Optimisation of the target sound fields for the generation of independent listening zones in a reverberant environment

The Pressure Matching Method (PMM) has been widely used in individual listening zones (ILZ) systems to create multiple independent sound zones in the same environment. This method aims to reproduce a set of target acoustic fields in several control zones, using one or more loudspeaker arrays. These target fields are parameters of the ILZ algorithm that are defined at the design stage. In this work, we compare the effects of several target sound field alternatives on the sound field control system performance and robustness. The proposed target fields prevent the ILZ system from focusing its effort on unessential tasks such as the dereverberation of the acoustic environment. More specifically, we compare target acoustic fields of a single active loudspeaker, of several active and in-phase loudspeakers or of a set of loudspeakers acting as a beamformer steered towards one of the zones to be controlled. Results of simulations and experiments obtained with one compact loudspeaker array in the interior of a real car are presented as well as a study on the robustness to perturbations of the solutions obtained with the various choices of target acoustic fields.