numerical modelling using a boundary element method (BEM) program called FastBEM. Good agreement between these is achieved, providing solid validation of the numerical model from which the performance of the diffuser can be assessed. The scattering properties are quantified using polar plots, 3D plots, and the diffusion coefficient. As expected, the Fourier Synthesis diffuser provides good diffusion when the wavelength of the incident sound is comparable to the wavelength of periodicity of the diffuser geometry. A preliminary investigation into the performance of the diffuser for various levels of surface roughness is made, showing that high diffusion can be extended to higher frequencies by increasing the surface roughness of the diffuser.
Marshall Day Acoustics
ABSTRACT
The use of suspended baffles to provide acoustic absorption is an increasingly common option where the building design requires the underside of a slab to remain exposed. Test data for sound absorption is provided by some suppliers for specific configurations of baffles i.e. depth of baffle, spacing between baffles, and hang distance from the slab. However, often the demands of a project require baffle arrangements that have not been tested. This presentation explores the possibility of using the Odeon room acoustics modelling software to calculate the absorption coefficients of different baffle configurations without relying on physical laboratory tests. By using a virtual reverberation chamber, the laboratory test procedure from ISO 354: 2003 has been replicated in Odeon. The predicted absorption coefficients have been compared to data from suppliers' tests in an attempt to validate the modelling process.
(1) School of Mechanical Engineering, The University of Adelaide, SA 5005, Australia (2) Department of Chemistry, The University of Adelaide, SA 5005, Australia (3) Department of Biomedical, Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, OH 45221, USA
ABSTRACT
Previous investigations have shown that a 3-mm-high carbon nanotube (CNT) forest has an acoustic absorption coefficient of about 5-10% within the frequency range 125 Hz-4 kHz, which is above that of conventional acoustic materials on a per-mass basis. It was hypothesised that a CNT array of greater height, lower density, and with a non-uniform arrangement of the nanotubes could enhance the amount of acoustic absorption. In order to investigate this hypothesis, an impedance tube test was conducted to measure the acoustic absorption coefficient of a relatively tall 6-mm CNT forest. The results indicate that a greater length and lower density of CNTs may improve the absorption performance of CNT-based acoustic absorbers. Analyses of the results showed anomalies in the measured acoustic absorption coefficient compared with previous investigations. Theoretical analyses were performed based on classical models of acoustic absorption to explain the anomalies. This study describes the factors that may affect the acoustic absorption behaviour of nanomaterials.
(1) The University of Auckland (2) International Islamic University Malaysia
ABSTRACT
This paper presents a method of calculating the radiated sound power of vibrating structures based on the time domain estimation of acoustic radiation modes (ARMs). Each ARM is frequency-dependent, radiates power independent of the other ARMs and can be estimated in the time domain from measurements made at discrete sensor locations on the surface of the radiating structure. The individual ARM components are estimated digitally in the time domain using finite impulse response filters, which are designed to provide a best weighted fit to the ARMs in the frequency domain. The ARM amplitudes are estimated by filtering the vectors of measured velocities at points on the radiating surface with these ARM filters, before summing the product of the square of these amplitudes with the relevant eigenvalues to estimate the radiated sound power. The method is described with reference to a simply supported beam model. The results show that the sound power calculated from the proposed approach and from a frequency domain approach are comparable. Finally, a time domain feedforward active structural acoustic control system developed using the proposed method is presented and time domain simulations demonstrate the performance of the system.
(1) University of Technology Sydney (2) Nanjing University
ABSTRACT
A virtual sound barrier is an active noise control system that uses arrays of loudspeakers and microphones to create a practical size of quiet zone in a noise environment just like an acoustic barrier but without blocking air and light. This technology can be used to reduce sound radiation from noise sources or to reduce noise level around one or few person heads in noisy environments in many industrial and domestic situations. This paper introduces the history, principle and design methods of the virtual sound barriers first, and then describes recent progress in research on the systems, especially the application on power transformer noise radiation control from an enclosure. The paper is concluded by the limitations and future direction discussions of the virtual sound barriers.
(1) University of Sydney
ABSTRACT
A set of sounds were recorded with the intension of sounding unpleasant. The sounds comprised of 6 stimuli that can be described as grinding, screeching and scraping. Reported unpleasantness of the sounds were manipulated via task variables such as the presence or absence of task instruction text related to the potential unpleasantness of the presented sounds. A good example of the influence of such ideational factors on the reported unpleasantness of recorded sounds is the inclusion of a description of fingernails scraping across a blackboard when presenting the sound of a sharp object scraping across a slate surface. The sounds were also manipulated through spectral processing and presented to listeners in full broadband spectrum, as a high pass filtered version above 500Hz and low pass version below 500Hz. These three versions were presented with and without ideational descriptors and rated on a 10-point scale by listeners. Median values of rated unpleasantness suggest that the frequency content above 500Hz is most contributing to unpleasantness, and that ideational factors have greater effect when describing sounds in this frequency spectrum.
Broner Consulting Pty Ltd
ABSTRACT
In acoustics, we often are required to demonstrate compliance with a given criterion. The criteria may be specified in a regulation or a specification. When acoustic measurements are conducted to demonstrate compliance, there needs to be a consideration of the uncertainties of measurement and there needs to be an understanding of what the criterion is requiring as well as an understanding of what you are measuring. For example, when measuring environmental noise to check compliance with an EPA criterion, is the case that the actual criterion never be exceeded or can it be exceeded by some amount for say 50% of the time. And if you measure a noise level of 50.1 dBA when the criterion is 50 dBA, is this really a fail or is it a pass? In this paper, some of these complexities will be explored.
AECOM
ABSTRACT
Poorly implemented or unsatisfactory acoustic design can be very difficult and expensive to remedy. Accordingly, acoustic treatments are typically most cost effective when they form the part of an integrated design solution rather than applied as remedial fixes. This paper firstly presents a discussion of the basic information that should be considered in scoping or briefing projects. Secondly, the designer's obligation to ensure treatments and associated performance metrics are clearly articulated and understood is explored with emphasis on the importance of co-ordination for an integrated design. Here the question is posed, how does one effectively communicate expected outcomes, quality and risk to designers and stakeholders? Particularly given that such information is of critical importance in empowering clients to make decisions around risk and cost. In addition, suggestions and guidance are provided relating to other factors that influence the successful delivery of a project. Finally, this paper seeks to share this knowledge with the aim to improve the consistency and quality of acoustic advice provided within the consulting industry.
MAAS
ABSTRACT
The Building Code of Australia [BCA] presents a one-size-fits-all approach to the provision of adequate acoustic amenity for new construction. To quote from the document, "The BCA is a uniform set of technical provisions for the design and construction of buildings and other structures". Acousticians must constantly interpret the provisions and perhaps the intent, of the Code for our clients; often in conflict with margin-poor constructors doing "it" the way they have always done. The BCA is given legal effect by building regulatory legislation in each State and Territory and while the various pieces of legislation differ, they all give the BCA the force of law. In our increasingly risk adverse construction environment there is a need to adhere more carefully to due process as we provide our recommendations and expert opinions. This paper gives an acoustician's understanding of the process whereby the Code provisions are presented and the process by which acoustic "certification" should be documented. Further, it presents a path by which variations to Code deemed-to-satisfy provisions ("performance solutions") can be introduced in a manner such as to limit unintended consequences and allow others to "tick-the-boxes" on the path to certification.
(1) JASCO Applied Sciences Australia (2) JASCO Applied Sciences Canada
ABSTRACT
The soundscape in Australian waters demonstrates a high level of variability, and is dependent upon the relative contributions from geophonic, biophonic and anthrophonic contributors. There is increasing interest in understanding soundscapes due to the implications for assessment of anthropogenic activities. Significant information exists in acoustic recordings, with a number of methods used to characterise contributors. This paper describes a new technique, the Acoustic Variability Index, that appears to be useful in distinguishing periods of transient sounds from continuous sound sources. Acoustic recordings from 30 long-term monitoring recordings from 10 geographic regions around Australia have been analysed using typical characterisation techniques and the Acoustic Variability Index. The Acoustic Variability Index results are compared with those from typical automated characterisation techniques applied to large datasets, and its value to determine changes in the soundscape is discussed. Increased understanding of the marine soundscape and its contributors is important to assist informed spatial planning of reserves and both spatial and temporal planning for anthropogenic activities.
(1) Curtin University
ABSTRACT
Effective management of demersal fish species includes accurate, spatially explicit assessments of their abundance and distribution. Non-extractive techniques, such as echo-sounders and visual census, are of particular importance in no-take marine reserves where direct sampling is restricted. This study is investigating the use of echo-sounders and Baited Remote Underwater stereo-Videos (stereo-BRUVs) in demersal fish assessment. Echo-sounders have the advantage of covering nearly the entire watercolumn and being able to cover vast areas in a relatively short period. However, "ground-truth" data is usually needed to produce species-specific identification and sampling the area close to the seafloor is problematic, particularly for demersal species in complex topography. In contrast, stereo-BRUVs allow identification to species level in most cases, but samples characterise a particular location within the field of view and the area of influence within the bait plume. The combination of co-located bathymetric and habitat maps, with quantifiable acoustic backscatter and species-specific visually ground-truthed relative abundance, holds potential to further these studies and provide a more cost- and labour-efficient sampling regime. The preliminary investigation into the relationship between active acoustic and stereo-BRUVs showed a significant correlation between the relative biomass recorded by the stereo-BRUVs and the acoustic energy recorded by the echosounder.
(1) CMST, Curtin University (2) DSTG and School of Geosciences, University of Sydney
ABSTRACT
Measurements of the transmission of seismic survey signals in Australian waters are presented. The measured transmission loss showed: high variability of received signal sound exposure level at similar ranges when comparing all surveys (mean of standard deviation across ranges of 3-12 dB); high variability within a seismic survey (mean of standard deviation at any range of 2-4 dB); typical shot-shot variability of 1-3 dB (mean of standard deviation at any range) possibly produced by gun strings moving around; the importance of bathymetry profiles, seabed types and sound speed profiles in determining air gun transmission; different transmission regimes for open ocean, continental shelf and shelf-slope environments; seismic source energy transmitted at longer ranges (> 1 km) was most commonly dominated by low frequency (< 500 Hz) energy and only at short range (< 1 km) was high frequency energy observed; and that a considerable amount of air gun array energy may directly excite the seabed, couple into the seabed and travel horizontally, or by way of interface waves. For locations on the shelf or shelf slope around southern and western Australia the presence of limestone or calcarenite seabed types are critical in accurately determining seismic signal transmission.
(1) Curtin University (2) CSIRO
ABSTRACT
Investigating the pelagic community of the Great Australian Bight (GAB) remotely and pervasively remains an elusive challenge to the scientific community. Advanced broadband acoustic sounders offer a new tool to help characterise and subsequently classify the dominant scatterers via the frequency dependence of their target strengths. Broadband acoustic data were collected from the GAB for the first time on a recent scientific expedition on board RV Investigator in December 2015. A broadband sonar system (EK80), mounted on a custom designed vertical profiling acoustic platform was used to record acoustic data in the frequency range of 45 - 160 kHz. A processing method was developed to allow the system to be calibrated at depth with a reference target so that the frequency dependence of scattering from biological targets could be measured independently of their positions in the acoustic beam. The results of some initial tests of the method are reported here and include the measurement of the frequency dependent target strength of two targets at a depth of 600 m. The characteristics of these frequency response curves indicated that one was an animal with a gas inclusion whereas the other behaved like a fluid scatterer. No independent ground truthing was available to confirm this; however, these results indicate that the broadband acoustic method has considerable promise as a new tool to study the pelagic community of the region. This study is being undertaken as part of the Great Australian Bight Research Program, a collaboration between BP, CSIRO, the South Australian Research and Development Institute (SARDI), the University of Adelaide, and Flinders University. The Program aims to provide a whole-of-system understanding of the environment, economic and social values of the region; providing an information source for all to use.
(1) Director, Acoustics RB Pty Ltd (2) Senior Engineering Technician, Acoustics RB Pty Ltd
ABSTRACT
QDC MP 4.4 Buildings in a Transport Noise Corridor was gazetted by the Queensland State Government on 1 September 2010. The stated purpose of QDC MP 4.4 is to ensure habitable rooms of Class 1, 2, 3 and 4 buildings (ie residential dwellings) located in a Transport Noise Corridor are designed and constructed to reduce transport noise. The extent of building upgrade may be determined by reference to deemed-to-comply building constructions or the results of a site-specific acoustical design review. For sites adjacent to major roads, the deemed-to-comply building constructions and the building upgrade performance requirements set by the Code tend to overstate the degree of attenuation required. For sites adjacent to rail lines that are trafficked by electric passenger trains only, the deemed-to-comply building upgrade performance requirements are generally quite comparable to the actual upgrades required when these are determined using the site-specific method. By contrast, it has been found that, in situations where residences to be constructed on sites adjacent to rail lines trafficked by diesel trains as well, the deemed-to-comply building upgrade performance requirements are often not sufficient to adequately control rail noise intrusion. This paper attempts to quantify the degree to which the building upgrade performance requirements fall short of the mark as well as provide guidance on methods of addressing this shortfall.
