Multiband ventilation barriers enabled by space-coiling acoustic metamaterials

Abstract

In this study, space-coiling acoustic metamaterials were employed to achieve multiband sound insulation for ventilation acoustic barriers. Based on the ability of space-coiling metamaterials to manipulate acoustic waves, multiple resonances are introduced by tuning the effective refractive indices of internally curled channels, especially for low-frequency sound. This paper presents an analytical model of the proposed structure and its corresponding band structure, demonstrating that the acoustic barrier reported herein suppresses the transmission of acoustic waves by the band-folding effect as well as local resonance. To confirm the underlying mechanisms, effective parameters and equi-frequency contours were evaluated. The normal sound transmission loss was determined numerically and experimentally, and the effectiveness of the ventilation barrier in a diffuse field was confirmed by conducting numerical simulations.