A nonlinear sound field control method for a multi-channel parametric array loudspeaker array

A parametric array loudspeaker (PAL) generates a highly directional audible sound beam. However, indoor scattering and reflecting effects diminish its advantage of high directivity, causing the scattered or reflected sound to appear in undesired regions. Deriving from the Westervelt equation, the nonlinear coupling exists between each channel, rendering linear sound field control algorithms ineffective. This paper proposes a framework of nonlinear sound field control, enabling the manipulation of nonlinear sound fields generated by the PAL in complicated acoustic environments. Besides, PAL often faces challenges in radiation efficiency due to the poor conversion efficiency of nonlinear sound. Therefore, a sound control algorithm suitable for PAL is proposed, which maximizes radiation efficiency while ensuring acoustic contrast through a two-stage non-convex optimization procedure. The simulations and experimental results verify the effectiveness of the proposed framework and algorithm of nonlinear sound field control. The undesired audible sound in the dark zone is suppressed while maintaining the desired audible sound in the bright zone. This enhances the performance of a PAL in real scenarios with existing scattering or reflecting effects.