Sound as Electricity

We use microphones to convert sound in air into and electrical signal.

These electrical signals can be amplified (increasing the voltage and current) so that it can driver a loudspeaker.

Microphones come in two types : electro-mehcanical and piezo-electric.

Electro-mechanical microphones use a small diaphram attached to a coil of wires suspended in a magnetc field. When the vibrations in the air cause cause the diaphram to vibrate, the movement of the coil of wire in the magnetic field generates a small electric current.

Piezo-electric microphones harness the physical properties of certain types of crystal which generate a very small electrical signal when placed under stress. In this case, the stress is placed on the crystal by the vibration of air molecules.

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