The spherical-shell microphone array

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Abstract

Spherical microphone arrays have been recently studied for a wide range of applications. In particular, microphones arranged around an open or virtual sphere are useful in scanning microphone arrays for sound field analysis. However, open-sphere spherical arrays have been shown to have poor robustness at frequencies related to the zeros of the spherical Bessel functions. This paper presents a framework for the analysis of array robustness using the condition number of a given matrix, and then proposes several robust array configurations. In particular, a dual-sphere configuration previously presented which uses twice as many microphones compared to a single-sphere configuration is analyzed. This paper then shows that high robustness can be achieved without increasing the number of microphones by arranging the microphones in the volume of a spherical shell. Another simpler configuration employs a single sphere and an additional microphone at the sphere center, showing improved robustness at the low-frequency range. Finally, the white-noise gain of the arrays is investigated verifying that improved white-noise gain is associated with lower matrix condition number.

Original languageEnglish
Article number4472221
Pages (from-to)740-747
Number of pages8
JournalIEEE Transactions on Audio, Speech and Language Processing
Volume16
Issue number4
DOIs
StatePublished - 1 May 2008

Keywords

  • Array processing
  • Numerical conditioning
  • Spherical harmonics
  • Spherical microphone arrays
  • White-noise gain

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