Spherical Harmonic Decomposition of a Sound Field Based on Microphones Around the Circumference of a Human Head

Abstract

We present a method for decomposing a sound field into spherical harmonics (SH) based on observations of the sound field around the circumference of a human head. The method is based on the analytical solution for observations of the sound field along the equator of a rigid sphere that we presented recently. The present method incorporates a calibration stage in which the microphone signals for sound sources at a suitable set of calibration positions are projected onto the SH decomposition of the same sound field on the surface of a notional rigid sphere by means of a linear filtering operation. The filter coefficients are computed from the calibration data via a least-squares fit. We present an evaluation of the method based on binaural rendering of numerically simulated signals for an array of 18 microphones providing 8th SH order to demonstrate its effectiveness