Introduction to Sonar Transducer Design

5Sonar Hydrophones

In the last chapter, we talked about how a projector converts electrical energy to strain energy via the piezo‐electric activity of a piezo‐ceramic element. Then, when packaged appropriately, the strain energy is converted to acoustic energy. In this chapter, we discuss the reverse effect. A hydrophone converts acoustic energy to electrical energy. We will start with a description of the contributing components of noise, and mechanical, electrical, and acoustical signals that compete with the acoustic signal we desire to detect. Understanding the contributing elements of noise is critical in proper hydrophone design.

5.1 Elements of Sonar Hydrophone Design

We showed in the last chapter that a large volume of piezo‐ceramic material was important for obtaining power from an active transducer. However, in a hydrophone, the structure tends to be smaller and more delicate than in a projector. In a hydrophone, we want to obtain large deflections or strains under the action of an applied acoustic pressure field. These large deflections will subsequently produce a large output voltage via the piezo‐electric effect. The “lighter,” more compliant hydrophone structure enables large strains in the piezo‐ceramic material to occur under the action of acoustic pressure.

Another size constraint to hydrophones is the desired bandwidth of the hydrophone. Most users of hydrophones want lots of bandwidth. The resonance frequency of the hydrophone presents an upper limit to ...