Improving acoustic cloak bandwidth using nonlinear coordinate transformations

Abstract

Acoustic cloaking has become a major focus of acoustic metamaterials researchers in the past few years. In order to achieve acceptable cloak performance, linear coordinate mapping has been so far implemented. This linear transformation has been reported to be effective for the case of rigid objects; however, the cloaking becomes less perfect and dependent on the solution domain when flexible objects are considered, where its permeable nature might induce considerable absorption of sound wave, which would bring less perfection to the cloak. In the current research, acoustic cloaking based on different nonlinear coordinate transformation is presented. A finite element model, developed through time harmonic analysis, is implemented to study the pressure field distribution using different nonlinear coordinate transformations. Such transformations have shown considerable improvement to the cloak performance when applied to flexible objects allowing for wider applicability bandwidth as well as for providing additional control of the shape of acoustic wave bending inside the cloak region.