Loading video... VIDEO: Square norm of sound pressure in water around a designed acoustic cloak during topology optimization. view more Credit: GARUDA FUJII, INSTITUTE OF ENGINEERING, SHINSHU UNIVERSITY, JAPAN Until now, it was only possible to optimize an acoustic cloaking structure for the air-environment. However, with this latest research, Acoustic cloak designed by topology optimization for acoustic-elastic coupled systems, published in the latest Applied Physics Letters, it is possible to design an acoustic cloak for underwater environments. In the conventional topology optimization of acoustic cloaking, the design method was based on an analysis that approximated an elastic body in the air as a rigid body. However, since the approximation holds only for materials that are sufficiently stiff and dense such as metal in the air, there were few material options other than metal. Moreover, it was impossible to design an acoustic cloak in water by the approximation method.