Audio microphones are designed for sound reception and recording applications that involve speech and music. Capacitance microphones include a thin surface and a rigid surface that are connected by wires to audio equipment. Sounds cause the air pressure to change, the surfaces to vibrate, and charges to move between the surfaces and the audio equipment. In electromagnetic microphones, changes in air pressure move a coil of wire. Since the wire is near a magnet, the electric charges in the coil move as a current.