Acoustical holography in spherical coordinates for noise source identification

Abstract

The present work was conducted in order both to confirm the accuracy of spherical holography in simulation, and to extend its application to noise source identification for small machines, specifically a refrigeration compressor. As employed here the technique involves using sound pressure and referenced phase data on the measurement spare to determine the spherical harmonic coefficients. Those coefficients are then used to propagate and reconstruct the sound field in either of two directions: Outward, to visualize the sound field, or inward for the purpose of noise source identification. The acoustic particle velocity can be calculated so that its distribution over the surface of the source may be visualized. The pressure and velocity results can then be combined to yield the acoustic intensity.