Cloaking of an acoustic sensor using scattering cancelation

Abstract

Acoustic scattering cancelation (SC) is an approach enabling the elimination of the scattered field from an object, thereby cloaking it, without restricting the incident wave from interacting with the object. This aspect of an SC cloak lends itself well to applications in which one wishes to extract energy from the incident field with minimal scattering, such as for sensing and noise control. In this work, an acoustic cloak designed based on the scattering cancelation method, and made of two effective fluid layers, is applied to the case of an acoustic sensor consisting of a hollow piezoelectric shell with mechanical absorption, providing a 20–50 dB reduction in the scattering strength. The cloak is shown to increase the range of frequencies over which there is nearly perfect phase fidelity between the acoustic signal and the voltage generated by the sensor, while remaining within the physical bounds of a passive absorber. The feasibility of achieving the necessary fluid layer properties is demonstrated using sonic crystals with the use of readily available acoustic materials. [Work supported by the US ONR and Spanish MINECO.]