ABSTRACT
There are many standards and guidelines that can be used to assist in expressing measurement uncertainty, however there aren't many that can assist in determining uncertainties in noise predictions and design risks. A common way that noise and vibration engineers deal with prediction uncertainties is to assume an uncertainty of +/- X dB in their modelling or to simply add a safety factor of +Y dB to their design. This paper shows how international guidelines were used on some recent rail transport infrastructure projects to quantify the uncertainties in noise predictions and to establish the level of design risk associated with those uncertainties. Prediction uncertainties were determined from the methodologies described in the International Standard ISO/IEC Guide 98-3 'Guide to the expression of uncertainty in measurement' (GUM) and by establishing an uncertainty budget for each part of the ground-borne noise and prediction process (source, path and receiver). A Monte Carlo simulation was also undertaken with 100,000 iterations to provide an estimate of the standard uncertainty. This was compared with the GUM approach and gave similar results.
(1) University of Queensland
ABSTRACT
The replacement of axle bearings in trains is a very involved process and costs operators in the order of millions of dollars per maintenance cycle of a fleet. At present, maintenance scheduling is performed at predetermined time intervals. Predicting the wear and degradation of the bearings, would enable operators and bearing manufacturers to 1) optimise the design and maintenance of the bearings, and 2) quantitatively determine the best time to replace the bearings. This paper presents a model developed for predicting the wear in radially loaded spherical roller railway axle bearings, using a slice method to calculate the roller load, traction and creep distribution along the roller for the contact mechanics, and predict wear using a frictional power model. The model includes a feedback process between the accumulation of wear, using particles in the grease, and the friction and wear rates in the bearing. The wear contribution from each roller in the loading zone due to the radial loading is calculated and combined for an overall wear profile for the inner and outer races. Initial validation was performed by comparison with thrust bearing results in the literature. Then the wear of used bearings of a known mileage was used to validate the fully developed model, giving good agreement between the simulation results and the used bearings. Several case studies were performed on the fully developed model, including 1) determining the effects of radial loading, where it was found that there is less wear for radial loading than for axial/thrust loading for the same maximum roller load, and 2) comparing the differences in wear between the inner and outer race, where it was found that the inner race wears more than the outer race due to the higher number of contact events per revolution, due to its smaller radius. To optimise the bearing life, a sensitivity analysis was performed on the effect of the wear and friction coefficients showing that both of these parameters have a significant effect on the wear volume over the duration of the simulation. An increase in the life of the bearing, based on the wear volume, was able to be made when controlling these parameters, as could be done with a grease maintenance strategy.
ABSTRACT
30 years in the planning and 8 years in the design and construction, the Philharmonie de Paris, Grande Salle opened in January 2015. The 40 page acoustic brief, prepared by Eckhard Kahle, was probably the most comprehensive acoustic brief ever written for a concert hall. The brief called for great clarity and high reverberance, considered by some to be mutually exclusive, and specified more than 10 acoustical parameters to be achieved in the room. The architectural brief also stated; 'The design must be a new typology: it could not be a shoebox, vineyard, fan or arena shaped hall.' The design team headed by French architect, Jean Nouvel and lead acoustician, Sir Harold Marshall, conceived the room during a synergetic design workshop with the architect, acoustician and theatre consultant working in a highly collaborative environment. The concept design for the Philharmonie aimed to balance early and late acoustic energy by nesting an intimate audience chamber within a larger acoustic volume. The complex geometry of the hall, with its inner and outer volumes with multiple curved surfaces, was beyond the capabilities of common acoustic simulation packages and processors. New technologies in 3D modelling and parametric design were developed along with an interactive approach, followed by the formal acoustic simulation in ODEON. The latter was subsequently validated by a physical scale model study. This paper presents the steps in the acoustic design process and the tools used to deliver a radical but successful design. Commissioning the Grand Salle of the Philharmonie de Paris was never going to be straight forward due to its multiple uses, encompassing classical symphonic, choral and recital repertoire, contemporary music, Jazz, and World Music. Add in highly adaptable stage and seating arrangements, and the mechanics of making these changes, and a protracted series of measurements both occupied and unoccupied, were inevitable. Complicating this task have been cost overruns, construction delays, politics and an extensive programme booked out months in advance. The measurements were made in a series of brief windows of availability, using the MDA-developed IRIS system. The Philharmonie opened on the 14 January 2015, after many weeks of 24 hours a day construction. The building however was incomplete and the architect refused to attend in protest. Reviews by musicians and the press are summarised in the paper.
(1) Arup, Brisbane (2) Arup, Melbourne
ABSTRACT
The recently-opened Ukaria Concert Hall (formerly Ngeringa Concert Hall) is an intimate chamber music recital space. The acoustic design of the hall faced the challenge of achieving good acoustics for chamber music within an overall-concave architectural room form, while providing comparable acoustic quality to historical European precedent venues. A key component of the room design was the shaping of the room surfaces to reduce focussing, provide high clarity and provide a strong sense of immersion as per a traditional rectangular hall. Key design features include the provision of additional lateral reflection paths above the audience area and a highly-diffusive reciprocal-frame ceiling. The design of sound scattering surfaces in the room was done using Boundary Element Modelling (BEM) to create room elements that were inherently part of the room aesthetic but also were functional acoustically. The resulting hall has high subjective reverberance, clarity and immersion despite its relatively-small size and seating capacity and has been acclaimed by both musicians and audiences.
Akustikbuero Oldenburg
ABSTRACT
DIN 18041 was revised from October 2013 to mid 2015, and published in early 2016 with the new title "Acoustic quality in rooms - requirements, recommendations and instructions for planning", The new edition of the standard includes a number of clarifications, additions and deletions and includes for the first time explicit guidance for room acoustics to address the particular needs of the hearing impaired. This paper presents a summary of the revised standard and reviews some of the considerations behind the various changes made.
(1) School of Mechanical Engineering, Queensland University of Technology, Brisbane, Australia
ABSTRACT
This paper focuses on the design of a pipe-pump system for use in conducting research on the topic of pipeline condition monitoring using acoustic emission sensors. Analysis of acoustic emission properties, pipe leak fluid dynamics and frequency caused by fluid dynamic events are discussed to support the design of the test-rig and inform the future analysis of the acoustic emission signals. Computational fluid dynamics is conducted on a simulated leak with varying parameters to ensure that the design was suitable in being able to test and verify this type of condition monitoring. Plans for future work with regards to conducting testing on this pipeline are also discussed to support verification of the use of acoustic emission sensors for detecting and locating pipeline leaks.
(1) UniSA
ABSTRACT
The acoustic signature of a propeller-driven unmanned aerial vehicle comprises a set of strong narrowband tones superimposed onto a broadband random component. When the aircraft overflies an array of microphones, by comparing projected and observed narrowband tones, propagation delays between source and receiver may be determined. These may then be converted into effective sound speed values and 2- and 3D spatially varying atmospheric temperature and wind velocity fields estimated using tomography. In this paper realistic conditions for a weakly sheared daytime convective atmospheric boundary layer are used to assess the anticipated performance envelope of the technique. The properties of the simulated atmosphere are synthesised through use of massively parallel large eddy simulation that utilises pseudo-spectral differencing in horizontal planes and solves an elliptic pressure equation. Particular attention is paid to the accuracy with which the surface layer (lowest 50m of the atmosphere) may be reconstructed as this region typically experiences the greatest spatio-temporal variation in temperature and wind speed.
(1) Mechanics of Materials and Structures MMS, Faculty of Engineering and Architecture, Ghent University, 9000 Gent, Belgium (2) Lumilab, Faculty of Sciences, Ghent University, 9000 Gent, Belgium
ABSTRACT
A material is called piezoluminescent when it emits cold-body radiation during mechanical stimulation in the elastic regime. Such materials are already used for non-destructive pressure sensing and for mapping personal hand writing. In this contribution, we focus on a recently developed luminescent phosphor BaSi2O2N2:Eu (BaSiON), and report on Acoustically induced PiezoLuminescence (APL). Insonification of the BaSiON phosphor (thin plate) with (ultra)sound waves leads to intense light emission patterns which are clearly visible by the bare eye. The emitted light intensity has been measured with a calibrated photometer, and it is found that the light emission is directly proportional to the applied acoustic power. Hence, the APL phenomenon can be used to construct an absolute pressure sensor for (ultra)sonic waves. Further, we observed that the emitted light pattern has a specific geometrical shape. We successfully linked this geometrical shape to the local spatial nature of the incident (ultra)sonic wave. This is explicitly demonstrated for a standard ultrasonic transducer (used for nondestructive testing and medical applications) which is operated in the MHz regime. By varying the insonification distance (from near field to far field), multiple 2D slices of the transducer's radiation field light up on the BaSiON phosphor plate. Simply photographing these light patterns, the full 3D spatial radiation field of the transducer was reconstructed in practically real-time. The APL reconstructed pressure field has been confronted with classical scanning hydrophone experiments as well as with ultrasonic holography, showing good correspondence. Although the current APL results were obtained for MHz frequencies, similar results have been obtained for acoustic frequencies in our laboratory. This clearly shows the great potential of the APL phenomenon for a range of applications in (ultra)sonics, as well as for real-time imaging of mechanical waves.
Pyrotek Noise Control
ABSTRACT
A reverberation room was desired on-site in order to measure the absorption coefficients of materials during the research and development process without utilising external laboratories. Making use of the available resources, a regular office was converted into a small-scale reverberation room. Whilst an ideal reverberation room has a volume of at least 200 m3, this reverberation room was designed around the limited 48 m3 room volume. Significant construction work was conducted to convert the room, including the implementation of diffusion panels. Verification of the room was carried out by testing in conformance with ISO 354:2003 (with deviation to account for the room volume) using Reapor®, which has been tested in four different full-scale reverberation rooms to the same ISO 354:2003 standard, allowing comparisons to be drawn. Testing revealed satisfactory correlation between the small-scale and full-scale reverberation rooms. A small-scale reverberation room was successfully developed, saving time and resources by enabling us to test the sound absorption coefficients of materials during the research and development process, before sending the final material to an independent acoustical laboratory for accredited ISO 354:2003 results.
(1) University of South Australia
ABSTRACT
Acoustic Atmospheric Tomography provides a unique way to measure temperature and wind velocity fields in a slice or volume of atmosphere. There are many applications for these measurements, including atmospheric research, weather forecasting, pollution studies, agricultural monitoring etc. The technique discussed in this paper makes use of an Unmanned Aerial Vehicle that is flown over an array of microphones on the ground. The natural sound emitted by the aircraft is recorded on-board and by the ground microphones. The speed of sound of the intersecting rays are then derived by comparing these measurements. Tomographic inversion is then used to estimate the temperature and wind fields from the sound speed measurements. This technique estimates continuous, three dimensional temperature and wind fields from ground level up to at least 1000 metres. Previous studies have indicated that the sound speed measurements must be accurate to within 0.1% in order to obtain useful results. This paper describes the signal processing techniques that have been employed on field trials data to provide estimates of the atmospheric temperature and wind fields pertaining at that time.
(1) School of Mechanical Engineering, University of Adelaide, Adelaide, South Australia, 5005, Australia (2) School of Mechanical and Manufacturing Engineering, UNSW, Sydney, NSW, 2052, Australia (3) ASC Pty Ltd, Osborne, South Australia, 5017, Australia
ABSTRACT
It is important to be able to accurately model the flow and noise generated by finite wall-mounted airfoils because of the many engineering applications in which these flows occur. One method for predicting turbulent trailing edge noise is the Reynolds averaged Navier-Stokes based statistical noise model (RSNM) (Doolan et al. 2010) which has been applied successfully to a range of two-dimensional geometry flow cases. For these 2D cases the spanwise extent was accounted for by means of a correction factor following the approach of Corcos (1964). However, such a correction is not suitable for application to more complex three-dimensional flow cases. Furthermore, to achieve accurate evaluation of the far-field power spectral density using such an implementation requires an acoustic cell discretisation such that each of the cells have extents smaller than the characteristic length scales ("l" _"s" ) of the turbulence within them. The fine spatial discretisation required to meet this criterion, especially for three-dimensional flow cases, can be prohibitively computationally intensive. These limitations drove the development of a new turbulent velocity cross-spectrum model which implicitly takes account of the spanwise extent, and also permits a coarser acoustic discretisation which drastically reduces the complexity of the resulting noise calculation. The developed turbulent velocity cross-spectrum model and improved implementation allow the RSNM method to be used to effectively and efficiently predict turbulent trailing edge noise from more complex three-dimensional cases. Reynolds-averaged Navier-Stokes (RANS) simulations of a series of finite wall-mounted airfoil flow cases were used in combination with the acoustic model to predict the far-field noise and compared against experimental noise measurements.
Department of Mechanical Engineering, University of Auckland, Auckland, New Zealand
ABSTRACT
A contra-rotating advanced open rotor is a novel aeronautical propulsor which promises significant reductions in fuel burn relative to current generation turbofan engines. It has been the subject of much research by the aeronautical industry over the past decade. This paper briefly summarises a number of experimental investigations which have been undertaken using model-scale rotors and describes some of the issues encountered during and findings from these tests. A description of a relatively straightforward 'frequency-domain' analytical method for predicting the tonal noise produced by these engines is also provided. The paper concludes with demonstration of how this analytical method can be used to assist in the design of a quiet contra-rotating open rotor engine.
