Sound recording

Sound recording is an electrical or mechanical inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are 'analogue recording' and 'digital recording'.

Acoustic analogue recording is achieved by a small microphone diaphragm that can detect changes in atmospheric pressure (acoustic sound waves) and record them as a graphic representation of the sound waves on a medium such as a phonograph (in which a stylus senses grooves on a record). In magnetic tape recording, the sound waves vibrate the microphone diaphragm and are converted into a varying electric current, then converted to a varying magnetic field by an electromagnet. This process makes a representation of the sound as magnetised areas on a plastic tape with a magnetic coating on it.

Analogue sound reproduction is the reverse process, with a larger loudspeaker diaphragm causing changes to atmospheric pressure to form acoustic sound waves. Electronically generated sound waves may also be recorded directly from devices such as an electric guitar pickup or a synthesiser, without the use of acoustics in the recording process, other than the need for musicians to hear how well they are playing during recording sessions.

Digital recording converts the analogue sound signal picked up by the microphone to a digital form by a process of digitisation, allowing it to be stored and transmitted by a wider variety of media. Digital recording stores audio as a series of binary numbers representing samples of the amplitude of the audio signal at equal time intervals, at a sample rate so fast that the human ear perceives the result as continuous sound.

Digital recordings are considered higher quality than analogue recordings - not necessarily because they have higher fidelity (wider frequency response or dynamic range), but because the digital format can prevent much loss of quality found in analogue recording due to noise and electromagnetic interference in playback, and mechanical deterioration or damage to the storage medium. A digital audio signal must be reconverted to analogue form during playback before it is applied to a loudspeaker or earphones.

Related methods include: Sound generation.

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