Interface transmittance and interface waves in acoustic Willis media

Abstract

Acoustics Willis media, known as bianisotropic acoustic media, incorporate additional coupling between pressure and velocity and between momentum and volumetric strain in their constitutive equation. The extra coupling terms have a significant influence on acoustic wave behavior. In this paper, the unusual wave phenomena relevant to interfaces between homogeneous acoustic Willis media are theoretically studied. We show that Willis media offer more flexible control in wave front and energy flow when waves are transmitted through an interface. Different from traditional acoustic fluid, Willis acoustic media support edge and interface waves, for which the existence conditions and corresponding wave features are systematically investigated. The study unveils more possibilities for manipulating acoustic waves and may inspire new functional designs with acoustic Willis metamaterials.