4.2.1 Microphone
A microphone converts sound in the air to an electrical signal. Sounds consist of pressure waves in (usually) the air, and to reproduce a particular sound it is necessary to reproduce the corresponding pattern of pressure waves. A microphone converts the pressure waves in the air to the same pattern of voltage waves on wire. If this pattern of voltage variation is applied to a loudspeaker, the speaker converts the electrical signal back to pressure waves in the air, reproducing the sound.