ABSTRACT
Ultrasonic devices consist of transducers which are composed of these piezoelectric materials. The first ultrasonic transducer was a whistle developed by Galton, who was then investigating the threshold frequency of human hearing. Ultrasonic sound can be produced by transducers which operate either by the piezoelectric effector themagnetostrictive effect. Ultrasonic transducers are designed to convert either mechanical or electrical energy into high-frequency sound. These transducers are of three types: gas-driven, liquid-driven and electromechanical. Electromechanical transducers are of two types. These are either based on the piezoelectric or the magnetostrictive effect. The magnetostrictive materials transduce or convert magnetic energy to mechanical energy and vice versa. A piezoelectric transducer consists of piezoelectric crystal, electrical connections, backing materials, and front layers and casing. A single-crystal ultrasonic transducer consists of a thin layer of piezoelectric material sandwiched between epoxy, a glue-like backing material, and a number of layers of facing.
