Experimental study of nonlinear acoustic metamaterials

Recently, there is a growing desire in achieving the unprecedented control over sounds using nonlinear materials or structures. Nonlinear effects happen usually under high-intensity excitations. This has imposed one of main obstacles blocking the practical realization of acoustic control using nonlinearity. In this study, we have proposed a membrane-type acoustic metamaterial that could exhibit strong nonlinear effects under very low amplitude of operation. The proposed nonlinear metamaterials possess the bistability, realized by dual attracting forces exerted from two magnets. Nonlinear acoustic features have been identified experimentally in an one-dimensional wave-guiding system. We have also developed a FDTD method for modelling the nonlinearity of metamaterials. Our study is expected to open a new avenue towards airborne sound control with artificial nonlinear metamaterials.