Defence Science & Technology Group
ABSTRACT
Hostile small arms fire poses a serious threat to the military community. A capability to locate the sniper or point of fire is essential for an effective counter-sniper system. The firing of a supersonic bullet produces two acoustic impulses: the muzzle blast (MB) generated during the launch of the bullet from the rifle and the ballistic shock wave (SW) generated by the supersonic flight of the bullet. The point of fire can be located using the MB arrivals, the SW arrivals, or both at an array of acoustic sensors distributed around the target of the sniper or within the protected area. As the shooting range increases, the MB arrivals become too weak and only the SW arrivals can be used. This is because the amplitudes of the MB arrivals decrease with the shooting range while the amplitudes of the SW arrivals are (approximately) independent of the shooting range. One approach to sniper localization using SW arrivals is to first estimate the trajectory of the bullet, and then trace the trajectory back to (topographic or man-made) obstructions on a digital map. This paper considers the estimation of the trajectory of a supersonic bullet using the observed time delay between the SW arrivals at each sensor pair of an acoustic array. In practice, the bullet decelerates along its trajectory due to the drag force, and the decreasing speed of the bullet is accurately modelled as a quadratic function of the distance travelled. A mathematical formulation of the bullet trajectory estimation problem is presented, followed by a Cramer-Rao lower bound (CRLB) error analysis. A nonlinear least-squares (LS) solution to the bullet trajectory estimation problem is then described, which assumes that the ballistic constant of the bullet is known a priori or has been correctly estimated by some means. Any uncertainty in the ballistic constant will degrade the accuracy of the bullet trajectory estimation and subsequently the accuracy of the sniper localization. This degrading effect of an erroneous ballistic constant and the performance of the nonlinear LS method when the ballistic constant is exactly known are evaluated using both simulated data and real data recorded from a field experiment for two different types of bullets.
(1) School of Mechanical and Manufacturing Engineering, UNSW Australia, Sydney NSW 2052, Australia
ABSTRACT
This paper presents a computational analysis of the flow-induced noise generated by a sharp-edged symmetric flat-plate located in low Mach number flow using the hybrid computational fluid dynamics (CFD)-boundary element method (BEM) and the Time-Reversal (TR) source localisation techniques. The CFD-BEM method is used to obtain the far-field acoustic spectrum of (1) the direct field generated by the turbulent flow over the flat-plate, (2) the acoustic field scattered by the body and (3) the total acoustic field at all four computational boundaries. The far-field acoustic spectrum for all three cases exhibits a broadband nature whereby the time-domain acoustic pressure data is obtained using the inverse Fast Fourier Transform followed by band-passing the signals in 1/3rd octave bands. The aeroacoustic TR simulations were implemented by numerically solving a set of 2-D Linearised Euler Equations and enforcing the band-passed time-reversed acoustic pressure signals as input at the boundary nodes. The TR source maps corresponding to the direct field indicates a lateral quadrupole source located downstream of the Trailing-Edge (TE) in the low-frequency range and a dominant longitudinal quadrupole located at the Leading-Edge (LE) in the high-frequency range. For both scattered and total fields, the TR source maps indicate a lift-dipole source at the TE in the low-frequency range whilst in the high-frequency range, the source maps indicate the occurrence of a weaker dipole source at the LE and a dominant dipole source at the TE.
CMST, Curtin University
ABSTRACT
The offshore seismic survey industry typically uses arrays of devices called airguns to generate the intense, low-frequency sounds required for imaging the seabed geology. Concerns have arisen about the impacts that these high intensity sounds may have on benthic species, such as shellfish, site attached fish and crustaceans, that have little or no capacity to move out of the way of an approaching seismic vessel. In order to assess the impacts a survey may have on these species it is essential to have a means of predicting the sound levels they are likely to be subjected to. This paper discusses the characteristics of the sound field beneath a typical seismic airgun array and compares results obtained using some simplistic formulae for predicting sound exposure level and peak sound pressure level, that are applicable in the acoustic far-field of the array, to those obtained using a more accurate model that includes array near-field effects. For the typical medium-sized 49.2 l (3000 in3) airgun array considered here the predicted near-field to far-field transition distance was 14.5 m and a simple equivalent point source model was found to over predict the sound exposure level by 1.1 dB and to over predict the peak sound pressure level by 3.3 dB at this distance below the array. At double this distance these errors had reduced to 0.6 dB and 1.4 dB respectively.
(1) Defence Science and Technology Group (2) Centre for Marine Science and Technology
ABSTRACT
Acoustic energy incident at a roughened seafloor will result in a component scattered back into the water at non-specular angles, a component reflected coherently at the specular angle, and both coherent and incoherent components being transmitted into, and absorbed within, the seafloor. An initial expectation was that the total coherent reflection loss might be approximated by a combination of the loss attributed to a flat seafloor based on its geoacoustic properties, and the separate coherent loss due to the roughness scattering described for a perfectly reflecting surface. This hypothesis had been verified in limited earlier work, by comparing loss values obtained using this simple addition of model outputs with loss values obtained using the perturbation approach for rough surface scattering from stratified media described by Kuperman and Schmidt (JASA, 86, Oct. 1989). In recent work, data obtained using Monte Carlo Parabolic Equation (PE) transmission simulations have been used as the reference.
(1) Defence Science & Technology Group
ABSTRACT
Active sonar relies on the transmission of broadband pulses and correlation processing (also known as pulse compression) to enhance signal-to-noise ratio for detection and to achieve high resolution in range. A pulse transmitted in an underwater channel propagates to a receiver through different multipaths due to refraction (within the water column) and reflection (from the sea surface and bottom). Different multipaths undergo different time-delays and propagation loss. Furthermore, reflections from rough sea surfaces and bottoms also spread and distort the pulses. Therefore the received pulse is spread out in time and distorted in shape. Correlation of the received distorted pulse with a replica of the transmitted pulse leads to a degradation in processing gain in comparison to the ideal case of a received pulse being simply a time-shifted, amplitude-scaled replica propagated from a single direct path. This degradation in processing gain is termed correlation loss. Based on parabolic equation modelling, previous authors studied correlation loss in one-way propagation of frequency-modulated signals in shallow water environments with rough sea surfaces. In this paper, we investigate the correlation loss for environments with both rough sea surfaces and rough sea bottoms. The received signal consists of the convolution of the transmitted signal with the impulse response of the channel. The impulse responses are predicted using Gaussian beam propagation and parabolic equation methods. The results also show that the correlation loss can be reduced if the reference (replica) accounts for the distortion.
Defence Science and Technology Group
ABSTRACT
In this paper, sound trapping in ocean surface ducts is considered for two types of ducts. One type is determined by the isothermal linear sound speed profile, whereas the other type is due to the presence of gas bubbles near the ocean surface. Brekhovskikh [Waves in Layered Media, 1960] published a solution for the acoustic wave equation using hypergeometric series in a transitional layer with a specific sound speed profile. It is shown here that Brekhovskikh's transitional layer can be fitted to sound speed profiles in both types of ducts, and, therefore, the pressure field in the ducts can be described by the wave-based solution developed by Brekhovskikh. The parameters of the fitted layer allow significant simplification of the solution. Based on the simplified solution, a condition of existence of a trapped wave in the duct is obtained. This condition is utilised to calculate the trapping (cut-on) frequencies of the duct modes. These trapping frequencies are compared with the ones obtained by a commonly used equation based on ray theory. Also, vertical pressure profiles for trapped modes at different frequencies are calculated. It is shown that, for each mode at frequencies just above the trapping frequency, an evanescent acoustic field, which does not propagate in the vertical direction, exists below the duct. It is suggested that the evanescent field below the duct may lead to increased energy leakage from the duct.
School of Public Health, Massey University, Wellington, New Zealand
ABSTRACT
With the introduction of the Health and Safety at Work Act 2015, many of the existing health and safety regulations in New Zealand are being replaced. The first suite of new regulations supporting the Act was released by the Government on 15th February 2016 but this did not include occupational noise regulations. This discussion paper considers the direction that occupational noise law in New Zealand may take over the next few years. This paper identifies some of the issues in the translation of the Australian model regulations into the New Zealand context and identifies other gaps that the author thinks needs addressing. It also considers the approach taken with the new 'Asbestos' regulations and whether or not a similar detailed approach should be taken in addressing occupational noise issues. Finally, it proposes that the development of appropriate Safe Work Instruments may be the best way to address many of the issues identified.
Svantek
ABSTRACT
Occupational noise measurement over the full working day is usually performed using personal sound exposure meters (noise dosimeters). As workers carrying a dosimeter inevitably disturb the measurements, (whether willingly or unwillingly), it can be a challenge to validate results and ensure they are representative of the actual occupational noise exposure. This paper reports on a case study of mechanical workshop noise measurement. Evaluation of daily occupational noise exposure is impeded by non-occupational sound source events, for example "faked" increases in noise level achieved by putting the dosimeter immediately adjacent to the working tool and accidental bumps and scrapes of the microphone against solid surfaces. As shown in this paper, with newer generation, "smart" dosimeters, it is largely possible to eradicate such distortions and thereby achieve a better estimate of the actual occupational noise exposure.
(1) Cogent Acoustics (2) National Acoustic Laboratories (3) Vipac Engineers and Scientists
ABSTRACT
Occupational noise and its impact on worker's hearing is very well investigated, managed and regulated in Australia. Depending on the duration of noise exposure, its characteristics and levels, occupational noise can be a source of annoyance, fatigue and hypertension. Additionally, noise causes significant irreversible hearing damage. Ototoxic chemicals in the workplace also affect our hearing and synergistically exacerbate hearing loss when workers are also exposed to a noisy workplace environment. This paper will review literature on several, major ototoxic agents that are commonly used across industries in Australia; the proposed mechanism of hearing loss due to ototoxicity; the limits of exposure; synergistic effect of noise exposure and ototoxic agents; the strategy of noise survey in ototoxic-noise exposure; available control measures; exposure standards; and the need for further knowledge. This paper aims to assist Workplace Health and Safety (WHS) professionals in identifying the potential ototoxic hazards in their workplace and organise hazard management plans to minimise the potential health risk and injury to the workers hearing.
(1) Vipac Engineers and Scientists Ltd, Brisbane
ABSTRACT
The precise description and assessment of high intensity impulse noise can be difficult. Problematic issues are associated with the accurate measurement and prediction of impulsive noise events due to the rapid onset-rates, very short durations, very high peak noise levels (and overpressures) and the non-linear acoustic behavior in the near-field of the source. Furthermore, determining the likely impact on hearing and the auditory system is limited by the current tools available for assessing the actual noise exposure/dose, auditory hazard risk and potential (irreversible) hearing damage. This paper provides insight to the recent developments in the measurement, prediction and assessment of impulsive noise exposure. A review is provided of the relevant standards and guidelines including AS/NZS 1269, AS/NZS 3817, ISO 10843, ISO 13474, ISO 17201 and MIL-STD-1474. Guidance is given on the range of measurement and prediction methods, impulse waveform pressure-time characteristics, relevant noise metrics/descriptors, models of impulsive noise exposure and hearing damage mechanisms. Newly developed electroacoustic and dynamic hearing models are explored, including the Auditory Hazard Assessment Algorithm for Humans (AHAAH) and exposure metrics such as Auditory Risk Units (ARU). The paper is illustrated with a number of real-world examples of the measurement and estimation of noise exposure from a sample of high energy impulse sources. Other emerging influences and synergistic effects due to ototoxic substances, human vibration and extended work-shift periods are investigated. A discussion is provided on effective noise controls and hearing protection measures for the mitigation of high intensity impulse noise. For the future, to minimize potential severe health risk and injury to workers' hearing from impulse noise, we demonstrate the need for further research and innovation.
(1) National Acoustic Laboratories (2) Consulting Occupational Hygienist
ABSTRACT
When technical users realised that the modern 'smart' phone was in fact a sophisticated, pocket-computer, applications rapidly developed for uses other than the simple telephone phone call. Applications range from simple games to sophisticated scientific purposes. With the inclusion of an inbuilt microphone and an easily readable display one of the possible uses as a sound level meter was obvious. This can easily extended into personal noise dosimetry. But how practical and useful is smart 'phone app as a dosimeter? NAL has addressed this in a practical way by developing a noise dosimeter App. Establishing its utility by verifying dosimetry results for precision and accuracy, and for use as a hearing health education tool.
ABSTRACT
The acoustics and vibration committees within Standards Australia have been active over recent years in adopting and revising standards. Much of this work is not obvious to the world outside until there is the announcement of public review document and then the final version of the Australian Standard. This paper will provide a general overview of the operation of Standards Australia in relation to the committees and the introduction of new work projects. The Australian Acoustical Society (AAS) and the Australian Association of Acoustical Consultants (AAAC) have membership on the committees and the AAS has been the lead organisation for some successful projects. A summary of the current and planned activities for some of the committees will be provided along with some of the challenges for the committee members in achieving timely outcomes.
