Ultrasonics | physics | Britannica
Transducers. An ultrasonic transducer is a device used to convert some other type of energy into an ultrasonic vibration. There are several basic types, classified by the energy source and by the medium into which the waves are being generated. Mechanical devices include gasdriven, or pneumatic, transducers such as whistles as well as liquiddriven transducers such as hydrodynamic oscillators ...