Broadband transparent periodic acoustic structures

Abstract

The creation of acoustically transparent materials is of interest for enhanced energy focusing in metamaterial lenses, vibration isolation and structure concealment in underwater environments. It has previously been shown that metal pentamode metamaterials may provide water like behavior yet retain enough shear to provide structural stability. This is achieved through a periodic lattice with sub-wavelength cells. The current talk presents a study on the simulated and experimental behavior of other structural materials that operate similar to pentamode composites, which exhibit transparency in underwater conditions. Specifically, we examine a two-dimensional design composed of a honeycomb arrangement of fluid inclusions in a solid polymer background. Materials, designs and simulations are supported through both band structure calculations and transmission modeling of finite slabs of the device. Experiments are performed in a water-filled test tank and broad frequency behavior is examined. Issues such as boundary coupling and omni-directionality are discussed. © 2013 Acoustical Society of America.