Home Journal
E-mail Print
Acoustics Australia  Logo (3032 bytes)

Vol 41 No 1

CONTENTS

April 2013


LETTERS

Response to: S. Cooper, ?Wind farm noise - an ethical dilemma for the Australian Acoustical Society??,? Acoustics Australia 40(2), 139-142 (2012)
Ray Tumney
PDF Full Paper

Wind Farm Noise - The Debate
Graeme E. Harding
PDF Full Paper

ARTICLES

International regulation of underwater noise
Christine Erbe
PDF Full Paper

Investigation of underwater acoustic multi-path Doppler and delay spreading in a shallow
marine environment

Michael Caley and Alec Duncan
PDF Full Paper

A semi-analytical model for non-Mach peak pressure of underwater acoustic pulses from
offshore pile driving
Marshall V. Hall
PDF Full Paper

Methods to classify or group large sets of similar underwater signals
L. J. Hamilton
PDF Full Paper

The sounds of fish off Cape Naturaliste, Western Australia
Miles Parsons, Robert McCauley and Frank Thomas
PDF Full Paper

Seabed multi-beam backscatter mapping of the Australian continental margin
Rudy J. Kloser and Gordon Keith
PDF Full Paper

An analysis of glider data as an input to a sonar range dependent acoustic performance
prediction model

Janice Sendt
PDF Full Paper

Modelling acoustic transmission loss due to sea ice cover
Polly Alexander, Alec Duncan, Neil Bose and Daniel Smith
PDF Full Paper

A study of the behavioural response of whales to the noise of seismic air guns: Design,
methods and progress

Douglas H. Cato, Michael J. Noad, Rebecca A. Dunlop, Robert D. McCauley, Nicholas J. Gales, Chandra P. Salgado Kent, Hendrik Kniest, David Paton, K. Curt S. Jenner, John Noad, Amos L. Maggi, Iain M. Parnum and Alec J. Duncan
PDF Full Paper

Propagation of wideband signals in shallow water in the presence of meso-scale horizontal
stratification

Boris Katsnelson, Andrey Malykhin and Alexandr Tckhoidze
PDF Full Paper

Quantifying the acoustic packing density of fish schools with a multi-beam sonar
Miles J.G. Parsons, Iain M. Parnum and Robert D. McCauley
PDF Full Paper

TECHNICAL NOTES

Underwater passive acoustic monitoring & noise impacts on marine fauna?A workshop report
Christine Erbe.
PDF Full Paper

Book Reviews
News
Grants & Awards
New Products
Divisional News
Future Conference
Obituary
Diary
Sustaining Members
Advertisers Index


International regulation of underwater noise

Christine Erbe
Centre for Marine Science and Technology, Curtin University, Perth 6845, Western Australia
This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Vol. 41, No. 1 pp 12 - 19 (2013)
ABSTRACT: Underwater noise is a by-product of marine industrial operations, that plays an increasing role in environmental impact assessments. It can have a variety of temporary to chronic bioacoustic impacts on marine fauna, such as behaviour modification, changes in habitat usage or migration, communication masking, and auditory and non-auditory physiological impacts. There are still lots of unknowns. Audiograms (curves of hearing sensitivity) have only been measured of few individuals of about 20 marine mammal species, and even fewer individuals and species of other marine genera. No audiograms exist for sperm whales or baleen whales. Behavioural responses likely depend on prior experience (habituation versus sensitisation), age, gender, health, context, current behavioural state etc., but we don?t understand the details or mechanisms. Data on hearing loss and acoustic trauma is even scarcer. Finally, what is the biological significance of individual acoustic impacts? Environmental agencies and regulators struggle for data to support environmental management. Research on the impacts of underwater noise is being undertaken around the globe, but there is a substantial delay in publication and science transfer. In the face of uncertainty, what is being done? This article aims to provide a brief overview of underwater noise regulation in Australia and overseas. Regulations vary from country to country. Some jurisdictions use specific do-not-exceed thresholds, which are very broadly applied across differing species and environments, and sound sources. Others use more conceptual requirements such as ?minimising impact to acceptable levels?, yet what this means has to be defined and demonstrated by each proponent for their specific situation (i.e., operation, environment and organisms). Furthermore, in many situations, multiple differing Acts and policies apply.

