Pressure-invariant non-reflective and highly dissipative acoustic metamaterials

Abstract

Metamaterials have shown great potential to transform the design of acoustic components in many applications. Many composites with extreme properties have been envisioned, designed, fabricated, and experimentally verified. The next step involves testing such composites in realistic application environments. Oceans are one such environment in which the mechanical effects of water pressure and flow become important factors in any acoustic design, particularly for soft dissipative shells. We have designed a layered metamaterial composite that not only shows very high dissipation but also matches the acoustic impedance of water. Furthermore, we have experimentally verified that the relevant properties of the constituents of this layered design do not change under pressure levels that exist down to significant depths. We are in the process of fabricating this composite to test its acoustic properties under pressure. The metamaterial composites lend themselves naturally to multi-component designs, examples of which as well as gradient media will be presented. Some potential novel applications of gradient and layered components will be discussed.