Effective metamaterial properties for non-local active acoustic media

Abstract

Acoustic metamaterials are generally composed of complex arrays of subwavelength unit cells that can be cumbersome to analyze and simulate. Consequently, it is common practice to approximate metamaterials as homogeneous media with unique material properties, most commonly negative or near-zero density, negative or near-zero bulk modulus, or both negative or near-zero density and bulk modulus. In addition to easing the computational burden associated with complex metamaterial structures, effective material properties can provide deeper understanding of system behavior, providing additional insight and tools in the development of acoustic metamaterials. Here, we present a method for determining effective material properties for a non-local, active acoustic metamaterial. We contrast these properties with those typically associated with acoustic metamaterials and discuss how such properties are characteristic of a new class of acoustic metamaterials.