Investigation of underwater acoustic multi-path Doppler and delay spreading in a shallow
marine environment

Michael Caley and Alec Duncan
Curtin University, Department of Imaging and Applied Physics, Centre for Marine Science and Technology, Perth, Australia
This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Vol. 41, No. 1 pp 20 - 28 (2013)

ABSTRACT: Doppler frequency spreading and arrival delay spreading of underwater acoustic communication signals under the influence of surface waves and transmitter-receiver motion were investigated in a channel probing experiment conducted primarily with binary pseudo-noise (PN) sequences ranging from 21ms to 1.4s duration. Testing was conducted in a 13.5m deep environment at transmission distances ranging from 44m to 1007m. The channel Doppler response was investigated both by time-domain Doppler search of the transmit-receive correlation for successive repeats of a 1.4s probe sequence, and by Fourier analysis of the channel impulse response history from a repeated 21ms probe sequence (i.e. Spreading Function). The bounds of Doppler shift imparted by relative transmitter/receiver motion and surface wave motion to idealised sound-ray transmission paths has been compared with experimental Doppler indicated by the Spreading Function. The coherence of the experimental channel response was also examined for different propagation ranges and at different delayed arrivals of the experimental signals.

Inference of geoacoustic model parameters from acoustic field data

N. Ross Chapman
School of Earth and Ocean Sciences, University of Victoria, Victoria, BC V8P5C2, Canada
This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Vol. 41, No. 1 pp 29 - 41 (2013)
ABSTRACT: The interaction of sound with the ocean bottom has a significant impact on the acoustic field in the ocean, especially in shallow water. Over the past several decades, there has been a high level of research activity in ocean acoustics to understand the physics of sound propagation in the ocean bottom. This work has led to the general practice of using geoacoustic models, - profiles of the sound speed, attenuation, and density of ocean bottom materials ? to describe the bottom. Much of the research was focused on developing inversion methods to determine geoacoustic model parameter values from the information about the model contained in measurements of the acoustic field ? or quantities that can be derived from the field ? in the water. This paper reviews the stages in the development of geoacoustic inversion as a statistical inference process to estimate geoacoustic model parameter values and their associated uncertainties. Applications of linear inversions and non-linear inversions based on matched field processing are presented for analysis of their performance in estimating realistic geoacoustic models. The paper concludes by pointing out limitations in the present day inversion techniques that can severely limit performance, and discusses some new approaches that provide robust performance without compromising the accuracy of the estimated model parameters.

A semi-analytical model for non-Mach peak pressure of underwater acoustic pulses from
offshore pile driving

Marshall V. Hall
Moya Crescent, Kingsgrove NSW 2208, Australia
This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Vol. 41, No. 1 pp 42 - 51 (2013)
ABSTRACT: The equations of motion for the axial and radial displacements in a hammered semi-infinite pile comprise a system of coupled partial differential equations which are solved by taking their Fourier Transforms. The impact generates a pulse of axial and radial vibrations (a bulge) that disperses slightly as it travels down the pile. The damping rate is high at frequencies close to the radial resonance frequencies of the pile. After the bulge arrives at a given depth, the axial displacement increases with time to an asymptote, whereas the radial displacement rapidly rises to a peak and then decays to zero. Although the bulge constitutes a moving sound source, the radiated peak pressure is computed as if it were stationary at a number of depths. The ratio of pressure to fluid particle velocity at the pile wall is obtained by assuming the pile to be in a homogeneous medium. The spectrum of radial displacement, which is subject to radiation loading, is expressed as a closed-form algorithm in terms of the hammer impact velocity, the radius and wall thickness of the pile, and the Poisson ratio, longitudinal sound-speed, and density of the pile material. The radial displacement algorithm is linked to two simple models for sound radiation from a cylinder: near-field from depth-independent vibration, and far-field from depth-dependent vibration. These models are applied to a published case for which radiated peak pressures were measured and computed at a fixed range from a steel pile, using a Finite Element Model. The near-field/ depth-independent model overestimates the peak pressure, since it assumes that the cylinder is of infinite length. The far-field/ depth-dependent model underestimates the observed peak pressure. If a sound source moves supersonically perpendicular to a sound propagation path then coherent multipaths arrive quasi-simultaneously (Mach waves). The first model over-estimates the Mach wave pressure from a finite cylinder, while the second model neglects Mach waves altogether. A non-rigorous method for estimating the Mach wave pressure is described.

