The active minimization of harmonic enclosed sound fields, part III: Experimental verification
The active minimization of harmonic enclosed sound fields, part III: Experimental verification
The principle objective of this paper is to compare the measured results of active minimization experiments in an enclosed sound field with those predicted from theory. The enclosure used was essentially two dimensional over the frequency range of interest and was only lightly damped. A practical control system was built which minimized the sum of the squares of a number of microphone outputs by adjusting the outputs of a number of secondary loudspeakers at a single frequency. Various approaches to designing the algorithm which controls such a system are discussed, including matrix inversion, gradient descent methods, and pattern search methods. Although some problems with coupling between the acoustic and structural modes were initially encountered, the response of the experimental enclosure was very close to that predicted by the computer model when these problems were overcome. The pressure field inside the enclosure was measured at 200 points when excited both on resonance and off resonance, and the form of the pressure field was also found to be very similar to that predicted by the computer model. The conditions under which significant reductions in the total acoustic potential energy in the enclosure could be achieved by the action of a number of secondary sources were experimentally investigated. It was found that, in general, large reductions can be achieved only when the enclosure is excited on resonance. The secondary source does not have to be within half a wavelength of the primary to give good reductions, provided it is able to couple in to the most strongly excited modes.
35-58
Elliott, S. J.
721dc55c-8c3e-4895-b9c4-82f62abd3567
Curtis, A. R.D.
79ce7e69-6528-4453-ac93-9f80c0bfc340
Bullmore, A. J.
320a3079-679c-4ef0-97ab-7bb0c632e9ad
Nelson, P. A.
5c6f5cc9-ea52-4fe2-9edf-05d696b0c1a9
22 August 1987
Elliott, S. J.
721dc55c-8c3e-4895-b9c4-82f62abd3567
Curtis, A. R.D.
79ce7e69-6528-4453-ac93-9f80c0bfc340
Bullmore, A. J.
320a3079-679c-4ef0-97ab-7bb0c632e9ad
Nelson, P. A.
5c6f5cc9-ea52-4fe2-9edf-05d696b0c1a9
Elliott, S. J., Curtis, A. R.D., Bullmore, A. J. and Nelson, P. A.
(1987)
The active minimization of harmonic enclosed sound fields, part III: Experimental verification.
Journal of Sound and Vibration, 117 (1), .
(doi:10.1016/0022-460X(87)90434-2).
Abstract
The principle objective of this paper is to compare the measured results of active minimization experiments in an enclosed sound field with those predicted from theory. The enclosure used was essentially two dimensional over the frequency range of interest and was only lightly damped. A practical control system was built which minimized the sum of the squares of a number of microphone outputs by adjusting the outputs of a number of secondary loudspeakers at a single frequency. Various approaches to designing the algorithm which controls such a system are discussed, including matrix inversion, gradient descent methods, and pattern search methods. Although some problems with coupling between the acoustic and structural modes were initially encountered, the response of the experimental enclosure was very close to that predicted by the computer model when these problems were overcome. The pressure field inside the enclosure was measured at 200 points when excited both on resonance and off resonance, and the form of the pressure field was also found to be very similar to that predicted by the computer model. The conditions under which significant reductions in the total acoustic potential energy in the enclosure could be achieved by the action of a number of secondary sources were experimentally investigated. It was found that, in general, large reductions can be achieved only when the enclosure is excited on resonance. The secondary source does not have to be within half a wavelength of the primary to give good reductions, provided it is able to couple in to the most strongly excited modes.
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Published date: 22 August 1987
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Funding Information:
ACKNOWLEDGMENT S. J. Elliott and P. A. Nelson are supported by the Science and Engineering Research Council under the Special Replacement Scheme; the Department of Trade and Industry for a research grant which supports A. R. D. Curtis and A. J. Bullmore also is gratefully acknowledged.
Copyright:
Copyright 2014 Elsevier B.V., All rights reserved.
Identifiers
Local EPrints ID: 468576
URI: http://eprints.soton.ac.uk/id/eprint/468576
ISSN: 0022-460X
PURE UUID: aed5791a-0bd9-41bf-8af7-9edb6522c53f
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Date deposited: 18 Aug 2022 16:40
Last modified: 18 Mar 2024 02:31
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Author:
A. R.D. Curtis
Author:
A. J. Bullmore
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