Underwater acoustic ground cloak development and demonstration

Abstract

Acoustic ground cloaks, which conceal an object on a rigid surface, utilize a linear coordinate transformation to map the flat surface to a triangular void by compressing space into two triangular cloaking regions consisting of a homogeneous anisotropic acoustic metamaterial. Transformation acoustics allows for the realization of a coordinate transformation through a reinterpretation of the scale factors as a new material in the original coordinate system. An underwater acoustic ground cloak was constructed from perforated steel plates and experimentally tested to conceal an object on a pressure release surface. The perforated plate acoustic ground cloak successfully cloaked the scattered object. There was excellent agreement between the phase of the surface reflection and cloak reflection with a small amplitude difference. Above 15 [kHz], the cloaking performance decreased as the effective material parameters of the perforated plate metamaterial deviated from the required material parameters.

Cloaking and Holography Experiments Using Immersive Boundary Conditions

“…Acoustic cloaking is one of the most widely studied innovations using metamaterials. Numerous invisibility devices have been proposed, with potential applications in the fields of noise reduction, architectural acoustics, civil engineering, acoustic imaging, and underwater acoustics [10][11][12][13][14].…”