Programming Reflected and Transmitted Sound Behaviors Based on Motor‐Driven Digital Metasurface

Abstract

Acoustic metasurfaces have shown indispensable abilities for wave control with subwavelength resolution and enabled exotic sound functions unavailable using naturally occurring materials. To further improve the utilization of sound field resources and enhance the coverage of acoustic signals, full‐space acoustic metasurfaces hold great potential for independent tailoring of reflected and transmitted waves. However, achieving dynamic manipulation of the full sound field in a programmable fashion has remained inaccessible until now. Here, a computer‐controlled motor‐driven acoustic metasurface is proposed and designed to program the reflected and transmitted sound behaviors without crosstalk. The metasurface elements consist of a stationary cuboid and a rotatable lid connecting with an individually programmable micromotor. Eight distinct resonant substructures with specific wave responses are integrated inherently in the cuboid, and the lid can be rotated automatically to select one of them at a time, and therefore, the proposed metasurface enables 2‐bit phase adjustment. For ever‐changing coding instructions, the metasurface can choose to modulate reflected or transmitted waves in real time. To show the capabilities of the presented programmable acoustic metasurface, two typical functions are demonstrated: dynamic acoustic focusing and variable acoustic holograms in both reflection and transmission modes.