(1) Floth Sustainable Building Consultants
ABSTRACT
In Australia the Green Star and NABERS rating tools contain design criteria that are used to evaluate the indoor acoustic environment of buildings. How do these design criteria compare against those of rating tools, schemes and standards used by other countries? In this paper a comparison is provided between the acoustical criteria contained in the latest versions of a number of green rating tools, schemes and standards used across the World with the aim of identifying potential shortcomings, the associated compliance pathways available for a project and the importance of acoustics for each rating scheme.
(1) TU Kaiserslautern
ABSTRACT
The standards on sound insulation in buildings in Germany have a long tradition starting in 1938. Due to numerous developments in building materials and constructions and changed general expectations for sound insulation during the past years, this year a totally reviewed catalogue on the standard DIN 4109 "Sound Insulation in Buildings" will be published. The standard consists of 4 parts "Requirements", "Verification of compliance with the requirements by calculation", "Building elements catalogue" and "Guidance for testing acoustics in buildings". The presentation highlights the major innovations, such as a new calculation procedure to predict the sound pressure level in habitable rooms, a new method to predict measurement uncertainties as well as a catalogue on requirements on the sound reduction index and the standardized impact sound pressure level inside buildings. Additionally to the DIN 4109 "Sound Insulation in Buildings", there are further regulations in Germany defining requirements on enhanced sound insulation in buildings if higher comfort is requested. The requirements according to VDI 4100 are classified in 3 quality levels from smooth enhanced to high enhanced sound insulation in buildings.
(1) WSP | Parsons Brinckerhoff
ABSTRACT
The Green Building Council has consolidated several rating tools to form the Design and As-Built rating tool (currently v1.1). The rating tool provides up to 3 points for acoustics, one of which is for Acoustic Separation. The credit is achieved under 10.3A when Rw45 walls are specified for 'enclosed spaces'. The AAAC Guideline for Commercial Building Acoustics rates Rw45 as a 'good' level of sound reduction and Rw50 as 'very good'. Alternatively, the credit is achieved under 10.3B using the measured Dw and LAeq to estimate speech privacy. This based on a method from British Standard BS8233. The approaches in 10.3A and 10.3B are not exactly equivalent as they use different descriptors to evaluate acoustical separation performance. Application of 10.3A or 10.3B may not necessarily result in equivalent outcomes for acoustical speech privacy. In this paper, the comparative acoustical speech privacy outcomes from typical constructions of drywalls are compared using the more detailed analysis method provided in Australian Standard AS2822 Acoustics - methods of assessing predicting speech privacy and speech intelligibility. This standard has no reference to single-value acoustic ratings. Instead, AS2822 determines an articulation index (AI), using a ratio of speech and masking noise levels, in one-third octave bands. The AI is a direct measure of speech privacy. The gaps between the approaches in 10.3A and 10.3B are identified using AS2822 and a methodology to bridge these gaps is proposed.
(1) University of Sydney
ABSTRACT
Reverberation is considered a key factor in listener envelopment. Virtual acoustic renderings of architectural spaces presented via multichannel loudspeakers distributed on the horizontal plane provide for improved listener envelopment and immersion relative to conventional stereophonic reproduction. However, with a new 22.2-channel loudspeaker format that has been submitted by NHK for an ITU recommendation, incorporating speakers at various elevations (termed height channels), there are vast new opportunities for the separation and presentation of real world acoustic events in virtual acoustic renderings. In accordance with the 22.2-channel specification, and the recommended application of these height channels, this paper presents the results of an experiment testing the hypothesis that indirect sound delivered from above the listener's head can create a distinct impression of a modelled virtual acoustic space with a tall ceiling. The experimental stimuli were generated using a simple virtual image model of the Grace Cathedral (located in San Francisco), which model allowed the time of arrival of simulated ceiling reflections to be manipulated. Five sound sources, which were anechoically recorded Gregorian chant performances distributed in azimuth angle at ear level, were processed to allow for spatially segregated presentation of indirect sound components (sets of discrete early reflections and global reverberation) via ear-level and height channels. Using the 196-channel hemispherical loudspeaker system in the Spatial Audio Laboratory at the University of Sydney's Faculty of Architecture, Design and Planning, arbitrary spatial configurations of loudspeakers could be employed, enabling the azimuthal angles of subsets of loudspeakers to be held constant while their elevation angles were varied. In particular, this allowed a control condition to be included in the experiment in which all of the loudspeaker signals were presented at ear level. Although clear differences could be heard in several spatial auditory attributes, such as listener envelopment, the most interesting finding in this experiment was in relation to the listeners' ability to recognise the apparent height of the ceiling in the modelled virtual acoustic space. The results have implications for production techniques that take advantage of the 22.2-channel loudspeaker system proposed by NHK, completely surrounding the listener in a three-dimensional space, and potentially providing heightened realism and listener engagement.
(1) UNSW
ABSTRACT
Sometimes, the beauty of a single note identifies a good musician: The initial and final transients are controlled appropriately, as is the harmonic content of the sustained part. This study reports first how several control parameters are varied by accomplished players of clarinet and saxophone. It then uses measurements on a clarinet-playing machine to determine the effects of these parameters independently. In the sustained part of a note, mouth pressure P and lip force F applied to the reed affect both sound level and harmonic content. Further, good players can control the spectral envelope using the vocal tract: peaks in the acoustic impedance of the tract enhance the amplitude of harmonics in the played note at nearby frequencies. The highly salient initial transients produced by good human players have an approximately exponential increase in the amplitude of the fundamental at rates r about 1000 dB∙s−1 that is achieved by varying both the rate of increase in P and the timing of tongue release during this increase. On the playing machine, when P is above the oscillation threshold, initial reed displacement decays quickly after tongue release, but tongue release rapidly changes the airflow into the bore. This initiates an exponential increase in the sound at rates r that can range from several tens to several hundreds of dB∙s−1, and that, over the range used, increase with increasing P and decreasing F. Finishing notes either by decreasing P below a threshold, or by tongue contact with the reed, produces an exponential decay in the final transient. The amplitude of the fundamental decreases exponentially at rates ~400 dB∙s−1 when notes are stopped by human tonguing. This is consistent with the measured bandwidths of the bore resonances, which indicate the dissipated energy. A simple energy accounting model explains the exponential rises and falls in the initial and final transients: A static flow-pressure curve for the mouthpiece has positive and negative slopes corresponding to positive and negative AC conductances respectively. In the playing region, negative AC conductance converts steady pressure from the DC flow into acoustic energy. This oscillatory energy contributes to the energy stored in the reactive components of a resonance in the bore, from which the losses in the bore and the reed are sinks. The energy budget produces the observed behaviours.
Faculty of Architecture, Design and Planning, The University of Sydney, Sydney, Australia
ABSTRACT
In contrast to many educational facilities for which speech intelligibility is a primary concern, special requirements must be met for spaces that have been designed to support education involving critical listening, particularly for multichannel sound reproduction. It is common to find problems here that demand some acoustical retrofit to the designed space, and these problems often require the refined acoustical treatment solutions typically employed to address problems encountered in the control rooms of recording studios. It is also important to consider the potential for updating the deployed sound reproduction system in such spaces to include more exotic options for multichannel sound reproduction, beyond the conventional five-channel format adopted for the distribution of a great deal of audio-visual material, such as that of commercial surround sound media (with the reproduction environment conforming to the recommendation of the International Telecommunication Union). This paper considers two of the functional goals for such educational facilities that are intended for critical listening to reproduced sound, one being to offer an opportunity for students to experience the influence of the acoustical environment upon sound reproduction, and the other being to give students the chance to experience multichannel sound reproduction employing a variety of loudspeaker configurations.
(1) Research Advisor
ABSTRACT
With 'height channels' in multichannel audio reproduction systems becoming more commonplace, there is substantial and growing interest in understanding production techniques for spatially enhancing the listening experiences made available by such systems. When a group of loudspeakers well above ear level are included in a multichannel loudspeaker array, these 'height channels' present opportunities for manipulation of many spatial auditory attributes, in addition to the possibility of controlling the incidence angle of single virtual sources in both azimuth and elevation. The opportunities investigated in the current study are those enabled by the use of elevated pairs of loudspeakers that present spatially extended stereophonic images of virtual sources. The interaural cross-correlation correlation (IACC) for each of a number of recorded string instruments was manipulated for reproduction via pairs of loudspeakers, the shared elevation angle of which could be varied in elevation. The results demonstrate that the perceived elevation of spatially extended stereophonic images of string instruments could be manipulated by IACC adjustment even though the actual elevation angle was held constant for the loudspeaker pair reproducing each spatially extended component of a multi-instrument ensemble.
(1) SLR Consulting, Acoustics and Vibration, Brisbane, Australia (2) Atkins Global, Acoustics, London, United Kingdom
ABSTRACT
SLR Consulting Australia Pty Ltd (SLR) was engaged to model and measure environmental noise emission levels from gas pipeline blowdown events. Noise measurements taken during the events showed the noise to be broadband, steady-state and to have a determined source sound power level (SWL) of 168 dBA. The measured SWL matched theoretical predictions using jet noise equations for supersonic jets, especially at the initial stages of the blowdown with the highest pressure differentials. Far field measurements were also taken at multiple locations with a dominant source noise level reaching 88 dBA measured at a location 2.6 km from the source. This presentation will also discuss the assumptions inherent within the SWL predictions, and proposes an approach to validating the predictions using measured noise data and provided pipeline settings such as pipeline pressure and the gas material properties. The opportunity to measure such a loud environmental noise event also allowed for an investigation into the application of the CONCAWE algorithm in SoundPLAN with regard to noise predictions over large distances from the source, as is commonly required in the context of noise modelling for the gas industry. The results of the investigation into large distance CONCAWE based predictions will also be discussed.
ABSTRACT
Construction sites and mine sites often have strict noise limits during certain time periods, eg. during the night, weekends and public holidays. Site managers would often like to know what is the most activity that can occur on site simultaneously during periods of restricted noise emissions. Using engineering optimisation techniques it is possible to accurately determine the maximum number of fixed plant and mobile equipment that can be operating together at any time while still complying with the noise emission limits. This paper presents the results of determining the recommended fleet quota using Genetic Algorithms as a post-processing technique based on the noise propagation information from proprietary environmental noise modelling software.
NSW Dept of Planning and Environment
ABSTRACT
The NSW Department of Planning and Environment undertakes a significant amount of research into the noise generated by open cut coal mines in order to build the knowledge base and to assist industry and regulators better manage these impacts, both individually and cumulatively. The present paper considers a range of simplified theoretical scenarios as well as examining two empirical studies that were undertaken by the Department to investigate cumulative noise impacts of coal mining activities. Together, these works have been used to test a hypothesis as to whether absolute criteria, or relative criteria (as determined by the NSW Industrial Noise Policy) is the controlling criterion in regulating noise from these premises. Empirical data were collected under a range of meteorological conditions designed to align with 'worst case' scenarios for the propagation of noise and also allowed estimations of individual mine contributions to the overall noise catchments to be made. The conclusion of the present paper is that due to the geographical size of mines, the relative criteria will be the controlling criterion, and attempts to apply the absolute criteria are unnecessary where the relative criterion of surrounding mines is 40 dB(A) or less.
(1) Research Student Griffith School of Environment (2) Lecturer Urban and Environmental Planning, Griffith School of Environment (3) Professor, Griffith School of Environment
ABSTRACT
This paper describes the iterative evolution of noise assessment and management in the NSW coal industry during the last three decades. The volatile and dynamic nature of the global demand for coal has encouraged an increase in coal production resulting in a sustained mining boom since the mid 1980s. Parallel to this boom in coal mining is the growth of community dissatisfaction with noise exposures, and the increased efforts of the noise regulators to design and implement effective noise regulations for the industry (such as the NSW Industrial Noise Policy (EPA 2000)). This paper describes the key factors that have shaped the changes in environmental noise assessment and management of mining operations and how the coal industry has responded.
Global Acoustics
ABSTRACT
Current and proposed open cut mines are usually required via their approval to install real-time noise monitoring systems (NMS) as a noise management tool. In cases where multiple open-cut mines exist in close proximity to noise sensitive receptors, directional noise-monitoring systems (DNMS) are used in order to determine individual contributions from each mine/noise source. However, little independent testing exists comparing the various DNMS available in the market. As NMS are a regulatory requirement, the focus of this paper is testing the effectiveness of three DNMS currently being utilised at open cut mines in NSW at accurately determining the direction and contribution of multiple noise sources in various scenarios.
(1) School of Mechanical and Chemical Engineering, The University of Western Australia, Crawley, Australia (2) Defence Science and Technology, HMAS Stirling, Rockingham Australia
ABSTRACT
A good understanding of the effect of thrust bearings on the vibrational characteristics of a marine propulsion system is vital in order to develop an accurate model of the drivetrain and to implement vibration control. To achieve this it is necessary to have detailed information about the stiffness and damping of the oil layer inside the bearing and the changes that will occur due to the pressure loading of the oil when the bearing is under load. A simple thrust bearing was thus designed and constructed to emulate features that would be found in a conventional thrust bearing. In doing so, it was possible to incorporate four PVDF sensors into the bearing that could directly measure the pressures generated inside the oil under various conditions. Using this setup, the effects of shaft rotational speed and thickness of the oil film on the pressure were measured. In order to simulate axial vibration effects on the pressure, the thrust bearing was subjected to sinusoidal vibration in the axial direction by directly attaching it to an electro-mechanical shaker.
