Broadband acoustic lens design by reciprocity and optimization.

A broadband acoustic lens is designed based on the principle of reciprocity and gradient-based optimization. Acoustic reciprocity is used to define the pressure at the focal point due to a source located in a far-field and to relate the response by a configuration of scatterers for an incident plane wave. The pressure at the focal point is maximized by rearranging the scatterers and supplying the gradients of absolute pressure at the focal point with respect to scatterer positions. Numerical examples are given for clusters of cylindrical voids and sets of elastic thin shells in water.