Exterior cloaking with active sources in two dimensional acoustics

TL;DR

This paper presents a method for two-dimensional acoustic cloaking using multiple active sources placed outside the target region, effectively canceling incident waves and rendering objects undetectable.

Contribution

It introduces a novel exterior cloaking technique employing multipolar sources based on Green's formula and Hankel functions, advancing acoustic cloaking methods.

Findings

Effective cloaking achieved with three or more active sources

Minimal scattered waves from cloaked objects

Method applicable to known incident waves

Abstract

We cloak a region from a known incident wave by surrounding the region with three or more devices that cancel out the field in the cloaked region without significantly radiating waves. Since very little waves reach scatterers within the cloaked region, the scattered field is small and the scatterers are for all practical purposes undetectable. The devices are multipolar point sources that can be determined from Green's formula and an addition theorem for Hankel functions. The cloaking devices are exterior to the cloaked region.