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Vol 38 No 3

CONTENTS

December 2010


ARTICLES

The statistical distribution of expected noise level output from commonly available personal stereo players
W. Williams and J. Purnell
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The acoustic performance of novel noise barrier profiles measured at the roadside
Jeffrey Parnell, Stephen Samuels and Con Tsitsos
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A review of trailing edge noise generated by airfoils at low to moderate Reynolds number
E.J.G. Arcondoulis, C.J. Doolan, A.C. Zander and L.A. Brooks
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Use of CFD to calculate the dynamic resistive end correction for microperforated materials
J. Stuart Bolton and Nicholas Kim
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Numerical prediction of the transmission loss of leaks in trimmed panels
Israel Pereira, Marcus Guettler and Sascha Merz
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A comparison of techniques for ranging close-proximity mulloway (Argyrosomus japonicus) calls with a single hydrophone
Miles J.G. Parsons, Robert D. McCauley, Michael C. Mackie and Alec J. Duncan
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An automated web technique for a large-scale study of perceived vowels in regional varieties of English
Ahmed Ghonim, John Smith and Joe Wolfe
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TECHNICAL NOTES

Music to my ears campaign: preventing a deaf generation
Nick Parkyn
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Creating restaurant vibrancy without noise
Michael Haywood
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The statistical distribution of expected noise level output from commonly available personal stereo players

W. Williams1 and J. Purnell2
1National Acoustic Laboratories, Chatswood, NSW 2067
2Chatswood High School, Chatswood, NSW 2067

Vol. 38, No. 3 pp 119 -122? (2010)
ABSTRACT: This work presents a summary of the equivalent at-ear sound levels that can be expected to be experienced by users of personal stereo players. Estimates of inter-device and inter-earphone variability are also provided along with variations in performance and maximum output levels. This variation in acoustic output levels may mean that attempts by users to control noise exposure by monitoring the electrical output may not be as simple as first envisaged. A simple method is provided for the estimation of PSP output level with respect to the volume setting.

The acoustic performance of novel noise barrier profiles measured at the roadside

Jeffrey Parnell1, Stephen Samuels2 and Con Tsitsos3
1Noise Specialist, NSW Department of Planning, Sydney, Australia
2Visiting Research Fellow, University of NSW, Sydney, Australia. Director, TEF Consulting, Sydney, Australia
3Environmental Officer ? Noise, NSW Roads and Traffic Authority, Sydney, Australia

Vol. 38, No. 3 pp 123 -128 (2010)
ABSTRACT: As part of continuing investigation into noise barrier optimisation, a research and development study to conduct insitu empirical testing of several full size prototype barrier designs was funded by the NSW State Government. Of particular interest to this study was a design known as a random edge profile barrier. Literature research had found that there was a body of evidence indicating that a barrier with an edge irregularity can cause a substantial degradation of the diffracted signal. It is generally accepted that an increase in insertion loss occurs because the jagged edge causes a reduction in coherence of the diffracted signal being transmitted to the shadow zone as compared to a conventional straight edge barrier [1-3]. It has been suggested that the mechanism for this is that the jagged geometry on the top of a barrier alters the sound pressure level in the shadow zone by causing the region of the barrier nearest the receiver to admit multiple paths with variable phase [4]. The direct waves from the diffracting edges of the barrier and waves subsequently reflected from the ground plane are superimposed at the receiver causing constructive or destructive interference at the receiver. The present study followed a methodology that included construction of an 80m long by 2.4m high barrier that served as the base for an additional conventional top as well as a random profile and T-top novel cap. Empirical data collected showed that for the receiver locations investigated, a random edge barrier will out-perform a conventional barrier of the same nominal height for most frequencies associated with broadband tyre/road noise. A T-top barrier was found to perform better than a conventional barrier of similar height for most frequencies whilst a conventional barrier offered the most practical solution for attenuation of low frequency noise.

A review of trailing edge noise generated by airfoils at low to moderate Reynolds number

E.J.G. Arcondoulis, C.J. Doolan, A.C. Zander and L.A. Brooks
School of Mechanical Engineering, University of Adelaide, SA 5005


Vol. 38, No. 3 pp 129 -133 (2010)
ABSTRACT:? This paper contains a detailed literature review of research findings regarding the cause of flow-induced noise created by airfoils operating at low to moderate Reynolds numbers. There are many important engineering applications that operate at these conditions. More investigation is required to understand why airfoils in this range of Reynolds numbers produce high levels of tonal noise. As discussed in this paper, there are still many uncertainties surrounding the nature of the source.

