Transducer is a device that converts one form of energy into another. Many transducers convert electric waves into mechanical vibrations—or vice versa. Loudspeakers, microphones, and phonograph pickup cartridges are all transducers. Sonar transducers send and receive sound waves in water. Ultrasonic transducers generate and detect vibrations above the frequency range of human hearing. They are used to cut hard materials, to clean delicate instruments, to drill oil wells, and to measure the level of liquids in the fuel tanks of space vehicles.
Transducers work in various ways. Some phonograph cartridges use piezoelectric materials, which produce a voltage when squeezed. Loudspeakers use moving coils that vibrate when current moves through them. The vibrations result from an interaction between the coils and powerful permanent magnets. Some ultrasonic transducers use magnetostrictive materials, which contract in a magnetic field.
See also Ultrasound (Ultrasound devices) ; Sonar .
