What are microphones?

There is one simple explanation and several more complex explanations.

The simple explanation is that a microphone is a device used to produce electrical signal from an auditory signal. Some auditory signal finds its way into the microphone, and it causes a physical response, and that causes an electrical signal to be transferred to the audio board.

The more complex explanations can be split into two main parts for this book: Condenser microphones, and dynamic microphones. Condenser microphones need an electrical signal to be sent to the microphone (often this is called phantom power at +48V, though there are many different possibilities). The diaphragm, the bit that responds to the physical auditory signal, is an conductive membrane that will move back and forth to complete a circuit. Importantly there is a break in the circuitry, and a resistor completing it slightly before the diaphragm. The resistor is slightly less resistance than the resistance cause by the break in the circuit, so while a not significant amount of pressure is on the diaphragm, the electrical signal is going through the resistor and, hopefully, sends back a clean blank signal to the board. However, when an auditory signal puts pressure on the diaphragm, it completes the circuit and sends back a signal that is clean, crisp, and clear (as shown below).

A dynamic microphone on the other hand produces an electrical signal. A dynamic microphone’s diaphragm is not conductive, but rather attached to either a copper coil, or a magnet. The goal of the diaphragm on a dynamic microphone is to move a magnet and coil back and forth across each other. The movement of these two parts against each other creates an electrical signal that is sent down the cable back to the audio console. This explains why dynamic microphones tend to be less sensitive, and tend to need more gain in order to get the same volume as it would from a condenser microphone — the same pressure is moving far more mass than just the diaphragm.