Study on deflection of transmitting sound using acoustic metamaterials

Abstract

Acoustic metamaterials possess the artificially adjusted physical properties related to the propagation of waves, such as the density of the medium and volume modulus. The acoustic characteristic is governed by the structural shape rather than the physical properties of the material. In this study, we numerically investigated the deflection of transmitting sound by the acoustic metamaterials. Firstly, the equivalent sound velocity values necessary to achieve the designated deflection angle were given directly to the medium in each path without considering the metamaterial structure. The finite element analysis showed that three kinds of deflection angle, θ = 30°, 45°, and 60°, was successfully achieved at any frequency. Secondly, we devised an obstacle structure that generated a sound velocity gradient inside an acoustic metamaterial. It is found by the acoustic wave propagation analysis that the sound could be deflected in the frequency range from 500 Hz to 1.5 kHz. These investigations clearly showed that the sound waves can be deflected by using the acoustic metamaterials for the transmitted sound in two-dimensional space.