Highly efficient anomalous refraction of airborne sound through ultrathin metasurfaces

TL;DR

This paper introduces a novel ultrathin metasurface lens that efficiently deflects airborne sound in an anomalous manner, enabling advanced sound control with minimal device thickness for practical applications.

Contribution

The study presents a new design of ultrathin, coiling-slit metasurfaces for anomalous sound refraction, achieving high performance in a flat, subwavelength-thickness device.

Findings

Experimental results match theoretical predictions.

High efficiency in steering airborne sound wavefronts.

Potential for practical indoor sound control applications.

Abstract

Similar to their optic counterparts, acoustic components are anticipated to flexibly tailor the propagation of sound. However, the practical applications, e.g. for audible sound with large wavelengths, are frequently hampered by the issue of device thickness. Here we present an effective design of metasurface structures that can deflect the transmitted airborne sound in an anomalous way. This flat lens, made of spatially varied coiling-slit subunits, has a thickness of deep subwavelength. By elaborately optimizing its microstructures, the proposed lens exhibits high performance in steering sound wavefronts. The experimental results are in excellent agreement with the theoretical predictions. This study may open new avenues for numerous daily life applications, such as controlling indoor sound effects by decorating rooms with light metasurface walls.