Australian Acoustical Society ABN 28 000 712 658 A.C.N. 000 712 658

Vol 32 No 3

CONTENTS

December 2004

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ARTICLES

Visualisation/auralisation of sound fields for room acoustics
Tachibana H
Full Paper

Resonance theories of hearing - a history and a fresh approach
Bell A
Full Paper

Engineering methods of noise control for modular bridge expansion joints
Ancich E J and Brown S C
Full Paper

FORUM

Noise annoyance from seasonal industry in NSW
Scannell K
Full Paper

Recent Changes to the sound insulation provisions of the building code of Australia
Patterson M
Full Paper

INTERLUDE

Acoustics in the International Year of Physics
Fletcher N
Full Paper

Book Reviews
AAS Council
Letters
New Members
News
New Products
Meeting Reports
Future Meetings
Diary
Annual Index
Acoustics Australia Information
Australian Acoustical Society Information
Advertisers Index

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VISUALIZATION/AURALIZATION OF SOUND FIELDS FOR ROOM ACOUSTICS

Hideki Tachibana
Institute of Industrial Science, University of Tokyo
Komaba 4-6-1, Meguro-ku, Tokyo 153-8505, Japan
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Vol. 32, No. 3 pp 89-94 (2004)
ABSTRACT: The first step of architectural and acoustical design of a concert-hall/theatre is to choose the fundamental room shape. Secondarily, the shapes of walls and ceiling are designed so as to realize proper reflections and diffused (blended) sound field. As a basic study to investigate these points, 2-dimensional numerical analyses by the finite difference time domain (FDTD) method were performed for typical room shapes, rectangular, fan-shaped, elliptic, etc., with and without diffusive room boundaries. In this presentation, the differences of sound wave propagation and sound diffusivity in the rooms with different shapes and diffusion treatments are visualized by computer animation and the room impulse responses are compared by auralization technique. A new idea to simulate a sound field by combining the FDTD calculation and 4-channel reproduction system is also introduced.

RESONANCE THEORIES OF HEARING - A HISTORY AND A FRESH APPROACH

Andrew Bell
Research School of Biological Sciences
The Australian National University, Canberra, ACT 0200
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Vol. 32, No. 3 pp 95-100 (2004)
ABSTRACT: This paper provides an historical overview of how a powerful acoustical principle - sympathetic resonance - has been applied to our organ of hearing. It focuses on the principle's virtues, drawbacks, and varying fortunes. Why did Helmholtz's resonance theory of hearing in the 1850s fall from universal acceptance to near total disregard? What were the factors favouring travelling wave theories, most notably that of von Békésy in the mid 20th century? Post-Békésy, however, thinking on cochlear mechanics has been radically changed by findings that the cochlea is an active transducer, not a passive one as previously thought. As Kemp demonstrated in 1979, healthy cochleas are highly tuned and continuously emit narrow-band sound ... prompting the thought that something seems to be resonating. Maybe, then, it is worth re-examining resonance, even though travelling waves remain the centre-piece of the standard cochlear model. A fresh resonance formulation is described.

ENGINEERING METHODS OF NOISE CONTROL FOR MODULAR BRIDGE EXPANSION JOINTS

Eric J. Ancich,
Bridge Technology Section, Roads & Traffic Authority of NSW, P0 Box 558 Blacktown 2148.
Stephen C. Brown,
Richard fleggie Associates Pty Ltd, P0 Box 176 Lane Cove 1595.

Vol. 32, No. 3 pp 101-107 (2004)
ABSTRACT: Modular bridge expansion joints are widely used throughout the world for the provision of controlled pavement continuity during seismic, thermal expansion, contraction and long-term creep and shrinkage movements of bridge superstructures. It was known that an environmental noise nuisance occurred as motor vehicle wheels passed over the joint but the mechanism for the generation of the noise nuisance was not previously known. Noise abatement options were investigated before settling on a Helmholtz Absorber installation. The benefit is most obvious in the frequency range of 50 to 200 Hz. The noise reduction provided by the Helmholtz Absorber installation is of the order of 10 dBA.

FORUM

NOISE ANNOYANCE FROM SEASONAL INDUSTRY IN NSW

Ken Scannell
Noise and Sound Services
Spectrum House, 1 Elegans Avenue, St Ives NSW 2075

Vol. 32, No. 3 pp 109-110 (2004)

RECENT CHANGES TO THE SOUND INSULATION PROVISIONS OF THE BUILDING CODE OF AUSTRALIA

Matthew J. Patterson
Professional Services, Australian Building Codes Board, Canberra, Australia, www.abcb.gov.au

Vol. 32, No. 3 pp 111-116 (2004)
ABSTRACT: This paper discusses the recent changes to the Building Code of Australia (BCA) sound insulation requirements. It outlines the main drivers for the changes and looks at the process used by the Australian Building Codes Board to develop the measures. It also outlines the extent of the changes and the different options for demonstrating compliance with the BCA.

INTERLUDE

ACOUSTICS IN THE INTERNATIONAL YEAR OF PHYSICS

Neville Fletcher
Research School of Physical Sciences
Australian National University, Canberra 0200

Vol. 32, No. 3 pp 117-118 (2004)

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