Methods to classify or group large sets of similar underwater signals

L. J. Hamilton
Defence Science & Technology Organisation (DSTO), 13 Garden St, Eveleigh, NSW 2015
This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Vol. 41, No. 1 pp 52 - 57 (2013)
ABSTRACT: Three methods of classifying large sets of acoustic signals are briefly discussed. The purpose of the discussion is to broadcast the existence and summary details of the methods to a wider audience. Large implies that hundreds of signals to several tens of thousands of signals may be detected. The signals of interest are broadly Gaussian, Rayleigh, or sinusoidal in shape, and of finite duration, such as seabed echoes and beaked whale chirps. The classification methods are (1) feature analysis, (2) direct statistical clustering of signals treated as single-valued curves, and (3) matched filtering with use of normalisations and kurtosis of the cross-correlation function output of the matched filter. Method (1) has been used for many years in several fields of science. It is suitable for many applications, but classifies on proxies, not the actual signals, which may lead to loss or distortion of information. Method (2) is a post processing operation suitable for signals with well defined signal to noise ratio which can be well aligned in time. Although simple in concept, it is a recent innovation, as it was apparently not previously realised that it could be done. A suitable clustering algorithm can classify signals into groups or sets where each set has a different average shape from the other sets, and can also classify signals forming quasi-continuums, such as those which can be viewed as morphing from one shape to another. Method (3) is suitable for detection and classification of stereotypical signals (those with strongly repeating waveform or signal shape), including weak signals in noisy backgrounds. In the usual application of matched filtering, classification is made solely on the un-normalised amplitude of the cross-correlation function. A novel extension of method (3) is to provide a confidence estimate for the classification through the kurtosis of the normalised autocorrelation function. The kurtosis is observed to be related to the degree of signal distortion or malformation relative to the template signal. When incoming signals of the same type vary in energy and degree of distortion or malformation, this scheme greatly outperforms standard matched filtering.

The sounds of fish off Cape Naturaliste, Western Australia

Miles Parsons, Robert McCauley and Frank Thomas
Centre for Marine Science and Technology, Curtin University, WA 6845, Australia
This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Vol. 41, No. 1 pp 58 - 64 (2013)

ABSTRACT: Fish calls and choruses contribute considerable energy to the underwater soundscapes of Western Australia's waters. There are many fish species of social and economic importance which could be the source of these sounds. For example, the Western Australian dhufish (Glaucosoma hebraicum), which is endemic to the coast, has been shown to produce sound when captured. To investigate how much this species contributes to ambient noise levels, loggers were deployed between December, 2011 and February, 2012 at numerous locations around Cape Naturaliste in Western Australia, where some of the largest numbers of G. hebraicum are reported. Recordings taken near the site of the HMAS Swan wreck between 2009 and 2010 were also examined. Five fish choruses have been described centred at approximately 0.5, 1, 2 and >2 kHz (two choruses at >2 kHz). Many individual fish calls were detected at various locations around the Cape, particularly in the frequency ranges between 100 and 900 Hz. The acoustic characteristics of these calls are described, as well as the contribution of fish calls and choruses to the local soundscapes. The calls most similar to the previously reported G. hebraicum calls have been identified.

