Acoustic bianisotropy in effective fluids of finite domain

Recent research has shown that subwavelength asymmetry and/or nonlocal effects in heterogeneous acoustic media can be described as a dynamic effective fluid displaying acoustic bianisotropic properties. Theoretical homogenization schemes have demonstrated emergent acoustic bianisotropy for an infinite array of subwavelength inhomogeneities in a fluid matrix, and experimental studies have demonstrated individual asymmetric microstructures and single layer metasurfaces exhibiting bianisotropy. However, metamaterials research has shown that a finite domain effective fluid behaves unlike an infinite domain or a surface, and the effective properties of the domain tend to depend on the chosen boundaries and on the position within the domain, even when the microstructure is periodic. This work presents the use of multiple scattering homogenization to discuss the dependence of bianisotropic properties of finite effective fluids on the choice of boundaries and domain size in order to inform future experimental studies on acoustic bianisotropy. [Work supported by the Office of Naval Research and the NRC Research Associateship Program.]