recording

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Any of a variety of techniques used to capture, store, and reproduce music, speech, and other information carried by sound waves. A microphone first converts the sound waves into an electrical signal that varies in proportion to the loudness of the sound. The signal can be stored in digital or analogue form, or on magnetic tape.

Analogue recording
In an analogue recording, the pattern of the signal is copied into another form. In a vinyl gramophone record, for example, a continuous spiral groove is cut into a plastic disc by a vibrating needle. The recording is replayed by a stylus that follows the track of the groove, and so reproduces the vibrations that are amplified and turned back into sound. In a magnetic tape recording, the signal is recorded as a pattern of magnetization on a plastic tape coated with a magnetic powder. When the tape is played back, the magnetic patterns create an electrical signal that, as with the gramophone record, is used to recreate the original sound. All analogue recording techniques suffer from background noise and the quality of reproduction gradually degrades as the format changes and the disc or tape wears out.

Digital recording
In digital recording, the signals picked up by the microphone are converted into a stream of numbers that can then be stored in several ways. The most well-known of these is the compact disc, in which numbers are coded as a string of tiny pits pressed into a 12 cm/4.7 in plastic disk. When the recording is played back, using a laser, the exact values are retrieved and converted into a varying electrical signal and then back into sound. Digital recording is relatively free from noise and interference and gives a very high quality of reproduction. It is also suitable for storing information to be processed by computers.

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