Impulse response of a spherical microphone array (eigenmike)

Abstract

Spherical microphone arrays are capable of complete three-dimensional sound field capture and robust noise cancellation [J. Meyer & G.W. Elko, ‘‘A Highly Scalable Spherical Microphone Array Based on an Orthonormal Decomposition of the Soundfield,’’ in Proc. IEEE Int. Conf. Acoust., Speech, Signal Processing, 2002, Vol. II, pp. 1781–1784]. The spherical array tested has 24 omni-directional pressure microphones arranged on a rigid sphere. The sound pressure from each sensor is decomposed into spherical harmonics (standard eigen analysis) which results in rotationally symmetric output along any axis (three dimensionally) through the center of the sphere. An accurate impulse response of this system is important to sound localization and tracking methods. Time history can also be used to enhance the prediction model for source movement. The impulse measurements on this array were made in a semi-anechoic chamber and are in good agreement with expected results. The three main characteristics of the impulse response that will be discussed are the delay times, amplitude differences, and frequency response.