ABSTRACT
The effects discussed in this chapter are twofold in nature. One group (multiple scattering, time reversal, and air-coupled ultrasonics) are part of traditional ultrasonics, but recent advances have given them topical interest. The other group (picosecond ultrasonics and resonant ultrasound spectroscopy) are relatively new techniques that promise to enlarge the scope of ultrasonic studies of materials and devices. Their inclusion here is justified by the high probability that they will be of lasting interest in future work on ultrasonics.