Defence Science and Technology Group
ABSTRACT
The noise levels for large capacity marine diesel engines must meet legislative requirements as a minimum. Depending upon the installation, there may also be additional constraints on level and spectral content. The limited availability of test facilities and low production volumes for this class of engine / installation means that exhaust system testing and development is generally limited to confirmation testing. To address this development constraint, the Defence Science and Technology Group has developed an experimental test bench to measure the acoustic transmission loss performance of exhaust system components representative of large marine diesel engines. This study describes the test bench design, development, instrumentation, data acquisition, and data processing techniques. This capability operates independently of the engine and engine installation with excitation provided by a low frequency speaker. The measurements are at zero flow and room temperature and the implications of this are discussed. The acoustic transmission loss was calculated using the four microphone method (two microphones before and two microphones after the test element). Computer simulation, published data, and on engine test data was used for validation. The experimental capability described in this study permits assessment and development of large scale exhaust system components with or without engine source data at lower cost through a reduction in physical testing of the complete installation.
(1) The University of Western Australia (2) DSTO Group Stirling
ABSTRACT
To study the structural acoustics of propeller-excited marine vessels, the hull and bulkhead, against which the thrust bearing is mounted, are often modelled as a circular cylinder and a cross-section plate. This paper concerns the effects of the characteristics of the cross-section plate on the vibration and radiated sound from the cylinder. The critical aspect is the coupling between the plate and cylinder, as this affects the input power of the excitation force at the plate and energy transfer from the plate to the cylinder and eventually to the radiated sound. The study compares the input mobility, averaged vibration response of the cylinder, and the radiated sound power with respect to the driving force for full-plate and half-plate configurations. Conditions associated with large sound power radiation from the cylinder are assessed through detailed measurement of the distributed sound intensity and vibration on the surface of the cylinder. The results demonstrate the drastic differences in the radiated sound power when different cross-section plates are used, and indicate the importance of coupling between the hull and bulkhead structure for controlling the radiated sound power from the propeller-driven hull-bulkhead structure.
Maritime Division, Defence Science and Technology Group, Melbourne, Australia
ABSTRACT
Pipe systems transporting liquid or gas are widely used in industrial applications and have the potential to transmit significant vibration to surrounding structures and radiate undesirable noise. This paper reviews previously published studies of the generation and transmission of noise and vibration in pipe systems. An overview of the vibroacoustic behaviour of fluid-filled pipes is given based on results from shell models of straight pipes. A simplified model of a fluid-filled beam can be adopted for pipes vibrating at low frequencies and the main elements of this approach are summarised. The fluid-filled beam is commonly implemented as a transmission matrix and one advantage of this method is realistic pipe circuits can be modelled by combining transmission matrices of sub-components such as straight and curved pipes, mechanical and fluid boundary conditions, and active sources. This review concludes with a discussion of research on identifying transmission and source characteristics of pumps.
(1) University of Western Australia (2) Defence Science Group
ABSTRACT
A detailed understanding of the vibrational properties of submerged objects such as submarines is essential in order to minimize sound emission and optimise sonar performance. Complications arise when hollow structures are submerged in water producing loading on one side. Not only does the water dampen the resonances of the structure but the increase in depth also produces mechanical strain within the structure that also changes the resonant frequencies. In previous work the effect of hydrostatic pressure loading on one side of a rigidly clamped plate was investigated. The modal coupling between the water tank and the vibrating plate hindered the ability to model the experimental dependence of the plate's frequency response with the applied hydrostatic pressure. In this paper some results are presented on the effect of static pressure loading produced by air on the plate, removing the complications introduced by fluid loading and modal coupling. The aim of this work is to accurately measure these effects experimentally and identify similarities and any interesting discrepancies with the numerical and analytical models used for prediction.
(1) National University of Singapore / Singapore Technologies Kinetics Ltd (2) Singapore Technologies Kinetics Ltd (3) National University of Singapore
ABSTRACT
In automobiles, booming noise exists typically at low frequencies (< 500 Hz) within the passenger cabin as a result of vibroacoustic coupling. This may cause passenger discomfort and is certainly undesirable. Generally, traditional acoustical treatments are applied in the cabin for passive noise control. However, excessive treatments may be required for effective low frequency noise control. As such, the overall weight of the automobile is increased; affecting its mobility performance. It is, therefore, imperative to explore other options for such purpose. Recently, researchers have demonstrated the potential of membrane acoustic metamaterials in attenuating low frequency noise based on small-scale specimens. For practicality in the industry, it is necessary to consider larger specimens. This paper presents the preliminary experimental findings for two configurations of a large-scale meta-panel with membrane acoustic metamaterial. It is shown that sound transmission loss may be improved at specific frequency range with the inclusion of a membrane layer. Moreover, the acoustical performance is also affected by the stacking orientation of the meta-panel. Further work to understand the dynamic behaviour of the meta-panel and validate the experimental results is in progress.
School of Computing, Engineering & Mathematics, Western Sydney University, Sydney, Australia
ABSTRACT
A new iterative-analytical approach to determining the static behaviour of a cracked rotor has been developed and applied to a statically indeterminate model. The model subjects the cracked shaft to out-of-plane bending due the inclusion of an offset dynamic force. The interaction between fixed supports and the variable shaft stiffness caused by a breathing crack make the model analytically unsolvable. The presented iterative algorithm for determining the breathing state of the crack makes the model analytically solvable for the support reactions and the elastic deflections. The algorithm rapidly converges, requiring typically fewer than 4 iterations to achieve stable results. The breathing response for a particular set of model parameters has been evaluated and is presented.
(1) School of Engineering, University of South Australia
ABSTRACT
Acoustic metamaterials are composite materials with designed heterogeneity to manipulate vibroacoustic waves for e.g. wave steering, resonation, guiding and filtration. Acoustic metamaterial lattices can be designed by which vibroacoustic waves are filtered out within particular frequency ranges called acoustic bandgap (ABG). Such ABG materials exponentially decay the wave's amplitude due to destructive interface of their periodic microstructure. The width and frequency range of bandgap depends on the contrast of constitutive materials and lattice shape and the topology of its irreducible unit-cell. When the wave length is comparable to the lattice periodicity (i.e. unit-cell size) then constructive reflection of wave through stiff scattering material phase (Bragg reflection) opens so-called phononic bandgap. However, it is well known that relatively low frequencies having wave length larger than unit-cell size may also be manipulated through local resonance. Locally resonant acoustic bandgaps (LRABs) can be produced by periodic insertion of resonating inclusions in a background material, which act as internal oscillator and attenuate wave through destructive oscillations at their local resonance frequency. The inclusions may be produced by insertion of a stiff-dense material in a soft-compliant intermediate material relative to the background material. LRABs also maybe produced by periodic attachment of resonating stubs to a uniform slab. In design of ABGs it is normally desired to achieve broadest frequency isolation at lowest frequency range through specified unit-cell size. In this way low frequencies can be manipulated by tiny feature sizes. Topology optimisation of unit-cell has shown to be a great tool for designing ABGs. However, all preceding topology optimisation studies have been concerned with design of phononic bandgaps, and design of LRABs have been limited to parametric study of prescribed unit-cell designs. In this paper optimised topology of bi-material LRABs is investigated through a multi-objective optimisation framework and the capability to design structurally worthy ABGs with locally resonant features is shown.
(1) School of Computing, Engineering and Mathematics, Western Sydney University, Kingswood, Australia
ABSTRACT
Examining the cross-section of a shaft that has ruptured due to fatigue often reveals beach markings that can be approximated as being elliptical in shape; as such, the front of a crack can be modelled as an ellipse. In this study, an existing elliptical crack model was improved upon to study cracks with a range of elliptical-front crack shapes. The area moments of inertia of the total uncracked area of the shaft were calculated for a number of crack depths and crack curvatures, where it was seen that cracks with greater curvature resulted in stiffer shaft models. The development of the area moment of inertia models serve as a preliminary step for obtaining the time-varying stiffness matrix of cracked shafts with differing crack curvature and to consequently obtain the dynamic behaviour of these rotor systems.
Marshall Day Acoustics Ltd
ABSTRACT
In New Zealand, commercial scale wind farms require resource consents where environmental effects, including noise, are considered. Conditions of consent prescribe noise limits and management and assessment methodologies which apply to the project under consideration. As experience with wind farm noise has accumulated, these conditions have become more complex. In 2010, the second edition of New Zealand Standard NZS6808 was released, which included a model set of conditions intended as a simple and robust set of requirements, when used in conjunction with the standard itself. This paper examines the degree to which subsequent wind farm consents have adopted and relied upon the Standard and the model conditions, and considers whether additional consent conditions that have been included point to matters which should be incorporated into the next edition of the standard.
Arup, Brisbane
ABSTRACT
QUT's Creative Industries Precinct Phase 2 co-locates the music, dance, performance and visual arts portfolios of the Creative Industries Faculty in a mixture of new-build and adaptive re-use of heritage structures. The acoustic design of CIP2 was of primary importance to the overall building performance and posed significant design challenges. Building acoustic design included high sound-insulation separation requirements between music studios, particularly the two professional-quality recording studios and small/medium rehearsal rooms, as well as the design of open-plan office spaces connected by a full-height atrium and secondary voids in order to provide sufficient acoustic privacy between floors and reduce disturbance to office areas from student common areas on floors below. As part of the briefing study, auralisation was used to negotiate project-specific design criteria for the studio spaces based on the requirements of the end-users, resulting in significant cost savings to the building façade for dance and drama studios which did not require high levels of external noise control. A key design challenge was the low-noise mechanical services system for the recording studios, which used a non-traditional system including flexible ductwork which provided significant challenges in achieving the required services noise levels and in controlling crosstalk and duct-breakout between adjacent studios.
(1) Aurecon
ABSTRACT
Doha Oasis theme park is a 25,000 sqm theme park located within a wider mixed use development comprising retail, residential, hotel and four basement carpark levels. The theme park has an elliptic footprint and is enclosed around the perimeter. The theme park is being constructed on a suspended reinforced concrete slab and as such the potential for rides exciting the structure was assessed with regard to both perceptible vibration and structure-borne noise. Airborne noise generated from ride mechanics and patrons was also assessed within the enclosed environment. This paper presents a review of the methods used and the treatment proposed to control noise and vibration within the theme park and from transferring to more sensitive environments adjoining the theme park.
(1) School of Engineering, RMIT University, Melbourne, Australia (2) School of Electrical, Mechanical, and Mechatronic System, University of Technology Sydney, Sydney, Australia (3) School of Architecture and Design, RMIT University, Melbourne, Australia (4) Melbourne School of Design, University of Melbourne, Melbourne, Australia
ABSTRACT
This paper reports on a preliminary investigation of the sound field properties inside a large Roman Catholic Church in Barcelona, the Sagrada Familia Basilica, which is a world heritage site although its construction has not been completed. The impulse responses were measured at five sound source positions combined with 14 measurement locations inside the Sagrada Familia Basilica, and the Impulse response to Noise Ratio (INR) were examined to examine the reliability of the measured impulse responses. The room acoustic parameters were calculated and the following five sound field properties in the Sagrada Familia Basilica were analysed: reverberation, spaciousness, loudness, warmth and clarity. The reverberation time (T20) and the Early Decay Time (EDT) were compared with the existing optimal values for small volume churches whereas the middle frequency strength of sound (Gmid), the low frequency strength of sound (G125), the clarity (C80) and the binaural quality index (1 - IACCE) were compared with the optimal values for concert halls. The understanding of the sound field properties in churches, especially in a church of such a large volume as the Sagrada Familia Basilica, is still an open topic and much further research is necessary for a more thorough understanding.
(1) Acoustic Studio Pty Ltd (2) Bruel & Kjaer
ABSTRACT
Construction activities such as demolition and excavation can generate significant structure-borne and ground-borne noise impacts on nearby receivers. Management of construction noise and vibration often includes the use of loggers equipped with communication capability to provide alerts and alarms when levels approach or exceed pre-determined thresholds. Suitable loggers are now widely available for monitoring airborne noise and providing real-time alerts. Similarly, several vibration loggers are available for monitoring ground or structural vibration. This paper deals with the issue of monitoring structure-borne and ground-borne noise from construction projects. Noise loggers are not well suited to this task because the affected location is within a building, where ambient noise from occupant activity often significantly exceeds the applicable criteria for ground-borne noise. Existing vibration loggers are not well suited to this task either, because they focus on assessment against criteria for structural damage and/or human comfort, both of which involve different frequency ranges, metrics and amplitudes of vibration than those that give rise to structure-borne and ground-borne noise. This paper presents a ground-borne noise monitoring method based on the "indirect measurement method", derived from the vibration velocity measured at (or near) the affected receiver, together with a transfer function to account for vibration transmission and radiation of noise within the receiver space.
