This paper briefly reviews progress in research on specific applications of acoustic radiation during the past 50 years. Among the topics discussed are the following: underwater ultrasonic detectors, the ultrasonic interferometer, use of ultrasonics in the nondestructive testing of metals, acoustics delay lines, improvements in the materials used in ultrasonic transducers, surface wave devices, acoustic emission, use of ultrasonics in the study of internal friction and fatigue in metals, and the ultrasonic microscope.