Comparison measurements of homogenized material properties of underwater acoustic metamaterials

Abstract

A current area of research interest in acoustic metamaterials is the experimental validation of the effective properties computed using analytical and numerical models. This is generally done through an inverse measurement technique, by measuring the reflective and transmitted wave amplitudes and phases to calculate an effective impedance. When the background fluid used for this measurement is air, either an impedance tube or anechoic chamber can be utilized for these measurements. However, if the application of the metamaterial is for in-water applications, the measurement of these properties becomes much more difficult due to many complicating factors. Therefore, there has been little work obtaining homogenized, anisotropic material properties of underwater acoustic metamaterials. In this work, we present comparison of measurement methods of an acoustic metamaterial in an aqueous environment: a water-filled impedance tube and in a reverberant water tank. The metamaterial response will be predicted, and compared to the measurement in the impedance tube and reverberant tank. Additionally, trade-offs between the two experimental methods will be given.