Sound-absorbing metasurface in diffuse field for large area applications

Abstract

Designing a thin sound absorber having the wide bandwidth in the low-frequency range has been a challenging problem, but recently, researches on the metamaterials or the metasurfaces are actively investigated. In this study, we propose an acoustic metasurface that absorbs sound energy perfectly at target frequencies based on hybrid resonance using an array of multiple-type Helmholtz resonators of subwavelength scale. Based on a theoretical model, we optimally design a unit cell of the proposed metasurface for perfect sound absorption at a target frequency. Since oblique incidence of the sound should be considered for a practical application of the proposed metasurface, we fabricate samples of periodic array of multiple unit cells for large area and the absorption of the sample in diffuse field are measured in a reverberation room. The present work is expected to open a possibility for potential applications of the proposed metasurface in room acoustics and architectural acoustics.