What Audio Is

Author: N.H. Crowhurst

In the early days of radio, the word "audio" was used to describe the part of a radio receiver (or transmitter) that amplifies the audio, or sound frequencies. After detecting (later called demodulating) the radio waves or carrier, the signal was rather feeble, hardly sufficient to be audible in the headphones, so an audio amplifier was used to make the feeble signal audible in comfort. A similar amplifier was needed at the transmitter to magnify the feeble microphone currents for modulation of the radio carrier.

Audio once meant the "sound" end of a radio receiver.

From those early beginnings, audio amplifiers have found more and more uses, and have improved in performance. Quite early, audio amplification was applied to the making and reproducing of phonograph records, giving us the first "electrical" reproduction. Since then, the methods developed have been used for many things: all kinds of control mechanisms for industry; sonar-type detection devices; vibration measuring equipment for aircraft and other types of development or research; and many of the "brain cells1* used in electronic computers, to name just a few.