Seabed multi-beam backscatter mapping of the Australian continental margin

Rudy J. Kloser and Gordon Keith
CSIRO Wealth from Oceans Flagship, Marine and Atmospheric Research, GPO Box 1538, Hobart, Tasmania 7001, Australia
This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Vol. 41, No. 1 pp 65 - 72 (2013)
ABSTRACT: A multi-beam sonar (MBS) has been used to map Australia?s continental margin seabed from the marine national facility vessel Southern Surveyor on opportunistic transit and research voyages since 2004 with 0.35 M km2 mapped. The MBS data are used to infer key ecological features based on bathymetry (e.g. seamounts, canyons, terraces, banks and deep reefs) and backscatter data for ecological hard (consolidated, e.g. rock for attachment of fauna) and soft (unconsolidated, e.g. mud for burrowing fauna) substrate. Seabed consolidation inference is consistent with a seabed scattering model. To consistently infer ecological significant hard and soft substrate from the backscatter data requires minimisation of errors due to changing absorption (~2 dB) with temperature and depth, calibration drift, changes in pulse length and estimates of area insonified due to seabed slope (<8 dB). Area insonified corrections were required for both across and along-ship slopes. Highest corrections were needed for along-ship slopes in canyon regions and large incidence angles (>60?). A data collection and processing framework is described that works towards a national backscatter mapping program for environmental seabed mapping. Data collected and automated processing for depth, sound absorption and area insonified at level 2 of a possible 5 level data processing hierarchy is available for viewing at http://www.marine.csiro.au/geoserver.

An analysis of glider data as an input to a sonar range dependent acoustic performance
prediction mode

Janice Sendt
Thales Underwater Systems, Thales Australia, 274 Victoria Road, Rydalmere NSW 2116 Australia
This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Vol. 41, No. 1 pp 73 - 78 (2013)
ABSTRACT: This paper describes an initial assessment of the role of glider data as an input into a sonar nowcast acoustic detection range prediction model. It includes an analysis of the temporal and spatial variability of the water column data measured by a glider in shallow Australian waters. The area covered by the data includes a region where there is a known persistent frontal feature. The glider data verified that a persistent front was present in the data.

Modelling acoustic transmission loss due to sea ice cover

Polly Alexander1,2 , Alec Duncan3 , Neil Bose1 and Daniel Smith2
1 Australian Maritime College, University of Tasmania, Maritime Way, Launceston, TAS 7248, Australia
2 Intelligent Sensing and Systems Laboratory, CSIRO ICT Centre, Hobart, TAS, 7000, Australia
3 CMST Curtin University, Kent Street, Bentley, Perth, WA, 6102, Australia
This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Vol. 41, No. 1 pp 79 - 87 (2013)
ABSTRACT:The propagation of underwater acoustic signals in polar regions is dominated by an upward refracting sound speed environment and the presence of a dynamic highly variable ice canopy. This paper provides an overview of the acoustic properties of sea ice and assesses the influence of ice canopy and water column properties on acoustic transmission loss for propagation within 20 km of a sound source at 20 m depth. The influence of the ice canopy is assessed first as a perfectly flat surface, and then as a statistically rough surface. A Monte Carlo method is used for the inclusion of ice deformation and roughness. This involves the creation of sets of synthetic ice profiles based on a given sea ice thickness distribution, followed by statistical methods for combining the output of individually evaluated ice realisations. The experimental situation being considered in the framing of this problem is that of an Autonomous Underwater Vehicle (AUV) operating within 50 m of the surface. This scenario is associated with a frequency band of interest of 9-12 kHz and a horizontal range of interest up to 20 km. The situation has been evaluated for a set of typical ice statistics using Ray and Beam acoustic propagation techniques. The sound speed profile (based on real data) results in a strong defocussing of direct path signals at ranges from 9-20 km and depths shallower than 50 m. This reduction in the signal strength of the direct path creates areas where the influence of surface reflected paths becomes significant. The inclusion of a perfectly flat ice layer reduces the transmission loss between 9-20 km by 15-50 dB. When the ice layer is included as a rough surface layer the results show a boost to signal strength of up to 8 dB in the small areas of maximum defocussing. Sea ice is a strongly time and space varying sea surface and exists in areas where defocussing of the direct path due to the sound speed profile reduces the range of direct path dominated transmission. This work presents methods for including a statistically relevant rough surface through a technique for generation of sets of surfaces based on ice deformation statistics. It outlines methods for including ice in acoustic modelling tools and demonstrates the influence of one set of ice statistics on transmission loss.

