Piezoelectric Transducer Designs for Sonar Applications

An electroacoustic transducer is a device that converts acoustic energy (sound) into electrical energy (voltage or current) or vice versa. When the transducer is used to generate sound, it is called a projector, transmitter, or source. When it is used to detect sound, it is called a receiver. Furthermore, when the receiver is employed underwater, it is referred to as a hydrophone. An underwater sonar system consists of projectors, hydrophones, and associated electronics such as amplifiers and data acquisition systems. This chapter, however, will only cover the description and operational principles of the projector and hydrophone components. More specifically, the chapter will focus on piezoelectric ceramic-based transducer designs intended for underwater use that operate in the frequency band spanning from 1 kHz to 1MHz. This span covers weapons sonar (1–100kHz) and imaging sonar (100 kHz to 1MHz) applications. Section 11.2 describes the fundamental parameters and measurement techniques necessary to characterize transducers both in air and in water. The piezoelectric ceramic materials that are most commonly used in sonar transducers and their relevant materials properties are discussed in Sect. 11.3. The most common piezoelectric ceramic-based projector designs for sonar applications are described in Sect. 11.4, where they are grouped according to their operational frequency range. A single transducer cannot operate efficiently over the entire 1-kHz to 1-MHz frequency band – primarily due to impedance matching issues with the associated amplifiers. Consequently, a variety of transducer designs have been developed and optimized for different frequency ranges. The chapter concludes with hydrophone characterization, designs, and some performance results in Sect. 11.5.