Focused sound generation using configurable holographic acoustic admittance panels

In this study, we design and demonstrate a novel adjustable acoustic flat lens by assembling three beamforming holographic admittance acoustic metasurface panels. Each admittance panel is constructed using variable-depth square grooves arranged in a square lattice. We provide a detailed design methodology for the acoustic metasurface panels, highlighting the key parameters used. Both numerical simulations and experimental results are presented to verify acoustic focusing at 30 kHz. The results indicate that, by using the acoustic lens formed by three panels radiating at an angle of 45 degrees, the acoustic pressure can be amplified by up to three times compared to the case without the lens. Furthermore, we demonstrate that the lens concept presented here can easily adjust the focal length and focal point by dynamic variations of the geometric parameters. We also show that optimal amplification, up to four times greater than without the lens, can be achieved through numerical predictions based on effective material parameters. This research underscores the versatility of acoustic metasurfaces in manipulating sound waves and suggests avenues for further enhancement of acoustic lens efficiency.