Confining and channeling sound through coupled resonators

TL;DR

This paper introduces a Helmholtz resonator-based subwavelength sound channel at metamaterial interfaces, demonstrating robust sound confinement and the potential for point confinement through controlled disorder.

Contribution

It presents a novel sound confinement method using coupled resonators at metamaterial interfaces, with robustness to disorder and potential for acoustic circuit applications.

Findings

Significant pressure reduction within the channel

Large increase in acoustic impedance outside the channel

Robustness of sound confinement to frequency and spatial disorder

Abstract

Confining sound is of significant importance for the manipulation and routing acoustic waves. We propose a Helmholtz resonator (HR) based subwavelength sound channel formed at the interface of two metamaterials, for this purpose. The confinement is quantified through (i) a substantial reduction of the pressure, and (ii) an increase in a specific acoustic impedance (defined by the ratio of the local pressure to the sound velocity) - to a very large value outside the channel. The sound confinement is robust to frequency as well as spatial disorder at the interface, as long as the interface related edge mode is situated within the band gap. A closed acoustic circuit was formed by introducing controlled disorder in the HR units at the corners, indicating the possibility of confining sound to a point.