Three-Dimensional Acoustic Metamaterial with Localized Resonances

Abstract

A three-dimensional acoustic negative refractive index metamaterial based on the idea of localized resonant structures is designed in the long-wavelength limit. Such behavior results from the double negativity of the effective constitutive parameters, bulk modulus and mass density, in a limited frequency range. This acoustic metamaterial is composed of balloon-contained water spheres (BLWSs) and hard rubber-coated lead spheres (HRLSs) embedded in epoxy matrix. Dispersion relation calculations by using the effective parameters, shows a negative dispersion band related to the negative refractive index for longitudinal waves. The physical realization of such metamaterial for acoustic waves could lead to many unusual applications as in the case of electromagnetism, including the manufacturing of an acoustic cloaking device.