Use of CFD to calculate the dynamic resistive end correction for microperforated materials

?J. Stuart Bolton and Nicholas Kim
Ray W. Herrick Laboratories, Purdue University, West Lafayette In, USA

Vol. 38, No. 3 pp 134 -139 (2010)
ABSTRACT:? The classical Maa theory for microperforated materials was initially formulated for constant diameter, cylindrical holes. Since then, a number of ad hoc corrections have been suggested to account for different hole shapes: in particular, rounding of the aperture. Here it is shown that the resistance and reactance of small apertures may be calculated using relatively simple CFD models in which a single hole is modelled. The fluid is assumed to be viscous but incompressible, and the geometry is assumed to be axisymmetric. It will be shown that this approach essentially reproduces the classical theory of Maa for circular, sharp-edged apertures. However, it will also be shown that the resistive end correction, in particular, exhibits a clear dependence on frequency and geometrical parameters that is neglected in conventional microperforated material models.

Numerical prediction of the transmission loss of leaks in trimmed panels

Israel Pereira1, Marcus Guettler2 and Sascha Merz3
1Universidade Federal de Santa Catarina, Brazil
2Technische Universitaet Dresden, Germany
3ESI US R&D San Diego, USA

Vol. 38, No. 3 pp 140 -144 (2010)
ABSTRACT:? Small holes and pass-throughs can often have a significant impact on the transmission loss of trimmed panels, particularly at mid and high frequencies. The effect of such ?leaks? can be included in modelling methods such as Statistical Energy Analysis (SEA) by using various analytical leak models. Such models typically assume a simple cross-sectional geometry in order to calculate the leak TL. However, for more complex configurations, for example, where a pass-through only penetrates certain layers of a multi-layer noise control treatment applied to the panel, a more detailed model is required in order to determine the TL of the leak. In this paper, Foam Finite Elements have been used to create such local models in order to predict the TL of partially trimmed pass-throughs. This local TL can then be used to update a system level SEA model. In addition, the paper demonstrates the widely known result that the TL of a simple hole does not depend on its cross-sectional shape but only its cross-sectional area and length. Results are presented for a number of examples.

A comparison of techniques for ranging close-proximity mulloway (Argyrosomus japonicus) calls with a single hydrophone

Miles J.G. Parsons1, Robert D. McCauley1, Michael C. Mackie2 and Alec J. Duncan1
1Centre for Marine Science and Technology, Curtin University, GPO Box U1987, Perth, WA 6845, Australia
2Department of Fisheries, Government of Western Australia, PO Box 20, North Beach, WA 6020, Australia

Vol. 38, No. 3 pp 144 -150 (2010)
ABSTRACT:? The accurate ranging of sounds produced by fish can provide valuable information on species ecology, and fish calls are being increasingly used to delineate and evaluate spawning grounds. In 2008, a single hydrophone was deployed on the riverbed of the Swan River, Western Australia, to assess the most effective technique for ranging mulloway (Argyrosomus japonicus) calls. During this experiment, the ranges of a calling mulloway were calculated using four techniques. These techniques involved comparing the characteristics of the direct and surface -reflected paths using: 1) arrival-time difference; 2) the pressure-amplitude ratios; 3) pulse sound-pressure-level ratios and; 4) a combination of techniques 1) and 2). Technique 1 proved the most consistent ranging technique, with accuracy limited by wave-motion-induced variation in water depth. However, a combination of the tested techniques is recommended when ranging fish.

An automated web technique for a large-scale study of perceived vowels in regional varieties of English

Ahmed Ghonim, John Smith and Joe Wolfe
School of Physics, The University of New South Wales, Sydney NSW 2052
This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Vol. 38, No. 3 pp 151 -155 (2010)
ABSTRACT: Because vowels in English are largely distinguished by the frequencies of their first two formants (F1, F2), the division of the (F2, F1) plane is an important and quantifiable component of accents. We report results of a web-based study into some of the many accents of English. Participants identified the vowel in h[vowel]d words produced by synthesis from a large set of possible values of F1, F2 and F3, using two different fundamental frequencies and two different durations. Compared to analysing spoken utterances, this approach has a number of obvious disadvantages, which we discuss. It has the significant advantages, however, of low cost, large scale and wide-ranging international participation. It is then possible to use the same experimental protocol to characterise the (perceptual) vowel plane of a substantial number of subjects and accents, thus allowing simple comparisons. From the large data base thus acquired, we present four examples of vowel maps for different Anglophone countries and regions therein. Knowledge of local variations in the perceptual (F2, F1) map, and the way in which these depend on fundamental frequency f0, is not only of phonetic interest, but may be useful to those who use synthetic speech in automated communication systems.

 

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