Comparison of Strategies for Accurate Reproduction of a Target Signal with Compact Arrays of Loudspeakers for the Generation of Zones of Private Sound and Silence

Compact loudspeaker arrays can be driven so that the radiation patterns produce zones of private sound and zones of silence. This research compares the performance of two strategies, both based on the Pressure Matching Method (PMM), for accurate reproduction of a target signal. The first strategy is the Weighted PMM (WPMM) with low values for the weight of the reproduction error in the zone where accurate reproduction is not targeted. The second strategy is the Linearly-Constrained PMM (LCPMM), wherein a performance constraint on the accuracy of the target signal in a given zone is added to the cost function for the calculation of the input signals. Performance of the two methods was evaluated using numerical simulations of monopoles in free field and a linear array prototype with measured transfer functions in an anechoic environment. The two strategies were evaluated using a target signal with large amplitude variations between the so-called acoustically bright and dark zones. Results show that input signals designed with the WPMM provide better trade-offs between accuracy of the target field reproduction in the bright zone and directivity performance compared to that of the LCPMM.