Broadband Acoustic Cloak for Ultrasound Waves

TL;DR

This paper reports the first practical, broadband, low-loss underwater acoustic cloak for ultrasound using a metamaterial network of circuit elements, demonstrating effective wave bending and reduced scattering over a wide frequency range.

Contribution

It introduces a scalable, non-resonant metamaterial design for broadband acoustic cloaking, advancing practical underwater invisibility technology.

Findings

Effective ultrasound wave bending around the object

Broadband cloaking from 52 to 64 kHz

Low loss (~6dB/m) performance

Abstract

Invisibility devices based on coordinate transformation have opened up a new field of considerable interest. Such a device is proposed to render the hidden object undetectable under the flow of light or sound, by guiding and controlling the wave path through an engineered space surrounding the object. We present here the first practical realization of a low-loss and broadband acoustic cloak for underwater ultrasound. This metamaterial cloak is constructed with a network of acoustic circuit elements, namely serial inductors and shunt capacitors. Our experiment clearly shows that the acoustic cloak can effectively bend the ultrasound waves around the hidden object, with reduced scattering and shadow. Due to the non-resonant nature of the building elements, this low loss (~6dB/m) cylindrical cloak exhibits excellent invisibility over a broad frequency range from 52 to 64 kHz in the measurements. The low visibility of the cloaked object for underwater ultrasound shed a light on the fundamental understanding of manipulation, storage and control of acoustic waves. Furthermore, our experimental study indicates that this design approach should be scalable to different acoustic frequencies and offers the possibility for a variety of devices based on coordinate transformation.