Confining and channeling sound through coupled resonators

Abstract

Confining sound is of significant importance for the manipulation and routing of 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 bandgap. 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.