Active cloaking with transducers

In an ideal acoustical cloaking operation plane waves from a sonar source arrive at an object, emerge from the opposite side, reflect or scatter from other objects and return back to the sonar source as if there were no object. With passive cloaking materials surrounding the object the acoustic waves appear to bend around the object as if the object were transparent and not there. Efforts to ultimately develop such passive metamaterials for cloaking objects, such as, AUV´s and UUV´s are underway. It has, however, been pointed out that this form of passive cloaking could cover an object in a way that shields the object from using its own acoustic sonar means for detecting the source, unless the cloaking can be turned off. We address this issue by presenting an active cloaking transducer system which effectively cloaks an object and makes it acoustically invisible, but yet can also be used as an acoustic sonar system. Equivalent circuits and finite element models are presented and used to demonstrate this active transducer cloaking system.