| Vol 28 No 1 | CONTENTS |
April 2000 |
Vibrato Frequency and Phase Lock in Operatic Duet Quality
M. Duncan, C. Williams and G. Troup
Rethinking Our Approach to Aircraft Noise Information - Going Beyond ANEF
D. Southgate
Methods to Measure the Four-Pole Parameters of Vibration Isolators
J. D. Dickens
Hearing Among Musicians and Music Performance
Donald Woolford
Some Applications of Numerical Acoustics
Joseph Lai
Books
News
New Members
Letter
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Diary
Acoustics Australia Information
Australian Acoustical Society Information
Advertisers Index
Melanie Duncan*, Carol Williams** and Gordon Troup***
*Music Department, **School of Historical and Gender Studies, ***Physics Department,
Monash University, Clayton, Victoria
Vol. 28, No. 1 pp 5-9 (2000)
ABSTRACT: For a 'bel canto' trained singer, 'vibrato' is defined as a periodic variation of the fundamental frequency of the sung note, with an intensity variation of the same period. 'Tremolo' is a variation in the intensity only. The locking of vibrato frequencies in unison soprano choirs has been reported and studied. A 1982 review article on the physics of the singing voice suggests that the pleasing or less pleasing quality of harmony in a vocal duet, for example, depends on whether or not the vibratos of the singers synchronise. This does not appear to have been investigated. Recordings of Dame Joan Sutherland singing the "Flower Duet" from the opera Lakme by Delibes with each of 3 different singers were studied. The powerful SpectraPro software was used for analysis. Our results show one singer locking in phase with Dame Joan, another locking in antiphase and another exhibiting phase wander. It is quite remarkable that such a complicatedly coupled system should behave so like a classically coupled oscillator system, for which in phase, and out of phase locking is possible, as is also phase wander. Psychophysical coupling clearly occurs.
D. Southgate
Airports Operations, Commonwealth Department of Transport and Regional Services, GPO Box 594, Canberra ACT 2601
Vol. 28, No. 1 pp 11-14 (2000)
ABSTRACT: A large number of environmental noise practitioners have had some involvement with aircraft noise issues and the Australian Noise Exposure Forecast (ANEF) system over the past twenty years. While the noise specialist generally finds the system rational and easy to use this is not the case for many decision-makers and members of the public. These latter groups treat the system, at best, with deep suspicion. Much of this negative attitude arose because of the way the ANEF was used in the EIS for the third runway at Sydney Airport - there was a widely held view that the EIS gave a very misleading picture of future aircraft noise distribution. In an attempt to gain back ground different ways to communicate with non-specialists on aircraft noise are now being developed by the Commonwealth Department of Transport and Regional Services. These 'new' approaches are based on 'number of events', rather than cumulated energy, descriptors since these more closely relate to the way a person is exposed to, and thinks about, aircraft noise. Very importantly detailed aircraft noise information is now being produced for areas which extend well beyond those covered by conventional ANEF contours.
J. D. Dickens
Maritime Platforms Division
Defence Science and Technology Organisation (DSTO),
Aeronautical and Maritime Research Laboratory (AMRL),
PO Box 4331, Melbourne, Victoria, Australia 3001
Vol. 28, No. 1 pp 15-21 (2000)
ABSTRACT: This paper describes the background to the development of a test facility and associated methods for measuring the four-pole parameters of vibration isolators under service conditions. The experimental methods of measuring the four-pole parameters of passive and active vibration isolators are discussed. Improvements to the measurement techniques are outlined, and implemented in a test rig capable of testing passive, semi-passive and active vibration isolators with feedback control.
HEARING AMONG MUSICIANS AND MUSIC PERFORMANCE
Donald Woolford
W-P-Consulting Pty Ltd
GPO Box 278, Sydney NSW 2001.
Vol. 28, No. 1 pp 23-24 (2000)
A Transcript of Ockham's Razor program with Robyn Williams and Donald Woolford, Broadcast over ABC Radio National on November 21, 1999.
SOME APPLICATIONS OF NUMERICAL ACOUSTICS
Joseph Lai
Acoustics and Vibration Unit
School of Aerospace & Mechanical Engineering
University College, The University of New South Wales,
Australian Defence Force Academy, Canberra, ACT 2600, Australia.
Vol. 28, No. 1 pp 25-29 (2000)
ABSTRACT: The advantages and disadvantages of finite element and boundary element methods and geometrical acoustics methods are discussed. Applications of these methods to solving a range of vibro-acoustics problems and architectural acoustic problems are illustrated with practical examples including structural radiation, noise barriers and acoustic quality of rooms. In all these examples, comparisons of predictions are made with measurements to illustrate the accuracies, limitations and usefulness of these numerical methods.