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Vol 29 No 2

CONTENTS

August 2001


ARTICLES

Virtual Sensors in Active Noise Control
C.D. Kestell, C.H. Hansen & B.S. Cazzolato
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Acoustic Daylight - using ambient noise to see underwater
M.L. Readhead
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An approach to estimation of underwater hearing thresholds and noise exposure limits
K. Kuramoto, K. Oimatsu, S. Kuwahara & S. Yamaguchi
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Recent developments in the design and performance of road traffic noise barriers
S. Samuels & E. Ancich
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VIRTUAL SENSORS IN ACTIVE NOISE CONTROL

Colin D, Kestell, Colin H, Hansen and Ben S, Cazzolato
Department of Mechanical Engineering,
University of Adelaide SA 5005, Australia

Vol. 29, No. 2 pp 57-61 (2001)
ABSTRACT: Traditional active noise control systems achieve the greatest noise reduction at the locations of the error sensor(s). In many cases it is desirable to be able to achieve the maximum noise reduction remote from an error sensor. One way of doing this is to measure the transfer function between the desired location of maximum reduction and the error sensor and incorporate it in the control algorithm. The disadvantage of this method is that it is not robust to changes in the acoustic environment. Another method relies on using two or more microphones to estimate the sound level at a remote location using forward prediction. This method results in a lower performance but it can be adapted to changes in the acoustic environment as well as to changes in the location of the desired pressure minimum. This paper will report on a study that compares the relative merits of various forward prediction method in various situations. These commence with a free field environment (to introduce the concept) and then progress to a more practical application of an aircraft cabin. Single and multiple control sources will be considered as will sound pressure sensing and energy density sensing.

ACOUSTIC DAYLIGHT -- USING AMBIENT NOISE TO SEE UNDERWATER

Mark L. Readhead
Maritime Operations Division, Defence Science and Technology Organisation

Vol. 29, No. 2 pp 63-68 (2001)
ABSTRACT: Detection of targets in the ocean using sound is traditionally achieved with either passive or active sonar. Acoustic daylight is a new technique being developed, which relies on the ambient noise in the ocean to provide the acoustic illumination necessary to detect a target. The presence of a target scatters some of the incident sound which can be collected by a suitable acoustic lens to produce an image of the target. An acoustic daylight imaging system developed at Scripps Institution of Oceanography is described and images obtained of planar, cylindrical and spherical targets are presented. It was able to image all targets, with varying resolution and contrast between the target and background. In some cases it was able to distinguish between different target compositions through the reflected spectral content. A more sophisticated imaging system being developed by the DSTO will also be described.

AN APPROACH TO ESTIMATION OF UNDERWATER HEARING THRESHOLDS AND NOISE EXPOSURE LIMITS

Kazuoki Kuramoto, Kensei Oimatsu, Shin'ya Kuwahara
Maritime Safety Academy, 5-1 Wakaba, Kure, 737-8512 Japan
Shizuma Yamaguchi
Faculty of Engineering, Yamaguchi University, Tokiwadai, Ube, 755-8611 Japan

Vol. 29, No. 2 pp 69-72 (2001)
ABSTRACT: There are many difficulties to carry out hearing tests in water, for example, the necessity of preparing audiometric equipment for underwater measurement and diving equipment (SCUBA) for breathing of subjects, unavoidable background noise from surrounding and so on. As a result, there are very few studies on establishing the hearing thresholds and noise exposure limits in water even though they are fundamental and important characteristics of underwater hearing in man. One of the most efficient approaches to acquire these standard values is through transposition from air to water. We attempted to establish the relationship between the perceived loudness in water and in air by conducting hearing tests in a water tank. By applying this relationship to available data on hearing threshold and noise exposure limit in air, we have estimated the equivalent thresholds and exposure limits in water.

RECENT DEVELOPMENTS IN THE DESIGN AND PERFORMANCE OF ROAD TRAFFIC NOISE BARRIERS

Stephen Samuels,
Director TEF Consulting and Visiting Research Fellow UNSW
Eric Ancieh,
Roads and Traffic Authority of NSW

Vol. 29, No. 2 pp 73-78 (2001)
ABSTRACT: This paper deals with some recent developments in the design and performance of roadside barriers that are applied as a means of controlling road traffic noise. It is a review paper that is based on the outcomes of literature and information searches undertaken for and on behalf of the Roads and Traffic Authority of NSW. Some interesting, ongoing developments in the design and performance of traffic noise barriers have been identified. In particular, three types of innovative barrier designs were identified that appear to offer the potential for increased attenuation without the need for substantial increases in barrier height. Each of these developments is considered in some detail in the paper and recommendations are made for the possibility of pursuing them further.

 

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