Generation of Isolated Wideband Sound Fields Using a Combined Two-stage Lasso-LS Algorithm

The prohibitive number of speakers required for the reproduction of isolated soundfields is the major limitation preventing solution deployment. This paper addresses the provision of personal soundfields (zones) to multiple listeners using a limited number of speakers with an underlying assumption of fixed virtual sources. For such multizone systems, optimization of speaker positions and weightings is important to reduce the number of active speakers. Typically, single stage optimization is performed, but in this paper a new two-stage pressure matching optimization is proposed for wideband sound sources. In the first stage, the least-absolute shrinkage and selection operator (Lasso) is used to select the speakers' positions for all sources and frequency bands. A second stage then optimizes reproduction using all selected speakers on the basis of a regularized least-squares (LS) algorithm. The performance of the new, two-stage approach is investigated for different reproduction angles, frequency range and variable total speaker weight powers. The results demonstrate that using two-stage Lasso-LS optimization can give up to 69 dB improvement in the mean squared error (MSE) over a single-stage LS in the reproduction of two isolated audio signals within control zones using e.g. 84 speakers.