Optimal Audio Beam Pattern Synthesis for an Enhanced Parametric Array Loudspeaker

A parametric array loudspeaker (PAL) generates highly directional audible sound in air with a small aperture size compared to a conventional loudspeaker. But in indoor applications, the long propagation distance of a PAL causes reflections, which disturbs the reproduction of narrow audio beams. Moreover, sound distortion appears along the off-axis direction due to the frequency dependence of the beam width. This study proposed an optimal audio beam pattern synthesis for a PAL-based convex optimization, which can design the audio beam of a PAL with an optimal solution. The proposed method overcame the mentioned limitations by applying it to a length-limited PAL for audio spot control and a multichannel PAL array for a constant beam width audio beam. In a length-limited PAL, the proposed method restricts the audio spot to a smaller region and weakens the sound leakage along the off-axis direction. Whereas in a multichannel PAL array, the proposed method also achieves a constant beam width near the radiator axis. Simulations and experiments verify the effectiveness of the proposed method, which will enhance the performance of a PAL in scenarios where control of the audio beam is required.