(1) SA Environment Protection Authority
ABSTRACT
The Adelaide Central Business District (CBD) has been facing densification due to an increase in the growth of residents and business in the area. Noise is considered by the residents of the city as one of the major problems impairing the amenity within the CBD. This has raised multiple concerns such as health and sleep disturbance. Further growth of business activities and an increase in the number of residents in the city is expected in the coming years. This may lead to increased noise impact in the Adelaide CBD and adjacent areas. This paper details strategic noise mapping based on predictive modelling coupled with indications of six noise monitoring stations deployed over a long term period. The noise monitoring stations were located strategically in the northern part of the Adelaide CBD to capture noise impact from several major noise sources. This allowed for detailed analysis of noise contribution from various noise sources. Some of the CBD areas characterised by higher noise levels are targeted for comparison with population exposure descriptors and factors. The results of this study can be utilised for effective noise management and urban planning decisions to reduce noise impact in the city.
(1) Brisbane City Council
ABSTRACT
Government authorities are faced with a number of challenges when attempting to regulate noise from outdoor concerts. A key difficulty is the ability of an authority to meaningfully influence the behaviour of a concert operator during the concert itself. In many jurisdictions, penalties for environmental noise nuisance are an insufficient deterrent - resulting in permit conditions and noise limits being routinely exceeded. Authorities can also face a regulatory burden where noise conditions are technically difficult to measure, difficult to determine compliance, and require specialised equipment and staff to be available outside standard business hours. This paper presents a refined noise management approach to address these issues that has been demonstrated to result in improved compliance from industry and reduced community complaints. Industry behaviour has been improved by applying permit conditions that provide incentives for good industry self-regulation. Noise limits have been carefully determined with the aim of motivating good noise self-regulation without being prohibitively punitive or impractical. Noise limits need to consider the realistic sound levels that are needed to hold a successful concert, while still preventing unreasonable impacts. The concert operator is effectively compelled to actively monitor their own noise levels throughout the concert in order to maintain compliance. This strategy has been implemented most effectively by setting noise measurement locations at the sound mixing desk. Mixing desk staff can then monitor their own levels with immediate feedback and corrections where required. Self-monitoring provides industry with the ability to clearly demonstrate responsible behaviour to authorities and the community and provides certainty and security for the future of the venue and industry. Case studies from outdoor concerts in Brisbane will be presented to illustrate these improvements.
(1) Curtin University Centre for Marine Science and Technology
ABSTRACT
The emerging field of underwater acoustic communication networks is under-pinned by accurate knowledge on the time-varying distortion of acoustic signals by the ocean. This paper reports on time-varying underwater acoustic channel responses measured over ranges of 100m to 10km in 50m deep water south-west of Rottnest Island, Western Australia, for 9-15kHz band signals. The channel response measurement techniques are described, including post-processing by correlative channel probing. The measured channel response spreading function is presented which conveys the spectrum of Doppler frequency shifts imparted by the ocean environment to transmitted data signals.
(1) Defence Science and Technology Group (2) Centre for Marine Science and Technology
ABSTRACT
For underwater sound transmission in a mixed-layer surface duct, the trapping of sound and the coherent leakage of some of this energy from the duct are well known phenomena. Models of sound transmission which include wave effects, such as modal models or Parabolic Equation models, include implicit determinations of the rates of coherent leakage. However for some applications it is useful or instructive to obtain direct analytic determinations of the leakage for practical combinations of sound speed gradient in the surface duct and below the duct. Work carried out by the authors on the derivation of an approximate algorithm for the rate of coherent duct leakage is reviewed, with comparisons with leakage rates determined by a wave-type model for several surface duct scenarios. Also the practicality of incorporating this determination of leakage within a ray model of transmission is illustrated by comparisons of received level at various ranges and depths obtained from a wave-type model versus those obtained from a ray model which includes the leakage expression.
(1) DST Group
ABSTRACT
There is of interest in some defence applications to develop a model of a bubble cloud generated by an underwater explosion. The ultimate purpose of such a model is to simulate response of the bubble cloud to an active sonar pulse. For this, one needs to know the size distribution of the bubbles resulting from the disintegration of the initial explosion bubble. The bubble size distribution in the remnant bubble cloud is not static and is changing with time due to the rise of bubbles to the surface, bubble coalescence and break-up. The problem of the rising bubble cloud is mathematically simpler than the problem of the explosion bubble disintegration into smaller bubbles, but is still too complex to solve it analytically. The complexity of the multiphase flow in the rising bubble cloud is caused by the presence of the bubbles of many different sizes and their interaction with each other, mainly through the water entrained by the bubble motion. A previously developed model did not take into account the motion of entrained water and its influence on the bubble rise. However, it is obvious that the water entrained by the larger bubbles makes smaller bubbles rise faster, thus affecting the dynamics of the bubble size and spatial distribution and, therefore, the time history of its acoustic response. For further improvement of the model of the rising bubble cloud it is necessary to develop a computationally efficient model of water entrainment by large bubbles. The paper will describe such a model and the supporting experiments in an acoustic tank using a small air gun. During the experiments high-speed videos of the initial bubble were taken, the acoustic transmission through the bubble cloud and the velocity of water in the rising bubble cloud were measured. The results of the improved model will be compared with the results of experiments and high-fidelity CFD simulations.
(1) VicRoads
ABSTRACT
In 2015, VicRoads commenced a programme to monitor the environmental performance of Melbourne's road network. Three freeways and three arterial roads were selected across metropolitan Melbourne for the installation of noise and air quality monitors. The locations were chosen for their representation of major roads in Melbourne, the availability of actual traffic data and the lack of interference from other sources of pollution. Hourly noise levels are collected continuously and NO2 emissions are measured by means of diffusion tubes. The monitoring programme is detailed here and results with preliminary findings from the first months of noise monitoring are introduced.
(1) Queensland Department of Transport and Main Roads (2) SLR Consulting Australia Pty Ltd (3) GIS People Pty Ltd (4) MRG Environmental Pty Ltd
ABSTRACT
Detailed noise modelling of approximately 34 850 km of major roads and 3 100 km of railways in Queensland, Australia was conducted to support decision making processes for residential buildings in transport noise corridors under the Queensland Development Code (QDC). The modelling is believed to be the largest project of its kind undertaken in the world to date. The project replaces earlier modelling that did not consider terrain and barrier effects, potentially resulting in conservative acoustic requirements for buildings. SoundPLAN software managed high resolution terrain data using a tiling methodology and calculated noise levels on a fine grid. GIS software then produced the required noise category contours from the modelled results. Preliminary analysis of the detailed road modelling shows that the numbers of properties within QDC noise category 4 and noise category 3 mandatory noise corridors were reduced by 28% and 7% respectively State-wide. This should result in significant savings for new residential development. Work has commenced on a second stage of modelling incorporating additional high resolution data. This paper describes the modelling methodology, summarises challenges, issues and solutions, and presents a preliminary analysis of results.
(1) RIVM, Netherlands (2) Griffith UNiversity, Brisbane
ABSTRACT
This paper describes a systematic literature review (1980-2014) of evidence on the effects of transport noise interventions on human health. Sources considered are roadways, railways, and air traffic. Health outcomes include sleep disturbance, annoyance, cognitive impairment of children and cardiovascular diseases. The interventions reviewed covered all noise management or control strategies practiced for all sources of transport noise. A previously developed model was applied to categorise studies (1). The review shows that evidence is thinly spread across different sources, outcomes and intervention types. While meta-analysis of the association between changes in level and outcome was not possible, some 43 individual transport source studies were examined as to whether the intervention lead to a change in health outcome and (for source, path and infrastructure change interventions) if the observed change in outcome was of a magnitude at least equivalent to that which would be predicted from a relevant exposure-response function, or exhibited excess response. The review showed that diverse intervention study designs, methods of analyses, exposure levels, and changes in exposure, restricted the analysis of findings. Further studies of transport interventions should be based on a protocol of measuring change in exposures, outcomes and confounders, not just changes in noise levels.
(1) Resonate Acoustics
ABSTRACT
With the increase in wind energy projects in Australia over the past decade, most Australian States now have a wind farm noise assessment procedure either approved or in draft. Given that wind turbines operate under windy conditions and vary in noise level with the wind, these procedures necessarily vary from typical noise assessment methodologies applied to industry and transport sources. While there are differences between the wind farm noise assessment procedures within each State, in all cases the methodologies employed for the assessment of overall A-weighted noise levels are based on a modified version of that prescribed in the UK document ETSU-R-97 The Assessment and Rating of Noise from Wind Farms. With a higher level of attention around wind farm noise in comparison to other environmental noise sources and with some proposed assessment procedures in draft format, it is prudent to review these assessment procedures and consider their suitability. This paper reviews the approaches taken in the procedures to the assessment of wind farm and background noise, establishment of assessment criteria and the consideration of wind farm noise character. It is demonstrated that, while the assessment methodologies may appear fairly similar, relatively minor differences in procedure can have a significant impact on a noise assessment or developed noise objective.
Sonus
ABSTRACT
The noise at residences from wind farms is often lower than the noise from other sources and this presents significant challenges in noise compliance monitoring. Further, there has been a focus on the accuracy of noise compliance monitoring in the media and this highlights the need for the most accurate method of compliance monitoring to be adopted. This presentation describes a number of techniques recently used to monitor noise compliance at various wind farms to overcome the inherent challenges of separating wind farm noise from the noise of other sources.
ASNZ
ABSTRACT
A minimum level of inter-tenancy sound insulation is specified in clause G6 of the current New Zealand Building Code. The code was introduced in the early 1990's and clause G6 has not been substantially revised since its introduction. This brief paper describes two recent sound insulation test results in light of a recent determination regarding the applicability of clause G6, and a recent proposed revision to clause G6.
(1) TU Kaiserslautern
ABSTRACT
In buildings more and more equipment for HVAC is used, while it produces noise, it can be annoying. Since noise is one of the most disturbing factors in buildings, the characterisation on structure-borne sound sources as well as knowledge on the vibration propagation in the building structure are necessary. The vibration propagation is already rather good investigated. However the characterisation of structure-borne sound sources isn't done yet. Such as, the standard EN 12354-1 and similar national standards only provide little information regarding the characterisation of a structure-born sound source. Especially for light-weight constructions, detailed information on structure-borne sound sources are needed, because a high sound pressure level may occur when the mobility of the source matches with the receiver mobility. This paper describes investigations on the characterisation of structure-born sound sources by using the two-stage method. The method based on a laboratory-based measurement procedure by using both a high- and low-mobility reception plate to get knowledge on both the source activity and mobility. Results on measurements on different sources are presented. The specific source parameters free velocity and effective mobility were detected. Using these parameters the structure-borne sound power level was calculated and compared with measured values of the sound power level. Furthermore the influence on different reception plates was investigated. Additionally to that, a discussion on the uncertainties of the two-stage method was conducted. The results are compared with the uncertainties provided by the standard EN 12354.
(1) Member AAS
ABSTRACT
Gyms are a common source of complaints for adjacent tenancies due to noise and vibration issues. In many cases it is impractical to install a concrete floating slab and therefore lightweight floor options are increasingly being used for retrofitting, due to cost effectiveness and ease of removal for change of tenancy. Difficulties arise when selecting suitable lightweight gym floor build-ups to achieve satisfactory noise and vibration reduction. This paper presents test data results for noise and vibration levels of low and high density rubber installed directly onto a suspended slab, rubber mounts under plywood with a rubber top surface and damped spring mounts under plywood with a rubber top surface. This paper further presents a comparative test performed between plywood and compressed fibre cement on damped spring mounts. A 10kg kettlebell was dropped ten times from 620mm height for each lightweight gym system and a Svantek 958 Analyser was used to record noise and vibration levels for each impact. High density rubber installed onto the slab achieved the lowest improvement of 9dB(A) while damped spring mounts under plywood had the most significant reduction of 31dB(A). The damped spring mounts under plywood also provided the highest vibration isolation with a weighted single RMS value of 0.026m/s2 compared to 0.071m/s2 of the bare concrete slab while the low and high density rubbers increased vibration levels. The secondary study indicated that the use of compressed fibre cement provided significantly improved performance in noise and vibration.
(1) Day Design Pty Ltd
ABSTRACT
The majority of complaints by residents in multi-dwelling residences are caused by impact noise. This study attempts to investigate the influence of various flooring products and resilient underlays on the impact sound isolation of several commonly used floor systems. The impact sound insulation of numerous combinations of flooring products and resilient underlays were tested on a concrete slab with a plasterboard ceiling. The flooring products tested were an engineered tile system, engineered timber, timber laminate or vinyl flooring products. The underlay products consisted of three rubber underlays with varying thicknesses, one underlay consisting of polyurethane foam granulates and cork and an underlay consisting of polyurethane-bound elastomers. Comparison of results between soft floor coverings and hard floor coverings indicate that the profile of the resilient underlay can have significant improvements in impact sound insulation, more so than the weight of the flooring or the thickness of the material.
