Abstract
Several kinds of interactions of ultrasound in semiconductors are reviewed. The subjects discussed are the effects of interaction with 1) thermal phonons, which produce temperature dependent attenuation; 2) free carriers, which may give attenuation or amplification; 3) electrons bound to shallow donors, giving rise to attenuation at low temperatures; and 4) other ultrasonic waves, which may give attenuation or amplification. An introduction to relaxation effects is included.