A study of the behavioural response of whales to the noise of seismic air guns: Design,
methods and progress

Douglas H. Cato1, Michael J. Noad2, Rebecca A. Dunlop2, Robert D. McCauley3, Nicholas J. Gales5, Chandra P. Salgado Kent3, Hendrik Kniest5, David Paton6, K. Curt S. Jenner7, John Noad2, Amos L. Maggi3, Iain M. Parnum3 and Alec J. Duncan3
1Maritime Operations Division, Defence Science and Technology Organisation, Sydney, NSW and University of Sydney, NSW
2Cetacean Ecology and Acoustics Laboratory, School of Veterinary Science, University of Queensland, Gatton, QLD
3Centre for Marine Science and Technology, Curtin University of Technology, Perth, WA
4Australian Marine Mammal Centre, Australian Antarctic Division, Kingston, TAS
5University of Newcastle, Newcastle, NSW
6Blue Planet Marine, Canberra, ACT
7Centre for Whale Research, WA

Vol. 41, No. 1 pp 88 - 97 (2013)
ABSTRACT: The concern about the effects of the noise of human activities on marine mammals, particularly whales, has led to a substantial amount of research but there is still much that is not understood, particularly in terms of the behavioural responses to noise and the longer term biological consequences of these responses. There are many challenges in conducting experiments that adequately assess behavioural reactions of whales to noise. These include the need to obtain an adequate sample size with the necessary controls and to measure the range of variables likely to affect the observed response. Analysis is also complex. Well designed experiments are complex and logistically difficult, and thus expensive. This paper discusses the challenges involved and how these are being met in a major series of experiments in Australian waters on the response of humpback whales to the noise of seismic airgun arrays. The project is known as BRAHSS (Behavioural Response of Australian Humpback whales to Seismic Surveys) and aims to provide the information that will allow seismic surveys to be conducted efficiently with minimal impact on whales. It also includes a study of the response to ramp-up in sound level which is widely used at the start of operations, but for which there is little information to show that it is effective. BRAHSS also aims to infer the longer term biological significance of the responses from the results and the knowledge of normal behaviour. The results are expected to have relevance to other sources and species.

Propagation of wideband signals in shallow water in the presence of meso-scale horizontal
stratification

Boris Katsnelson1, Andrey Malykhin2 and Alexandr Tckhoidze1
1School of Marine Sciences, University of Haifa, 31905, Israel
2Physics Department of Voronezh University, Voronezh, 394006, Russia
This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Vol. 41, No. 1 pp 98 - 106 (2013)
ABSTRACT: In the paper examples of an oceanic waveguide with parameters varying in the horizontal plane are considered: an area of coastal wedge, (slopes and canyons), an area of varying water layer properties - in the presence of nonlinear internal waves and a temperature front. In these cases there is significant horizontal refraction or redistribution of the sound field in the horizontal plane. Due to waveguide dispersion (dependence of modal propagation constants on frequency) the refraction index in the horizontal plane depends on frequency also, and it is possible to observe different spatial and temporal variations of the sound signal similar to those in a two dimensional medium with frequency and spatial dispersion. This can be manifested as a non-stationary interference pattern, arrival time variations, and/or variations of spectra. These effects can be used to solve different inverse problems especially by using horizontal and vertical line arrays.