(1) Brisbane City Council
ABSTRACT
Prevention is always better than cure when managing noise impacts. Trying to resolve noise problems after they occur may not always be possible and is often difficult and costly. It is therefore important to design out problems by good planning. This paper will identify how the Brisbane City Plan 2014 has been used to design out noise problems upfront in the strategic planning for the city and during the assessment of individual development applications. It will cover the policy approach and rationale behind the noise criteria and planning instruments used in the Brisbane City Plan 2014 to protect noise-sensitive uses from industrial development and also to protect existing industrial activities and future residents from encroaching noise-sensitive development. The Brisbane City Plan 2014 includes noise planning criteria that is separate from the regulatory criteria used for investigating noise complaints or licensing activities. It utilises planning instruments such as zoning and overlay maps to identify noise affected locations. It links noise planning criteria to the specific land use zones thereby recognising that not all parts of the city have the same acoustic environment. The noise planning criteria uses prediction of the LAeq 11hour (for the day period), LAeq 4hour (for the evening period) and LAeq 9hour (for the night time period) to identify potential intrusive noise impacts, rather than the traditional approach of using LAeq 15 minutes. It also uses prediction of the LAmax values relative to the existing ambient noise levels to assess potential impacts on sleep disturbance. New noise-sensitive uses encroaching on existing industry are required to incorporate building design and construction measures to achieve indoor noise criteria, but not outdoor criteria. This paper will use the Brisbane City Plan 2014 as a case study to illustrate the development and implementation of contemporary environmental noise policy.
(1) EPA Victoria
ABSTRACT
Environment Protection Authority Victoria (EPA) and the Department of Environment, Land, Water and Planning (DELWP) are currently reviewing the [Victorian] State Environment Protection Policies (SEPPs) for noise; State Environment Protection Policy (Control of Noise from Industry, Commerce and Trade) No. N-1 (SEPP N-1) and State Environment Protection Policy (Control of Music Noise from Public Premises) No. N-2 (SEPP N-2). The process of revising these SEPPs (which have not been materially revised since the late 1980s) has presented a number of challenges. With increasing urbanisation, consolidation of major industries and the emergence of new noise sources and sound technologies the noise landscape in Victoria has changed significantly over the last few decades; the review of the SEPPs has taken into account these changes and has also considered likely future developments. Community expectations have also changed over time and the review has attempted to balance the expectation of protection from unreasonable noise with the setting of clear, realistic and achievable standards to support business to meet its obligations. A key part of the SEPPs review has been to address the issue of regulatory responsibility between state and local government bodies in managing noise issues. The overlap of regulatory powers between government agencies associated with the existing SEPPs has created uncertainty for businesses and the community, particularly related to compliance and enforcement. The review has sought to clarify these roles and in doing so improve the effectiveness and accessibility of these policies.
Retired
ABSTRACT
The regulation of environmental noise has proven elusive and complex, as reflected in the various approaches that have been adopted over the past 50 or so years. These regulatory challenges can be attributed to the vast array of potential noise sources needing to be controlled, the diversity of likely community impacts and reactions they may cause, and the range of possible noise management strategies that can be employed. Efforts to regulate environmental noise can be identified in such instruments as regulations approved by State parliaments; in policies and guidelines; in local laws; in special exemptions; and in conditions imposed on environmental notices, licences, approvals and legal judgements. Innovative approaches are therefore needed if environmental noise regulation is to be efficient and effective in the future. A framework is presented for the regulation of environmental noise, based on three key elements: protection, fairness and certainty. In relation to protection, this paper briefly reviews current research on the effects of environmental noise, and outlines the issues around what is to be protected, under what circumstances and to what extent. While aiming for appropriate protection, it is also necessary to optimise fairness and certainty of outcome - for both the noise emitters and receivers - requiring that a balance be struck between all three elements. The framework is applied through various examples drawn from the author's noise regulatory experiences, including transportation noise, blasting, noise from recreational activities and noise from wind farms. The framework is intended to assist, not only government regulators, but any who have input into environmental noise regulatory processes.
DCNS Research, Technopole de la Mer, 83190 Ollioules, France
ABSTRACT
Contrarily to airborne acoustics where many documents have been made available for different purposes for a long time, no standard was available for underwater acoustics until now. One of the main reasons is that most of the topic was in relationship with military purposes, each Navy using its own procedures while keeping confidentiality. The increasing development of anthropogenic activity at sea (shipping, marine renewables, oil and gas survey, other industrial exploitation) combined with the awareness of bio-acousticians regarding environmental impact and protection of marine life changes the context. There is currently a consensus among stakeholders (scientists, industry, government representatives and policy makers) to have at one's disposal some internationally approved standards for underwater acoustics. After a reminder of the role of standardization, not to be confused with regulation, the purpose of this paper is to present the current status and on-going actions, most of them conducted at international level under the auspices of the ISO TC 43-3 committee. The priority topics, corresponding to documents already published or pending are: measurement of radiated noise level from ships in deep waters, terminology for underwater acoustics, and measurement of sound emitted by pile driving. Some other working groups are active or foreseen within a few years.
(1) DSTG (2) DSTG/ UWA
ABSTRACT
Development of a compact underwater sound intensity sensor based on the "two hydrophone" (or 'p-p') principle would be very useful for many underwater applications. Attempts to developed sound intensity probes based on the combination of particle velocity and pressure sensors have been reported by some authors but their suitability for use on a moving platform is unconvincing. Our previous work was focused on using piezoelectric PVDF polymer films to construct such a p-p sound intensity sensor. This showed some promising results but difficulties arose in compensating for the directivity of the individual pressure sensor films. Ideally these should be omni-directional in order to accurately estimate the sound pressure gradient using the finite difference approximation. By using anisotropic backing materials it has been possible to control the directionality of the PVDF films up to frequencies as high as 50 kHz. The effect of various substrate anisotropies on the directionality will be discussed.
DST Group, Australia
ABSTRACT
Over recent years, the processing power of single-board microcontrollers has increased significantly. These microcontrollers are low cost, have a small footprint, use relatively small amounts of power and are able to interface with a multitude of different devices. One such microcontroller is the Beaglebone Black. In this work we test the current limits of a Beaglebone Black acting as a portable, real-time, multi-channel, sonar signal processor. By interfacing analogue-to-digital converter chips to the open-source microcontroller, running open-source software, we show that it is possible to process high resolution, high sample rate, hydro-acoustic data in real-time.
(1) Griffith School of Environment/Urban Research Program (2) Acoustics Group, Dept Information Technology, Ghent University, Belgium (3) Griffith School of Environment
ABSTRACT
A key question for road traffic noise management is whether prediction of human response to noise, including sleep quality, could be improved over the use of conventional energy equivalent, or percentile, measures, by accounting for noise events in road traffic streams. This paper reports initial results from a noise-events investigation into event-based indicators over an exhaustive set of traffic flow, traffic composition, and propagation distance, conditions in unshielded locations in proximity to roadways. We simulate the time-varying noise level histories at various distances from roadways using a dynamic micro-traffic model and a distribution of sound power levels of individual vehicles. We then develop a comprehensive set of noise event indicators, extrapolated from those suggested in the literature, and use them to count noise events in these simulated time histories. We report the noise-event algorithms that produce realistic, and reliable, counts of noise events for one-hour measurement periods, then reduce redundancy in the indicator set by suggesting a small number of representative event indicators. Later work will report the traffic composition and distance conditions under which noise event measures provide information uncorrelated with conventional road traffic noise indicators - and which thus may prove useful as supplementary indicators to energy-equivalent measures for road traffic noise
(1) Director, Acoustics RB Pty Ltd (2) Senior Engineering Technician, Acoustics RB Pty Ltd
ABSTRACT
Historically, the extent of intrusion of road traffic noise at residential locations has been quantified by the L10(18hour) noise level parameter. Well-researched prediction algorithms exist for this parameter. Various regulatory authorities set standards for acceptable levels of road traffic noise emission in terms of many other noise level parameters as well (eg. LAeq,1hr night). There are, however, few if any validated prediction algorithms for any of these other noise level variables. Rather, the most practical means of making accurate predictions has been to condense all of the alternative parameters to equivalent L10(18hour) values and use the lowest L10(18hour) value to set the acceptance standard. This paper extends work that was conducted in 2004 on this matter by one of the authors. It examines the results of continuous noise level monitoring at a large number of sites and combines these results with the dataset of the results used for the original evaluation with the objective of further refining the relationships between the alternative parameters and the L10(18hour) parameter. The practitioner, when confronted with the requirement to make predictions of the extent of road traffic noise intrusion in terms of parameters other than L10(18hour), may then make use of these updated results to establish a first order assessment of the likely equivalent predicable L10(18hour) value which may be used instead of the non-predictable alternative variables.
(1) SLR Consulting
ABSTRACT
The prediction of road traffic noise using noise models is a common feature of Environmental Assessments and Development Applications. The outputs of noise models are used to determine the requirements for noise mitigation for a project, which can easily amount to several million dollars in value on large projects. It is therefore important to have reliable modelling results which adequately represent a project's impacts and that correlate well with noise levels measured in the real world. Road surface corrections have been measured using SLR's innovative 3D printed On-Board Sound Intensity (OBSI) system for the eastbound and westbound carriageway of a test section of the M4 Motorway. The OBSI road surface corrections have been applied to a noise model and compared to the use of 'standard' road surface corrections. The noise predictions in both scenarios have been referenced to noise monitoring data at nine locations within the study area. The results of the modelling show that the predictions which make use of the OBSI road surface corrections correlate better with the measured noise level data when compared to the scenario using 'standard' corrections. The OBSI corrections were found to improve both the median error and the standard deviation of the dataset.
Marshall Day Acoustics
ABSTRACT
In New Zealand and Australia, we are about ten years into a renaissance of 'open plan classrooms'. In contrast to the failed experiments of the 1970s, there is greater (but by no means universal) optimism that these new Innovative Learning Environments (ILEs) can be made to work. This paper sets out the known acoustical challenges that arise in ILEs and how they can be overcome. One of the most important messages is that an ILE with even the most ideal acoustic design will still fail unless it is set up and used in the appropriate way. This means two things: (1) The various design aspects of an ILE simply cannot be progressed independently. There must be a collaborative and even-handed approach towards all design aspects, and the consequences of getting this wrong in learning spaces are more severe for the end users (the teachers and pupils) than in other building types. (2) There is a need to educate school managers and teachers so they understand the limitations of the space and how to make use of its benefits. This is not an acoustical issue, but the acoustical design will be seen as deficient unless teaching and management practices that are suitable for the space are adopted There are many pieces to this puzzle, and we understand what the picture should look like now more than ever before. The stakes are high and it is hoped that this paper can set help the scene for architects, policy makers, educationalists, teachers and acousticians, so that we move forward with a common understanding of how ILEs need to be designed, and how renovations of existing classroom blocks into ILEs should be approached.
Norman Disney & Young
ABSTRACT
Childcare or young education centres are being built in close proximity of intermittent noise sources such as helipads of hospitals, railway lines or non-commercial airports. Due to the nature and occurrence of this type of noise, no current regulations or standards are available to use as design guidelines. Research indicates that, compared to adults, children may be more prone to the adverse effects of noise, due to the lack of ability to control the environment. In addition, they are more susceptible to the impact of noise. Unfortunately, little is known about the impact on babies and young children's health and well being for once a day or once a week noise events. However, high noise levels have been proven to cause sleep disturbance, higher stress levels and learning disadvantages for young children. Based on available guidelines and research, this paper recommends that maximum noise levels are determined as design standards for new child care centres located in close proximity to intermittent noise sources for once a day or once a week events. The paper recommends that internal noise levels should be limited to minimise sleep disturbance and impact on noise induced hearing loss.
(1) School of Public Health, Massey University, Wellington, New Zealand (2) Phonak NZ Ltd
ABSTRACT
The Ministry of Education in New Zealand has a policy of upgrading all classrooms into Flexible Learning Spaces (FLSs) or Innovative Learning Environments (ILEs) by 2021. These are open-plan learning spaces where multiple 'classes' operate under the same roof and teachers cooperate with one another to task-share their lesson plans and the students can carry out set tasks in a range of environments. Careful acoustic design is required for these new spaces with large amounts of acoustic absorption to manage reverberant build-up of activity noise. New Zealand schools invested significantly in soundfield technology over the past 15 or more years. The aim was to the raise sound level of the teacher voice above the background noise level so it they can clearly heard by all students in the room. A significant number of studies have shown the benefits of this technology for a wide range of students. However, this technology cannot be deployed in the ILEs because these are shared spaces and the sound reinforcement in one area of the space results in an increased background noise level in other areas of the shared space. While there are many attributes promoted for flexible learning spaces, problems of high noise levels, distraction and over sensory stimulation, are a significant issue. This paper considers other technical solutions that can help restore the benefits of soundfield technology or at least mitigate the negative acoustics of ILEs. Possible solutions include assistive sound technology, were a wirelessly linked teacher's microphone, directly transmits their voice to a hearing aid like device worn by the students.
Macquarie University and National Acoustic Laboratories
ABSTRACT
Children spend 45-75% of their time in the classroom listening to their teacher and classmates. As current teaching methods have a strong focus on group work activities, contemporary classrooms are prone to high noise levels. Therefore, the classroom acoustic environment needs to be designed appropriately. The AS/NZS2107:2000 standard currently has recommendations for unoccupied classroom ambient noise levels and reverberation times, however, these are not enforced. Furthermore, there are no recommendations for occupied classroom acoustic conditions. Therefore, the aim of this paper was to review current classroom acoustic standards and recommendations around the world, summarise typical noise levels found in classrooms, and provide recommendations on the unoccupied and occupied classroom acoustic conditions needed for children at different ages and children with special educational needs.
