A Porous Medium As an Acoustic Metamaterial with Negative Inertial and Elastic Properties

Abstract

Abstract—The paper considers the effective inertial and elastic properties of a dispersive composite in the form of an elastic porous medium with empty spherical cavities. It is shown that when the translational vibrations and bulk oscillations of the cavities are in resonance, the dynamic density and compressibility of the porous medium take negative values. Estimates are presented for the internal dynamic parameters, for which the inertial and elastic properties determining the phase velocity and sound attenuation can simultaneously be negative in certain frequency ranges. The porous medium then assumes the properties of a metamaterial with negative sound refraction and other unique acoustic effects.