Reduction of Multichannel Sound System Based on Spherical Harmonics

In order to meet people's demand for 3D audio in family, it's a critical problem to recreate a 3D spatial sound field with few loudspeakers. In this paper, we introduce a L- to L-1-channel reduction method based on spherical harmonic decomposition and sound field of head can be perfectly reproduced. When loudspeakers are too few to perfectly reproduce the sound field of head, we ensure low distortions of sound field at ears. On this basis, multichannel reduction algorithm from L- to M-channel system is proposed. As an example, reduction of NHK 22.2 system has been implemented and eleven loudspeaker arrangements from 22 to 6 channels are derived. Results show the sound field of head can be reproduced perfectly until 10 channels and 8-, 6-channel systems can keep low distortions at ears. Compared with Ando's multichannel conversion method by subjective evaluation, our proposed method is better in terms of sound localization.