(1) Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology
ABSTRACT
Holes and gaps are often found at the cracks in walls or the conjunctions between structural elements, as a result of manufacturing deficiencies or functional purposes. The airborne noise transmitted through those channels could make a considerable effect upon the sound insulation performance of the structures and increase the noise level in the receiving field. Despite the extensive efforts made in the past to study the sound transmission characteristics of a hole in a wall of finite thickness, there remain questions to which proper answer should be given. For example, the negative sound transmission loss value in the frequency regions associated with the resonance frequency of the fluid-loaded hole is an apparent violation of the power conservation. Such a result may confuse the understanding of the transmission process because the sound, instead of being reduced, tends to be amplified in the course of transmission. The occurrence of this phenomenon would be explained in this paper using a simple one-dimensional model. The sound intensity field at the incidence side shows that the hole essentially draws energy from a region much greater than its physical dimension around the resonance frequencies of the fluid-loaded hole. At off-resonance frequencies, the way in which energy flows into the hole is found to depend upon whether the coupled system is stiffness-like or mass-like. The model is then extended to the case in which the hole is filled with an acoustic seal. Results show that the acoustic seal would improve the sound insulation to a large extent at the off-resonance frequencies, while poor insulation performance is noticed around the resonances, the frequencies of which are determined by the depth of the hole.
(1) Scion (2) Knowles Consulting Ltd (3) Pryda NZ Ltd (4) Marshall Day Acoustics (5) MiTek NZ
ABSTRACT
A connection system was developed to provide structural load transfer between multi-residential units without compromising acoustic performance. The primary application of the system is to connect the frames of double-stud inter-tenancy walls found in terraced housing, transferring horizontal seismic and wind loads. Such a connection system makes available more options for designers, enabling taller light-framed systems to be built with fewer design compromises. The connectors were designed to have a high degree of structural connection when a building is under extreme external loads from seismic events or extreme wind events. However, under normal conditions the connectors provide less structural connection, giving better acoustic isolation between units. The design of the connectors is examined, and the acoustic and structural performance test results presented.
ABSTRACT
For the assessment of speech privacy and speech security, a uniformly weighted 1/3-octave-band signal-to-noise ratio, clipped to -32 dB, has been found to be a good indicator of speech intelligibility, cadence and audibility. A parameter required in the determination of the ratio for a listener in an adjoining room to the speech source is the average sound transmission loss of the separating construction. A prediction model for the average sound transmission loss of steel stud partitions has been developed and will be discussed.
(1) Auckland University of Technology
ABSTRACT
The paper is about modelling a lightweight double plate structure having two plates attached by a set of beams placed at a fixed distance, i.e. a periodic structure. The structure is of finite dimension and is considered to be simply supported on its four edges. The cavities formed by the beams and the plates are treated separately instead of considering a single cavity between the two plates. The plate displacements are expressed in terms of a sine series and the pressure fields inside the cavities are expressed with cosine series. The model solves for the coefficients of these sine and cosine terms. Kirchhoff’s thin elastic plate equations for two plates along with the continuity conditions at each plate and cavity connection are set as the governing equations. Orthogonality of the Fourier sine and cosine terms is implemented to solve the system of equations. Sound transmission loss is then calculated from the displacements of the radiating plate using the Rayleigh integral. Finally, the transmission losses are averaged over the incident angles. Similar model is available where panels although finite, are considered to be infinite. The transmission loss calculated using both the finite panel model and the infinite panel model agree with measurement data in the high frequency region. While in the low frequency region, the agreement is better with the finite panel model. Using this finite panel model the effect of finite dimensions of the panel is analysed. In addition, influence of the cavities to the overall sound transmission is described.
(1) University of Canterbury
ABSTRACT
Determining the influence of absorption laid directly on top of ceiling tiles within a suspended ceiling system was conducted with differing thicknesses of porous absorbers. The measurements were made in a commissioned CAC facility at the University of Canterbury, in New Zealand. This paper outlines the influence of different thicknesses of fibreglass absorption within the plenum on flanking sound above a common separating wall, through a plenum.
Maritime Division, Defence Science and Technology Group, Melbourne, Australia
ABSTRACT
The sound radiated from an underwater cylindrical enclosure with an internal noise source can be modelled analytically by combining a number of mathematical results. The scattered sound field due to a monopole source in the cylindrical volume provides the internal pressure loading on the cylinder walls; the response of the cylinder is calculated using this loading as the forcing term in a thin-shell theory formulation including external fluid loading; and the far-field radiated sound is then calculated using the cylindrical shell response as the input to an expression for this. Previous work applied this approach with an isotropic cylindrical shell and considered the effect of multiple noise sources and the incorporation of internal acoustic damping. This paper considers the extension of this model to allow for a cylindrical shell with longitudinal and/or radial stiffeners. Radiated sound calculated using the isotropic shell and variations on the stiffened shell is compared.
retired
ABSTRACT
When a cylindrical shell is excited by a steady axisymmetric force, axial and radial vibrations travel in the axial direction and undergo continued reflections at the two ends. The radial vibration radiates sound into the surrounding medium. To calculate the displacement of the radial vibration, four "thin shell theories" were examined: Membrane (M), Donnell-Mushtari (D), Flugge-Byrne-Lur'ye (F), and Epstein-Kennard (E). Of these, E makes the fewest approximations and is the most intricate of the twelve catalogued in Leissa's monograph "Vibration of shells". For a cylindrical shell of radius 3.25 m and wall thickness 40 mm (ratio 1.2%), spectra of radial displacement and far-field radiated sound were computed up to 10 kHz. The differences amongst the four theories are negligible over the whole band. When the wall thickness is increased to 200 mm (ratio 6.2%), the spectra are almost identical for frequencies up to around 2.5 kHz, but gradually diverge at higher frequencies. The results indicate that D and F require the wall thickness to not exceed around 10% of the vibration wavelength, whereas M and E allow that ratio to reach (and perhaps surpass) 30%.
(1) DST Group
ABSTRACT
The primary aim of a marine propeller is to propel a ship to a given speed. Other desirable objectives might then be to do this as quietly, and as efficiently as possible. This paper presents a general framework for mapping out the noise and efficiency space as we vary gross propeller design parameters such as diameter, blade area or pitch-diameter ratios. For propellers, thrust and efficiency are usually presented as functions of advance ratio, and may be estimated using computational methods, theoretical expressions or curves derived from experiments such as those for the Wageningen B-Series. In the test framework, we maintain the desired ship speed and the corresponding thrust as a fixed overarching requirement. This essentially determines an advance ratio for each potential propeller in a large pool of randomly generated designs. Propellers which cannot deliver the required thrust are discarded. We may insert other criteria such as cavitation onset or material stress conditions to further refine the pool of potential designs before generating a noise estimate for each remaining propeller. In this work, an empirical radiated propeller flow noise estimate is used as the noise criteria. It is demonstrated that, even in this highly idealised setting, efficiency and noise have a complicated trade-off space.
Centre for Marine Science and Technology, Curtin University, Bentley WA 6102, Australia
ABSTRACT
Wave propagation and attenuation in an infinite periodic structure is determined by the properties of equally spaced scatterers embedded in the structure. These properties are the complex forward and backward scattering coefficients and their dependence on the direction of the structure waves (SW) incident onto the scatterers. The theory for periodic structure waves (PSW) is constrained to be simultaneously consistent with the coupling of SW in adjacent "cells" between the scatterers, and conservation of energy where the scatterers generally absorb energy. Depending on the scattering parameters, PSW can be attenuated Bloch-Floquet waves (BFW), another extended PSW or up to two localized (non-propagating) "modes". The latter two non-BFW modes require by conservation of energy two phase correlated PSW coupled by scattering. It is shown that symmetry relationships must exist between the PSW properties for two different periodic structures that "mirror" each other by the forward scattering coefficient of one being equal to the backward scattering coefficient of the other. Hence deriving PSW results such as the SW reflectivity for one structure also provides corresponding results for its mirror structure.
(1) Australia Defence Science and Technology Group, Victoria, Australia
ABSTRACT
The radiation efficiency of a plate submerged in water is often used as a basis on which to represent the sound radiation from more complex underwater structures. The boundary conditions and stiffening ribs are known to have a significant influence on sound radiation from a plate for frequencies below the critical frequency. As it is difficult to measure the radiation efficiency in water, only limited experimental results for plates in air have been reported previously. A numerical and analytical investigation of the radiation efficiency of submerged plates is presented in this paper. The total radiation efficiency is developed from a numerical finite element model using ANSYS by averaging the efficiency due to three point force positions. The effect of boundary conditions and ribs on the total radiation efficiency is discussed in detail. The basic results are compared with those from a numerical boundary element model using SYSNOISE and two analytical engineering formulas. Excellent agreement is obtained between the two numerical methods. The analytical results agree less well with the numerical ones at low frequencies.
(1) School of Mechanical & Manufacturing Engineering, UNSW Australia, Sydney, Australia
ABSTRACT
The aeroacoustic noise produced by a wall mounted foil at a Reynolds number based on chord of Re_c = 1.1E6 and a Mach number of M=0.12 is predicted using a hybrid RANS-BEM technique. A steady-state Reynolds averaged Navier-Stokes (RANS) simulation provides hydrodynamic data of the flow around the foil, including information on the turbulence statistics. Using a model of the turbulence cross spectrum, statistical noise sources are obtained and then combined with a three-dimensional boundary element method (BEM) model of the airfoil to predict the far-field sound. The hydrodynamic and aeroacoustic results obtained using the hybrid RANS-BEM technique are in good agreement with experimental results.
ABSTRACT
In order to obtain a better understanding of the noise radiated by wind turbines, acoustic measurements were performed using a small-scale wind-turbine model. The wind-turbine, which operates at 900 RPM, is composed of 3 equally spaced NACA 0012 blades. The chord and length of the blades are 70 mm and 450 mm respectively. The pitch angle of the blades is set to either 0, 5, 10 or 15 degrees; the blades are not twisted, nor are they tapered. The wind-turbine was placed in 2 environments: an anechoic room at the University of Adelaide and a reverberant wind tunnel test section in the UNSW aerospace research laboratory. The purpose of this paper is to investigate the effects of the hard-walls of the wind tunnel on the acoustic measurements. The acoustic radiation of the rotating turbine was measured using a 64-microphone acoustic array and processed using a conventional beamforming (CBF) algorithm. The main source of sound for all cases is located at the blade tip. The blade tower interaction is clearly visible with an AoA of 0 degrees in the third octave [1600; 3200] Hz range. The effects of the reverberant environment are presented. While the main source is located at the same position in the two configurations, which means that acoustic measurement can be performed in the reverberant test section without any additional treatment, there are important differences between the measurements that will be discussed.
(1) School of Mechanical and Manufacturing Engineering, UNSW
ABSTRACT
This paper explores the noise produced by three-dimensional vortex flow at the tip of an airfoil. This noise source is an important component of the noise produced by aircraft high-lift systems. To investigate tip vortex formation noise, aeroacoustic measurements have been taken of a finite airfoil with flat ended tip in an anechoic wind tunnel at a range of flow speeds and angles of attack. Sound maps taken with a beamforming array are presented to show contributions of flow at the airfoil tip to overall airfoil noise production. Tip noise spectral data are also included to provide information about the nature of the noise source and scaling laws are developed of the noise generation process to collapse the noise data.
(1) Aurecon
ABSTRACT
Façade designs are becoming increasingly complex, resulting in an increased occurrence of a façade generating wind-induced noise which can be a nuisance for sensitive receivers. Despite this, wind-induced noise is often overlooked in the design of a façade. This paper highlights typical wind-induced noise mechanisms and typical methods used to assess and quantify the potential for a façade to generate noise. A novel technique is presented which was developed to assess the potential of a façade to generate noise. Application of this technique to a case study is discussed for the Adelaide Medical and Nursing Schools (AMNS) project, a new campus facility at the western end of North Terrace in Adelaide's CBD.
(1) School and Engineering, RMIT University, Melbourne, Australia (2) School of Electrical, Mechanical and Mechatronic System, University of Technology Sydney, Sydney, Australia (3) Faculty of Engineering and Information Technology, University of Technology Sydney, Sydney, Australia (4) Department of Water Resources and Environmental Engineering, Tamkang University, Taiwan
ABSTRACT
Wind noise generated by the intrinsic turbulence in the flow can affect the outdoor noise measurements. Various attempts have been made to investigate the wind noise generation mechanism. Wind noise spectra in anechoic wind tunnels can be divided into three frequency regions. In the low frequency region known as the energy-containing range, the wind noise spectrum does not change significantly with frequency. In contrast, in the middle frequency region (or inertial range) the decay rate of the wind noise spectrum curve follows the 7/3 power law, but in the high frequency region (or dissipation range) the decay rate of the wind noise spectrum curve is faster than the -7/3 power law. The boundaries of the -7/3 power law frequency range depend on the Reynolds number; however, no exact value is known according to current literature. This paper proposes a method for predicting the boundary values based on the energy cascade theory. Large eddy simulations of free jet were performed to validate the proposed method and the results were found to be in reasonable agreement with existing experiment measurements obtained in an anechoic wind tunnel. Additional simulations were also conducted with different inflow entrance sizes to further verify the predictions from the proposed method.