Introduction to Sonar Transducer Design

2Mechanical/Acoustical Equivalent Circuits

This chapter introduces the concept of a mechanical and acoustical equivalent circuit. It is appropriate to introduce this subject prior to the introduction of waves in solid media (Chapter 3) as many of the concepts described here are similar to, or form a fundamental foundation for, the more difficult concepts of Chapter 3. In a sense, this chapter forms a bridge between the acoustic concepts of Chapter 1 and the waves in solids concepts of Chapter 3. The fact that this chapter represents a bridge between two subject matters should not diminish the importance of the material described herein. Many of the equivalent circuit models that are developed in Chapter 4 to describe projectors and Chapter 5 to describe receivers and hydrophones are based on the basic concepts developed in this chapter.

Equivalent circuits are generally divided up into three types: electrical, mechanical, and acoustical. With electrical equivalent circuits, we assign lumped parameters to represent resistance, inductance, and capacitance. We can combine these in an equivalent circuit to represent the electrical portion of our system.

However, we may not be as familiar with the mechanical or acoustical equivalent circuits. In analyzing mechanical systems, we develop electrical analogs of mechanical or acoustical elements. These analogs represent the mechanical equivalent of resistance, inductance, or capacitance. These elements comprise an equivalent circuit, ...