|Vol 32 No 3||
Visualisation/auralisation of sound fields for room acoustics
Resonance theories of hearing - a history and a fresh approach
Engineering methods of noise control for modular bridge expansion joints
Ancich E J and Brown S C
Noise annoyance from seasonal industry in NSW
Recent Changes to the sound insulation provisions of the building code of Australia
Acoustics in the International Year of Physics
Acoustics Australia Information
Australian Acoustical Society Information
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)