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.
Highlights
In 1968, Veselago [1] proposed the concept of metamaterials possessing properties not found in typical materials in EM waves
The material material properties of the metamaterial used in the structure of the cloak were based on transformation properties of the metamaterial used in the structure of the cloak were based on transformation acoustics
The field pattern the field pattern results showed the cloak availability at the 1000 Hz design frequency of the results showed the cloak availability at the 1000 Hz design frequency of the meta-composite structure, meta‐composite structure, and the visibility results verified the effectiveness of the cloak shell
Summary
In 1968, Veselago [1] proposed the concept of metamaterials possessing properties not found in typical materials in EM waves. In 2007, Cummer and Schurig [8] used the exact equivalence of acoustics and EM waves in the construction of two-dimensional (2D) acoustic cloaks. They paved the way for the application of coordinate transformation techniques to provide cloaks for acoustic waves. In 2013, Chen et al [10] expanded the strategy of transformation acoustics from simple cylindrical shapes to general coordinate systems. This was achieved by overcoming the difficulties involved in impedance matching along the boundary of the
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