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Vol 25 No 3

CONTENTS

December 1997


ARTICLES

The Prediction of Structure-borne Noise Transmission In Ships Using Statistical Energy Analysis
V K Tso and C H Hansen
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Finite Element Analysis and Gong Acoustics
N McLachlan
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A Discussion of the Australian National Standard for Occupational Noise
JH Macrae
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NOTES

An Innovative Use of Hay Bales to Provide Ventilation an Noise Control
RT Benbow
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50 Years of Helping People Hear
Natlonal Acoustlcs Laboratories
PDF Full Paper

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The Prediction of Structure-borne Noise Transmission In Ships Using Statistical Energy Analysis

Y. K. Tso
Department of Defence, Aeronautical and Maritime Research Laboratory - DSTO,
Flshermens Bend, Victoria 3207, Australia.

C. H. Hansen
Department of Mechanical Engineering, The University of Adelaide,
South Australia 5005, Australia.

Vol. 25, No. 3 pp 97-102 (1997)
ABSTRACT: This paper is concerned with the transmission of noise and vibration in ship structures, and in particular, naval ship structures. The first part of the paper presents a review of different methods for ship noise prediction. It then introduces the method of Statistical Energy Analysis (SEA) for the investigation of ship noise and vibration in the high frequency regions. Previous studies have shown that SEA is a useful tool for the analysis of vibration transmission in structures which consist mainly of plate elements. However, naval ship structures often involve more complex elements such as shells and beam stiffened plates. In the second part of the paper, two types of structure which are considered to be characteristic of naval ship constructions are identified. They are: a cylindrical shell coupled to an end plate; and a plate with periodic stiffeners coupled at right angles to a uniform plate. The Coupling Loss Factors (CLFs) of these two structures are evaluated, using travelling wave analysis, for SEA studies. Results from an experimental program confirm the validity of the formulation of CLFs.

Finite Element Analysis and Gong Acoustics

Neil McLachlan,
Department of Interior Design, RMIT
Melbourne, VIC 3001, Australia

Vol. 25, No. 3 pp 103-107 (1997)
ABSTRACT: Finite Element Analysis is used to predict the effect of a range of variations of gong geometries on modal frequencies. This data is evaluated in relation to experience in gong manufacture by a variety of methods and its implications for new instruments discussed.

A Discussion of the Australian National Standard for Occupational Noise

J. H. Macrae,
Hearing Assessment Research
National Acoustic Laboratories
126 Greville Street, Cbatswood NSW 2067, Australia

Vol. 25, No. 3 pp 109-112 (1997)
ABSTRACT: In 1974, the National Health and Medical Research Council warned that "the estimated risks associated with exposure to noise at levels of 85 and 90 dB(A) over a working life-time lead to an incidence of hearing loss in the working community which is unacceptable on medical grounds in the long term". Despite this warning, Australian legislatures set an 8-hour equivalent continuous A-weighted sound pressure level (LAeq,8hJ of 90 dB(A) as the occupational noise exposure limit until recent years. Partly as a result of this, occupational noise-induced hearing loss has continued to be a highly prevalent industrial disease in Australia and the associated costs of compensation have escalated since 1988. In response to this situation, the National Occupational Health and Safety Commission in 1992 declared an LAeq,8h of85 dB(A) as the Australian National Standard for Occupational Noise and this is gradually being adopted by Australian legislatures. However, given the current magnitude of the problem, a stricter limit seems appropriate. A standard of 80 dB(A) would come much closer to an acceptable solution to the problem of occupational noise-induced hearing loss.

An Innovative Use of Hay Bales to Provide Ventilation an Noise Control

R T Benbow, Dick Benbow & Assoc

Vol. 25, No. 3 pg 112 (1997)

50 Years of Helping People Hear

Natlonal Acoustlcs Laboratories

Vol. 25, No. 3 pg 113-114 (1997)

 

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