The experimental realization of an acoustic cloak in air with a meta-composite shell

Abstract

Anisotropic cloak shells can be used for the spatial transformation of a space to alter the propagation of acoustic waves by redirecting them along a pre-determined path. This paper outlines the design, fabrication, and experimental analysis of a circular acoustic cloak shell made of meta-composite material for in-air applications. Based on the three-dimensional coordinate transformation, we first designed an anisotropic circle meta-composite cloak shell according to its impedance values. The cloak shell comprises various layered structures with cavities and tubes, respectively, providing acoustic mass and compliance for the provision of anisotropic material properties. Secondly, we conducted numerical and experimental analyses under practice working conditions to demonstrate the efficacy of the acoustic cloak. The structure of the cloak shell, fabricated by three-dimensional printing (3D printing), is experimentally evaluated in a semi-anechoic room with a free-field environment. The simulation and experimental results demonstrate the acoustic cloaking effects in the scattering far field. Besides the scattering field, the sound field measurement results obtained with the region enclosed by the shell also shows the abilities of the cloak shell in altering the direction of wave propagation along a pre-determined path in air.