We can begin with a picture, which shows a classic dynamic microphone, many of which were in very widespread use for many years, and you can still find lots of these in active service. In figure two, below, you'll see another dynamic microphone, a later model. The quality of the audio that these microphones deliver is excellent. Although different in external appearance, the internals of both of these microphones are quite similar.
The mic in this picture actually works like an electric generator, and as such is operates on the same principle as the typical generators in our power stations.
Below, in figure two, you'll see another, more modern type of dynamic microphone. These are manufactured today and you will find many of these in regular service wherever a relatively decent microphone is needed.
Both of these microphones that are represented here are fairly good, however there are many less-exacting applications where a cheap microphone is all that is necessary. Traditional telephones are a good example. Also the mics of the CB radios that were very much in vogue 30 years ago are another example. If a microphone only needs to reproduce speech, then the design criteria can be much less stringent that if the microphone is going to be used in professional recording situations.
We will start by looking at one of the earliest microphones, the so-called carbon microphone as it illustrates some of the basic principles which are common to practically all microphones today.