Quantifying the acoustic packing density of fish schools with a multi-beam sonar

Miles J.G. Parsons, Iain M. Parnum and Robert D. McCauley
Centre for Marine Science and Technology, Curtin University, WA 6845, Australia

Vol. 41, No. 1 pp 107 - 112 (2013)
ABSTRACT: Multi-beam (swath) sonar systems provide the capability to ensonify an entire aggregation of fish in a single pass. However, estimation of abundance and discrimination between species via the use of target strength are considerably more complex than using traditional echosounders, because they ensonify targets at a much wider range of incidence angles. The beam pattern and along beam resolution of multi-beam swaths can produce individual sample volumes that are of similar magnitude to an individual fish (particularly for large fish, say >1m in length). If individual fish can be resolved, (either as a single fish within a sample, or as multiple contiguous samples that delineate a single fish), and if one assumes that this situation applies to the whole school, acoustic packing density can be determined by dividing the volume of the school by the number of detected acoustic targets. This estimate is proportional to the actual packing density of the fish, defined as the number of fish per unit volume of water. Acoustic backscatter of fish from a number of schools comprising different species were collected off Perth, in 2005 and 2007, using a Reson Seabat 8125 and 7125 respectively. Nearest neighbour distances of between 1 and 3 body lengths were observed and packing density of acoustic targets showed distinct variation between some species. However, schools of the same species also displayed different acoustic packing densities at different stages of their growth and development. Such differences were more difficult to observe in schools of fewer fish because the variations in packing density had less impact on the overall volume of the smaller schools associated with fewer fish. Therefore discrimination between species was only deemed possible when surveying two species of different sized fish at the same time. Video ground truth data is recommended to confirm species composition whatever the type of school observed.

Underwater passive acoustic monitoring & noise impacts on marine fauna?A workshop report

Christine Erbe
Centre for Marine Science and Technology, Curtin University, GPO Box U1987, Perth 6845, Western Australia
This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Vol. 41, No. 1 pp 113 - 119 (2013)
ABSTRACT: The marine ecosystem is being increasingly subjected to underwater noise from industrial operations. Our ability to monitor the marine soundscape using passive acoustic technology is important to determine the potential impacts of anthropogenic sound. The objectives of this workshop were to define our current capabilities with regard to passive acoustic monitoring (PAM); to define our current state of knowledge of the marine soundscape, and of underwater noise in particular, and of noise impacts; to identify the needs and concerns of the various stakeholders; and to determine future research and development needs. The workshop was held in Fremantle, Western Australia, on 21 November 2012, the day before the Australian Acoustical Society?s annual conference. Three tutorial sessions were presented by leading researchers in the field on underwater acoustic terminology, metrics, the basics of sound propagation, noise modelling and prediction, the marine soundscape (physical ambient, anthropogenic and biological sources), sound recording technology and methods, noise impacts on marine fauna, mitigation and environmental management. Tutorials were followed by rapid-fire presentations of current research associated with the themes of passive acoustic monitoring and noise impact. Discussions pursued on the presented topics, with emphasis on stakeholder needs, prevailing problems, knowledge gaps, potential solutions and future initiatives. The workshop was attended by over 70 participants from within Australia and abroad, hosting a diverse range of expertise and representing the various stakeholders in the marine environment: the offshore oil and gas industry, consulting industry, fishing industry, defence, government (environmental officers, regulators, fisheries officers), environmental groups and academia. The outcomes of the workshop were:

  • An appreciation of PAM for monitoring of marine fauna, for ecological studies, for measurements of anthropogenic noise, for studying noise impacts and for mitigation monitoring;
  • A demonstration of the effectiveness of PAM for presence and abundance monitoring (with more acoustic detections than visual in certain circumstances);
  • An understanding of the limitations of PAM (to vocalising animals) and the potential of combining PAM with visual observations and possibly active acoustic imaging to increase detection probability;
  • An appreciation of the differences between regulatory approaches in different jurisdictions;
  • The identification of the need to monitor (and address noise impacts on) entire ecosystems including less iconic (=non-mammalian) species;
  • The identification of knowledge gaps with regards to unidentified sounds in marine soundscapes, natural variability in soundscapes with space and time necessitating long-term baseline recording, noise impacts on the vast majority of marine species, anthropogenic source signatures and sound transmission.
 

Newsflash

PROPOSED INTERNATIONAL YEAR OF SOUND 2019

Let's make 2019 the International Year of Sound!

Click here to see draft prospectus. Suggestions for major activities that would be truly international to strengthen the application are welcomed.

 

ACOUSTICS 2017

Perth, Western Australia 19-22 November 2017