| Vol 32 No 3 | CONTENTS |
December 2004 |
Visualisation/auralisation of sound fields for room acoustics
Tachibana H
Resonance theories of hearing - a history and a fresh approach
Bell A
Engineering methods of noise control for modular bridge expansion joints
Ancich E J and Brown S C
Noise annoyance from seasonal industry in NSW
Scannell K
Recent Changes to the sound insulation provisions of the building code of Australia
Patterson M
Acoustics in the International Year of Physics
Fletcher N
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
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.
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.
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.
Vol. 32, No. 3 pp 109-110 (2004)
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.
Vol. 32, No. 3 pp 117-118 (2004)