Damage detection and location is a problem that is encountered in a broad range of fields, including aircraft and spacecraft integrity, manufacturing and production reliability, structural health monitoring, and infrastructural damage due to aging as well as in response to large earthquakes. A new generation of mechanical damage diagnostics and imaging methods has been developed over the last decade. Nonlinear elastic methods, known collectively as nonlinear elastic wave spectroscopy (NEWS), can be applied to distinguish whether or not a crack exists in an opaque solid. Imaging methods are under development that combine NEWS with the time-reversal mirror (TRM).

Time reversal is a remarkable technique for producing large sound amplitudes at the original source location, or locating an anomaly in a solid that scatters waves. Thus, time reversal provides the means to locate an elastic anomaly, and nonlinear elasticity allows one to learn about its nature. The combination of the two techniques is known as time-reverse nonlinear elastic wave spectroscopy (TR NEWS).