The microphone is the foundation for all voice communications, whether in the transmission or recording of sound. The device transforms acoustical energy or sound into electrical energy (a process called transduction) so it can be reproduced through a loudspeaker or recorded for later playback on a magnetic tape. In 1876, Alexander Graham Bell constructed what was probably the first crude microphone as a component for his telephone. It worked by using the vibrations produced by a sound wave to move a disk of metal, inducing a current in an adjoining magnet. The weak electrical current produced by the magnet was sent a distance over wires, where it generated pulses in a similar magnet, moving another disk of metal to reproduce the sound. But the current induced by Bell's device was too weak to produce anything more than a feeble response.

Both Emile Berliner and Thomas Alva Edison set about...