In the preceding parts, we showed that electromagnetic and electrostatic transducers require two different types of analogy if they are to be represented by the networks shown in
Table 3.1. A further need for two types of analogy is apparent from the standpoint of ease of drawing an analogous circuit by inspection. The admittance type of analogy is better for mechanical systems and the impedance type for acoustic systems. The circuits we shall use, however, will frequently contain electrical, mechanical, and acoustical elements. Because analogies cannot be mixed in a given circuit, we must have a simple means for converting from one to the other.
To facilitate the conversion from one type of analogy to another, a method that we shall dub the “dot” method is used
[9]. Assume that we have the admittance-type analog of
Fig. 3.17 and that we wish to convert it to an impedance-type analog. The procedure is as follows (see
Fig. 3.41):
After completing the formation of an analogous circuit, it is always profitable to ask concerning each element. If this element becomes very small or very large, does the circuit behave in the same way the device itself would behave? If the circuit behaves properly in the extremes, it is probably correct.