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Active control of the sound power scattered by a locally-reacting sphere

Active control of the sound power scattered by a locally-reacting sphere
Active control of the sound power scattered by a locally-reacting sphere
Active control of the sound power scattered by a sphere is theoretically investigated using spherical harmonic expansions of the primary and secondary fields. The sphere has a surface impedance that is uniform, real, and locally reacting while being subjected to an incident monochromatic plane wave. The scattered power is controlled with a number of monopole sources, initially on the surface of the sphere, and is expressed as the sum of squared amplitudes of the spherical harmonics due to both the scattered and control fields. This quadratic function is minimized to identify the optimal strengths for different numbers of control sources. At low frequencies, the scattered field is dominated by the first few spherical harmonic terms, and its power can be significantly reduced with a single controlling monopole for a soft or absorbent sphere and with two monopoles for a hard sphere. The number of secondary sources required to significantly attenuate the scattered field at higher frequencies is found to be proportional to the square of the frequency, and the attenuation also falls off rapidly if the secondary sources are moved away from the surface of the sphere, no matter what its surface impedance.
0001-4966
1851-1862
Elliott, Stephen
721dc55c-8c3e-4895-b9c4-82f62abd3567
Oriță, Mihai
b5850bb4-8337-4865-bb8f-50860169bee0
Cheer, Jordan
8e452f50-4c7d-4d4e-913a-34015e99b9dc
Elliott, Stephen
721dc55c-8c3e-4895-b9c4-82f62abd3567
Oriță, Mihai
b5850bb4-8337-4865-bb8f-50860169bee0
Cheer, Jordan
8e452f50-4c7d-4d4e-913a-34015e99b9dc

Elliott, Stephen, Oriță, Mihai and Cheer, Jordan (2020) Active control of the sound power scattered by a locally-reacting sphere. Journal of the Acoustical Society of America, 147 (3), 1851-1862. (doi:10.1121/10.0000843).

Record type: Article

Abstract

Active control of the sound power scattered by a sphere is theoretically investigated using spherical harmonic expansions of the primary and secondary fields. The sphere has a surface impedance that is uniform, real, and locally reacting while being subjected to an incident monochromatic plane wave. The scattered power is controlled with a number of monopole sources, initially on the surface of the sphere, and is expressed as the sum of squared amplitudes of the spherical harmonics due to both the scattered and control fields. This quadratic function is minimized to identify the optimal strengths for different numbers of control sources. At low frequencies, the scattered field is dominated by the first few spherical harmonic terms, and its power can be significantly reduced with a single controlling monopole for a soft or absorbent sphere and with two monopoles for a hard sphere. The number of secondary sources required to significantly attenuate the scattered field at higher frequencies is found to be proportional to the square of the frequency, and the attenuation also falls off rapidly if the secondary sources are moved away from the surface of the sphere, no matter what its surface impedance.

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AC_Scattering - Accepted Manuscript
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Accepted/In Press date: 13 February 2020
e-pub ahead of print date: 23 March 2020
Published date: 23 March 2020
Additional Information: Publisher Copyright: © 2020 Acoustical Society of America. Copyright: Copyright 2020 Elsevier B.V., All rights reserved.

Identifiers

Local EPrints ID: 438955
URI: http://eprints.soton.ac.uk/id/eprint/438955
ISSN: 0001-4966
PURE UUID: 868bd48f-1667-4506-b90f-1afc786a4335
ORCID for Mihai Oriță: ORCID iD orcid.org/0000-0001-7307-0497
ORCID for Jordan Cheer: ORCID iD orcid.org/0000-0002-0552-5506

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Date deposited: 30 Mar 2020 16:30
Last modified: 17 Mar 2024 05:26

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Contributors

Author: Stephen Elliott
Author: Mihai Oriță ORCID iD
Author: Jordan Cheer ORCID iD

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