Acoustic Band Gap Materials

Abstract

In recent years, there has been a growing interest in the propagation of acoustic and elastic waves in periodic composite materials. Such materials are the acoustic or elastic analogue of photonic crystals, and in both cases, much of the interest has focused on theoretical and experimental studies of spectral gaps due to the periodicity of the underlying structure [1–11]. For sound, these are often referred to as phononic band gaps, by analogy with photonic band gaps for light and electronic band gaps for metals. Motivation for studying materials with phononic band gaps is driven in part from potential applications, examples being their role in sound filters, transducer design and acoustic mirrors. Of possibly greater interest from the fundamental scientific perspective is the rich physics of acoustic and elastic systems, where scattering contrast is affected by both density and velocity differences, and the waves can have a mixed longitudinal and transverse vector character, leading to the possibility of novel propagation phenomena. These features of phononic band gap materials may also make them interesting candidates for studies of wave localization.