|Vol 36 No 2||
Low Frequency structural and acoustic responses of a submarine hull
Mauro Caresta, Nicole Kessissoglou and Yan Tso
The Robustness And Applicability Of Audio Source Separation From Single Mixtures
Md. Khademul Islam Molla, Keikichi Hirose and Nobuaki Minematsu
Hearing Protector Testing And Individual Variability
Are we assessing child care noise fairly?
Acoustics Australia Information
Vol. 36, No. 2 pp 47 - 52 (2008)
ABSTRACT: A model to describe the low frequency dynamic and acoustic responses of a submarine hull subject to a harmonic propeller shaft excitation is presented. The submarine is modelled as a fluid-loaded, ring stiffened cylindrical shell with internal bulkheads and end caps. The stiffeners are introduced using a smeared approach. The bulkheads are modelled as circular plates and the end closures as truncated conical shells. The propeller introduces a harmonic axial force that is transmitted to the hull through the shaft and results in excitation of the accordion modes only if the force is symmetrically distributed to the hull. Structural and acoustic responses for the axisymmetric breathing modes are presented in terms of frequency response functions of the axial and radial displacements and directivity patterns for the radiated sound pressure.
Vol. 36, No. 2 pp 55 - 59 (2008)
ABSTRACT: The separation of audio sources from their single mixture is a great challenge in signal processing research. Manysingle mixturesource separation techniques have been proposed in the past 20 years but unfortunately the results are not pleasing enough for practical applications. In this tutorial-review paper, single-channel audio source separation techniques are divided into three broad categories: separation by auditory scene analysis (ASA), training based separation and blind source separation (BSS). Each of the categories is briefly described to contrast their methodological differences.
This study focuses on the limitations and robustness under adverse acoustic environment of the seveal categories. We compare the success and usability of the different techniques in real world applications.
Vol. 36, No. 2 pp 60 - 62 (2008)
ABSTRACT: Consistency of test procedures is extremely important when certifying products for both safety purposes and Australian Standard requirements. The results presented in this study demonstrated that using the subject-fit methodology as specified in Australian New Zealand Standard AS/NZS 1270: 2002, Acoustics - Hearing protectors, hearing protector attenuation can be reliably measured to within 0.1 dB. A small learning effect was observed with a reduction in the standard deviation from 3.7 dB in the initial fit to 2.7 dB at the final presentation.
Vol. 36, No. 2 pg 63 (2008)
ABSTRACT: In recent years there has been a significant increase in the demand for child care, with many centres opening in 'normal' suburban streets, just a garden fence between the outdoor play area and the neighbour's garden. Some may feel that the sound of children playing is a happy sound; that childcare is part of life and should just be accepted. Others consider that child care can be a very profitable business and should be treated as any other commercial operation which has 'amenity' obligations to meet. Councils across NSW and the Land and Environment Court do not appear to have reached a clear decision on how to assess a child care centre.