Those changes are translated into electrical signals and transmitted. Carbon microphones are the simplest and least expensive. In carbon mics, the movement of a diaphragm is transmitted to carbon granules inside a small container connected to the diaphragm. As sound waves strike the diaphragm, the carbon granules move. The resulting fluctuations in the current running through the system are then amplified and transmitted.
Dynamic microphones form a middle ground in terms of cost and sophistication.
In these microphones, a coil of wire is connected to the diaphragm, which is in a strong magnetic field. Sound waves moving the diaphragm and coil generate an electrical signal that varies in voltage with the amplitude and frequency of the sound waves. Because dynamic mics use a magnetic field, they are susceptible to electromagnetic interference, which can garble transmissions. Dynamic mics for aviation use are carefully shielded to minimize the chances of such interference. Much is made of noise canceling microphones and with good reason the less background noise cluttering up your transmissions, the better.