音響メタマテリアルを用いた音波偏向手段の検討

抄録

In this study, we made the acoustic meta-materials for changing sound transmission property in semi-finite field. By arranging apparent density of the materials distributed over the aperture through which the wave penetrated perpendicularly, the sound transmission path could be inclined from the nominal axis of the wave front. At first, we devised several patterns of the acoustic meta-materials. The first pattern is formed as a series of slits. The second pattern is a two-dimensional array of square props. The third pattern is an array of three-layered slits. The wave propagation analysis in two-dimensional free field incorporating the material was performed using the finite element method. We found from the simulation that all of three types affected the sound deflection. We then conducted sound field measurements for the acoustic meta-materials. Consistent results have been obtained in experiments. However, it was found that the equivalent sound velocity distribution is not linearly distributed in the width direction of the acoustic meta-materials, and the wave front of the interference sound wave after the acoustic meta-materials transmission is disturbed. Therefore, we devised a new acoustic meta-material in which the equivalent sound velocity distribution changes continuously and linearly. By performing simulation using this acoustic meta-material, we could confirm the deflection of the regular wavefront.