Topic Menu

Cyber-chess a chess instruction site

Microphone

A microphone is a transducer (a device that changes one energy form into another) that converts sound energy into electrical energy.

Microphones use electromagnetic induction to induce a current in a coil of wire - the pressure variations of sound waves are turned into electrical impulses.

The moving-coil microphone

The sound wave signal consists of air pressure variations. These sound waves cause the flexible diaphragm to vibrate in time with the air pressure vibrations.

The coil is positioned within the magnetic field of a permanent magnet, so as it moves it 'cuts through the flux lines' of the magnetic field.

This induces a potential difference in the coil by electromagnetic incuction - the generator effect.

The coil is part of a complete circuit, so the induced potential difference causes a current to flow in the output circuit.

The changing size and direction of the induced current matches the vibrations of the coil.

So the electrical signals generated match the pressure variations in the sound waves.