Cloaking and Holography Experiments Using Immersive Boundary Conditions

We report the experimental realization of real-time and broadband acoustic cloaking and holography by manipulating wave fields through their boundary conditions. The method of immersive boundary conditions (IBCs) enables us to virtually replace part of a physical experiment with a virtual computational environment. By introducing a source surface enclosing the virtual environment and calculating the source strengths in real time, the wave field in the physical experiment can be controlled such that incoming waves are suppressed and transmissions through the arbitrary virtual domain are radiated in a desired manner. A one-dimensional experiment shows that scattering objects can be made undetectable without prior knowledge about the incident wave field. Moreover, virtual objects or media can be emulated where they are not present—even objects or media exhibiting properties that do not occur in nature. Our results provide useful insights into how to implement IBCs for dynamic cloaking and holography, suggesting that higher-dimensional experiments are feasible.