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Vol 25 No 2

CONTENTS

August 1997


ARTICLES

Acoustical Research in Australia
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Active Isolation of a Vibrating Mass
C Q Howard and C H Hansen
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Sound In the Animal World
N Fletcher
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Validation of Environmental Noise Model (ENM Windows)
R Tonin
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Acoustical Research in Australia

Vol. 25, No. 2 pp 49-63 (1997)
ABSTRACT: A brief review is given of Australian research and devel opment work in a wide range of areas of acoustics. Areas covered include measurement and calibration, human hearing, biological acoustics, musical acoustics, ultrasonics, underwater acoustics, active noise and vibration control, mechanical vibration, building and industrial acoustics, and environmental acoustics.

Active Isolation of a Vibrating Mass

C.Q. Howard and C.H. Hansen,
Dept. of Mechanical Engineering,
University of Adelaide,
South Australia 5005, Australia

Vol. 25, No. 2 pp 65-67 (1997)
ABSTRACT: Active vibration isolation can olTer improved performance at low frequencies compared with passive isolation. Active control methods require the selection of a suitable cost function to be minimised. Experimental results are presented of the active vibration isolation of a simulated rotating machine mounted to a beam which uses two types of cost function, the force and acceleration respectively at the base of the isolator. The results show that minimisation of one type of cost function does not necessarily lead to the minimisation of the other cost function.

Sound In the Animal World

Neville Fletcher
Acoustics and Vibration Unit, Dept. of Aerospace and Mechanical Engineering
Australian Defence Force Academy
Canberra 2600

Vol. 25, No. 2 pp 69-74 (1997)
ABSTRACT: Energy relations involved in sound production by animals are examined, and it is found that different animals devote vastly different fractions of their available muscular energy to this form of communication. Typical sound energy output is found to range from a fraction of a watt for particularly noisy animals, through a typical value of around a milliwatt, and down to a microwatt or less for tiny insects. Consideration of atmospheric propagation and background noise suggests an optimal song frequency for a given available acoustic power, the preferred frequency for a power near ImW being in the range I to 10kHz. Mechanical and pneumatic methods of sound production employed by animals are reviewed, and brief consideration is given to auditory systems and to the encoding of information in vocal utterances.

Validation of Environmental Noise Model (ENM Windows)

Renzo Tonin,
Renzo Tonin & Associates Pty Ltd
Level 16,9 Castlereagh St.,
Sydney NSW 2000, Australia

Vol. 25, No. 2 pp 75-79 (1997)

 

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