Self-focusing of acoustical beam in solid by time-reversal processing

1 IntroductionTime reversal is a unique self-adaptive focusing technique, it can realize the acollsticalbeam focusing and ultrasonic testing in the inhomogeneous mediatl], and the inhomogeneityof the media always causes curve of sound ray, distortion of wavefront, aberrance and blur ofimage. It is difficult or impossible to know the acoustical inhomogeneity of the media, such asocean or interior of solid. The greatest advantage of TR is that it can realize the self-adaptivefocusing without pr…