Microslit-embedded acoustic metasurface for bandpass filter shaped sound absorption

Abstract

This paper presents a proposal of sub-wavelength acoustic metasurface (AMS) sound absorbers, designated as MeAMS absorbers, with coupled-microslit resonators of gradually decreasing sizes in the respective component resonators. A MeAMS absorber can provide bandpass filter-shaped near-perfect absorption. The prediction theory of the present AMS absorbers is also proposed with two design methods to ascertain the dimensions of respective component resonators. The theory for AMS absorbers composed of single-microslit resonators is first verified with finite element method (FEM) simulation using thermoviscous boundary layer impedance boundary conditions. It is validated further for two 3D printed samples by an impedance tube measurement. Then, the theoretical predictability of absorption characteristics of MeAMS absorbers is discussed via FEM simulations and the impedance tube measurement for three 3D printed samples, revealing that the present theory provides a reasonable approximation of the absorption characteristics of MeAMS absorbers. Two one-third octave band near-perfect absorbers are also presented for practical applications.