Effect of Thickness of Epoxy Encapsulation Material on the Performance of Underwater Tonpilz Transducer

Electro-acoustic transducers capable of converting electric energy to acoustic energy and vice versa are critical elements in Sonar systems. Among different types of electro-acoustic transducers Tonpilz transducer is widely used due to their ability to operate in both transmitting and receiving mode and generation of directional high acoustic power. Typically tonpilz transducers are encapsulated by a visco-elastic material when used in underwater applications. The primary function of encapsulation material is to protect the transducer from water ingression and physical damage without affecting significantly the acoustic transmission and reception properties, thereby influencing efficiency and reliability of transducers. In view of these, epoxy elastomers are widely used for encapsulation of tonpilz transducers. The term epoxy, epoxy resin or epoxide refers to a broad group of reactive compounds that are characterized by the presence of an oxirane or epoxy ring. For applicability and suitability of epoxy for a particular underwater application, its compositions and encapsulation thickness are the crucial parameters. In this paper the effect of the variation of encapsulation thickness of epoxy on the transmitting voltage response (TVR) and free field sensitivity (FFS) of a tonpilz transducer designed for underwater applications are presented.