Active control approach to temporal acoustic cloaking

Abstract

We propose a realization of a transformation-based acoustic temporal cloak using an active closed-loop control approach to an equivalent electromagnetic problem. Unlike the more common spatial cloaks, the goal of which is hiding fixed objects from detection, the goal of the temporal cloak is hiding the occurrence of events during a finite period of time. In electromagnetic systems, in which events represent, for example, leakage of signals from transmission lines or optical fibers, temporal cloaking solutions usually rely on nonlinear phenomena related to the fibers properties or on modulating the properties of the propagation medium itself. In particular, the transformation-based solution requires modulating the constitutive parameters of the medium in both space and time. In acoustic systems, an event may represent an object crossing a propagation channel and temporarily blocking it. Our control approach is fully linear, where the required change in the medium parameters is programmed into the controllers and created by external actuators in real-time. This cloaking system keeps the physical medium unchanged and enables re-programing of the cloaking parameters upon request. We demonstrate our solution in a simulation of a one-dimensional water channel.