Characteristics of Acoustic Metamaterials

Abstract

The term “metamaterials” refers to artificial constructs whose characteristics are determined by the collective manifestations of local units. When such constructs are designed for acoustic wave manipulation, they are referred to as acoustic metamaterials. Acoustic metamaterials allow controlled wave propagation that is often inconceivable through chemically developed bulk materials. This means that the wave propagation in acoustic metamaterials goes beyond the mass-density characteristics of the material resulting in targeted acoustic outcomes. The unique characteristics of acoustic metamaterials have opened a new direction in the development of effective solutions for a range of applications, including but not limited to low-frequency sound insulation, acoustic cloaking, sound focusing, biomedical acoustics, and passive destructive interference. The overall characteristic of an acoustic metamaterial depends on the type of sound manipulation being targeted. This article introduces the characteristics associated with some of the most promising acoustic metamaterials from passive to active. An effort is placed to highlighting both the underlying principles and the physical prototypes that were evaluated.