Spherical loudspeaker array beamforming in enclosed sound fields by MIMO optimization

Abstract

Spherical loudspeaker arrays have been recently studied for a variety of applications such as spatial sound reproduction and room acoustics. Array directivity is typically designed for free field, although loudspeaker arrays often operate in enclosures. Therefore, current methods for directivity design may not be suitable. We present a new method for designing loudspeaker array directivity in enclosures, where the direct sound measured by a microphone array is emphasized compared to room reflections. The two spherical arrays form an acoustic multiple-input multiple-output (MIMO) system for which the loudspeaker array beamforming coefficients are designed based on the system transfer matrix. The proposed method uses the average output of the microphone array, over all look directions to avoid signal cancellation due to room reflections. The performance of the proposed method is studied through a simulation example.