Perfect and broadband acoustic absorption by critical coupling

TL;DR

This paper demonstrates broadband and narrowband perfect acoustic absorption using critical coupling in two waveguide-resonator geometries, combining experimental and analytical methods to reveal mechanisms for nearly perfect energy absorption.

Contribution

It introduces two novel geometries for acoustic absorption employing critical coupling, advancing the understanding of energy leakage and loss interplay for perfect absorption.

Findings

Achieved broadband and narrowband perfect absorption experimentally.

Identified the role of energy leakage and inherent losses in absorption.

Demonstrated potential for designing broadband perfect absorbers.

Abstract

We experimentally and analytically report broadband and narrowband perfect absorption in two different acoustic waveguide-resonator geometries by the mechanism of critical coupling. In the first geometry the resonator (a Helmholtz resonator) is side-loaded to the waveguide and it has a moderate quality factor. In the second geometry the resonator (a viscoelastic porous plate) is in-line loaded and it contains two resonant modes with low quality factor. The interplay between the energy leakage of the resonant modes into the waveguide and the inherent losses of the system reveals a perfect and a broadband nearly perfect absorption. The results shown in this work can motivate relevant research for the design of broadband perfect absorbers in other domains of wave physics.