The parametric array loudspeaker (PAL) enables the generation of highly localized sound zones through beam focusing, even with a subwavelength-sized source. However, conventional multi-channel PAL arrays require expensive and complex array signal processing. To address this limitation, we developed a planar acoustic metasurface based on space-coiling structures that achieves beam focusing for a single-channel PAL. The metasurface was designed to focus at 100 mm away from the source at 40 kHz. Finite element simulations and experimental measurements confirmed the formation of a focal point at approximately 100 mm from 500 to 4 kHz. Our work provides a cost-effective solution for focused sound zone generation in applications where audio privacy may be essential—such as in vehicles and personal audio systems.
Kim et al. (2025) studied this question.