On the applicability of the spherical wave expansion with a single origin for near-field acoustical holography

J. Gomes, J. Hald, P. Juhl, Finn Jacobsen

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Abstract

The spherical wave expansion with a single origin is sometimes used in connection with near-field acoustical holography to determine the sound field on the surface of a source. The radiated field is approximated by a truncated expansion, and the expansion coefficients are determined by matching the sound field model to the measured pressure close to the source. This problem is ill posed, and therefore regularization is required. The present paper investigates the consequence of using only the expansion truncation as regularization approach and compares it with results obtained when additional regularization (the truncated singular value decomposition) is introduced. Important differences between applying the method when using a microphone array surrounding the source completely and an array covering only a part of the source are described. Another relevant issue is the scaling of the wave functions. It is shown that it is important for the additional regularization to work properly that the wave functions are scaled in such a way that their magnitude on the measurement surface decreases with the order. Finally, the method is applied on nonspherical sources using a vibrating plate in both simulations and an experiment, and the performance is compared with the equivalent source method.
Original languageEnglish
JournalJournal of the Acoustical Society of America
Volume125
Issue number3
Pages (from-to)1529-1537
ISSN0001-4966
DOIs
Publication statusPublished - 2009

Bibliographical note

Copyright (2009) Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America.

Keywords

  • vibrations
  • singular value decomposition
  • plates (structures)
  • acoustic holography
  • acoustic wave propagation
  • structural acoustics

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