Ultra-broadband acoustic metasurface for speaker directivity control

Abstract

Acoustic metasurfaces have shown remarkable capabilities for shaping acoustic wavefronts. However, most thin metamaterials can only work well for a narrow range of acoustic frequencies. This limitation has thus far dramatically limited their potential for human-based audio and acoustic applications. Here we present a generic acoustic metasurface design approach to reshape acoustic wavefronts in a broad bandwidth. As a demonstration, we designed two acoustic lenses. The first acoustic lens converts a 4-in. speaker into an omnidirectional source, covering a frequency range from 1 to 10kHz. The second acoustic lens delivers super-directionality for a 1-in. speaker from 1 to 20 kHz. Experimental measurements showed great agreement with the simulations. Our design approach enables the design of ultra-broadband metasurfaces useful for audio applications.