Microphone

It works like a loudspeaker in reverse. Sound makes a diaphragm vibrate and moves a small coil in a magnetic field. That movement creates a tiny changing voltage: the sound becomes an electrical signal.

Sound supplies the energy that creates the signal, so this microphone needs no external power. A preamplifier boosts its weak signal for the next circuit.

At SparkVille’s radio station, a microphone turns the announcer’s voice into a signal for the broadcast circuit.