Directional sound source modeling for acoustic finite-difference time-domain analysis by using spherical harmonics

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Other Title
  • 球面調和関数を利用した音響FDTD解析における指向性音源モデル
  • キュウメン チョウワ カンスウ オ リヨウ シタ オンキョウ FDTD カイセキ ニ オケル シコウセイオン ゲン モデル

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Abstract

For reproducing and evaluating acoustical environment in general spaces, directivity of sound source is one of important factors determining the quality of acoustics. Directivity of a sound source originates from the source’s shape and its size relative to wavelength. In order to precisely simulate a directivity of a source by wave-based numerical analysis, modeling the shape of the source geometrically in detail is the physically most appropriate. In the case of sources with complex shapes, however, geometrically precise modeling of the source shape requires small size of spatial discretization, and such a fine mesh generation results in huge computational costs and leads difficulty of practical computation. In this study, applying a basic theory of Fourier analysis in which arbitrary directivity can be constructed by linear combination of spherical harmonics, the condition of the sound source for the finite-difference time-domain method to reduce computational cost and to enable efficient analysis against a source with complex directivity characteristics was investigated. Spatial distribution of sound pressure of initial condition for respective spherical harmonic function, and correction method of spectral characteristics for the finite-difference time-domain analysis are described. The applicability of the method was validated through an application to source directivity of a head and torso simulator with a mouth simulator.

Journal

  • SEISAN KENKYU

    SEISAN KENKYU 65 (3), 287-294, 2013

    Institute of Industrial Science The University of Tokyo

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