KNOWLEDGE

What’s the difference between different microphone designs, and how do they work?

All microphones work in a similar way. They have a diaphragm (or a ribbon) that moves in response to changes in air pressure due to sound waves impinging on the diaphragm – similarly to how the diaphragm or ‘eardrum’ in the human ear responds to sound. The movement of this diaphragm, or ribbon, then produces a changing voltage, with a positive value (or amplitude) when the diaphragm moves one way and a negative value (or amplitude) when the diaphragm moves the opposite way. There are three main types of microphone to choose from – dynamic, ribbon, and condenser.

DYNAMIC MICS

With a so-called ‘dynamic’ microphone (the word ‘dynamic’ means changing or moving), a small coil of wire, positioned within the magnetic field of a permanent magnet, is attached to the diaphragm. When a sound wave enters the microphone, the diaphragm vibrates back and forth in an analogous way to the movements of the sound wave. When a wire moves in a magnetic field, a current is induced in it. So, the pressure of the sound wave vibrates the diaphragm, which in turn moves the coil in the magnetic field, inducing the electrical signal in the wire, which is then passed to the microphone cable (sometimes through a step-up transformer to increase the voltage).