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Sound recording

Methods and media for sound recording are varied and have undergone significant changes between the first time sound was actually recorded for later playback until now.

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Mechanical Recording

The first devices for recording sound were mechanical in nature.

In 1796 a Swiss watchmaker named Antoine Favre described his idea for what we now call the cylinder musical box[?]. This can be considered an early method of recording a melody, although it does not record an arbitrary sound and does not record automatically. "Playback" however is automatic.

The Player piano was a device that could playback a piano performance which had earlier been mechanically recorded onto a piano roll.

The first recording of sound waves

Leon Scott[?] invented the 'phonoautograph', the first device to record arbitrary sound in 1857. It used a membrane (which vibrated in response to sound) attched to a pen, which traced a line roughly corrisponding to the sound wave form on to a moving roll of paper. Although able to record sound, the phonoautograph was unable to play back the recording; it was of little use other than as a laboratory curiousity.

The Phonograph and the Gramophone

The phonograph built expanding on the principles of the phonoautograph. Invented by Thomas Edison in 1877, the phonograph was a device with a cylinder covered with a soft material such as tinfoil[?], lead, or wax on which a stylus drew grooves. The depth of the grooves made by the stylus corresponded to change in air pressure created by the original sound. The recording could be played back by tracing a needle through the groove and amplifying, through mechanical means, the resulting vibrations. A disadvantage of the early phonographs was the difficulty of reproducing the phonograph cylinders in mass production.

This changed with the advent of the gramophone (phonograph in American English), which was patented by Emile Berliner in 1887. The gramophone imprinted grooves on a disk record. Instead of recording the varying the depth of the groove (vertically), as with the phonograph, the vibration of the recording stylus was across the width of the track ( horizontally). The depth of the groove remained constant.

In audio fidelity terms the disc record was inherently neither better than or worse than than the phonograph cylinder, but the disc records were easier and cheaper to mass produce. Reproduction of these disks was relatively simple by pressing a master image on a plate of shellac. The speed at with the disks were spun around was eventually standardized at 78 rotations per minute (rpm). Later innovations allowed lower rotations: 45 and 33 rpm, and the material was changed to vinyl. (see analogue disc record for a more detailed discussion)

Both phonograph cylinders and gramophone discs were played on mechanical devices most commonly hand wound with a clockwork motor. The sound was amplified by a cone that was attached to the diaphragm. The disc record largely surplanted the competing cylinder record by the late 1910s.

The advent of electrical recording in 1924, and electrical playback in 1925 drastically improved the quality of the recording process of disc records.

Magnetic Recording

Around 1900 V. Poulsen introduced a method of recording sound to magnetic wire. Tape replaced wire as the recording medium in 1924 thanks to German engineer C. Stille. An electrical signal, which is analogous to the sound that is to be recorded, is fed to the record head of a tape recorder. The tape is magnetized as it moves with a constant speed past a recording head. A playback head can then pick up the changes in magnetic field from the tape and convert it into an electrical signal.

On Christmas day 1932 the British Broadcasting Corporation first used a tape recorder for their broadcasts.

A tape allows multiple tracks in parallel to each other. This allowed for stereo sound (2 tracks), and quadrophonic sound (4 tracks). In a professional setting today, such as a studio, audio engineers may use 24 tracks or more for their recordings, one (or more) tracks for every instrument played.

Until 1963, when Philips introduced the Compact audio cassette, tape recording had been largely on open reel tape recorders. The Compact audio cassette added much needed convenience to the tape recording format. Although it was much lower in quality than open reel formats.

In 1965 Dolby Laboatories invented a noise reduction system for analogue tape. This improved the perceived level of tape hiss, which is inherant to the medium. Originally this system, known as Dolby A, was only used in professional recording. Dolby, however went on to develop more advanced noise reduction techniques for both professional and consumer formats, including the Compact audio cassette.

Other magnetic recording formats:

Recording on Film

To avoid synchronization problems, on sound films the sound track is recorded optically on to the side of the strip of motion picture film.

The first attempts to record sound to an optical medium occurred around 1900. In 1906 Lauste applied for a patent to record sound on film, but was ahead of his time. In 1923 de Forest applied for a patent to record to film. In 1927 the sound film The Jazz Singer was released; while not the first, it made a tremendous hit and made the public and the film industry realize that sound film was more than a mere novelty.

There are two methods for recording on film. Variable density recording uses changes in the darkness of the soundtrack side of the film to represent the soundwave. Variable width recording uses changes in the width of a dark strip to represent the soundwave.

In both cases light that is sent through the part of the film that corresponds to the soundtrack changes in intensity, proportional to the original sound, and that light is not projected on the screen but converted into an electrical signal by a light sensitive device.

Digital Recording

Early digital audio recorders use a device to make it possible to record digital audio on a U-matic[?] video machine. This was followed by digital open reel multitrack recorders. With the improvement in digital storage technology, a variety of recording media is used to record digital audio today.

Digital Audio Tape (DAT) recorded the raw audio sampled at 48 kHz with a resolution of 16 bits. DAT is still used in studios. A failed digital tape recording system is the Digital Compact Cassette[?] (DCC).

In the consumer market, tapes and gramophones were largely displaced by the compact disc (CD) and a lesser extent the minidisc. These recording media are fully digital and require complex electronics to play back.

Sound files can be stored on any computer storage medium.

Mention hard disk recorder


The earliest methods of recording sound involved the live recording of the performance directly to the recording medium. This was an entirely mechanical process, often called "Acoustical recording". The sound of the performers was captured by a diaphragm with the cutting needle connect to it. The needle made the grooves in the recording medium.

To make this process as efficient as possible the diaphragm was located at the apex of a cone and the performer(s) would crowd around the other end. If a performer was too loud then they would need to move back from the mouth of the cone to avoid drowning out the other performers. As a result of this, in early Jazz recordings a block of wood was used in place of the bass drum.

The advent of electrical recording made it possible to use microphones to capture the sound of the performance. The leading record labels switched to the electric microphone process in 1925, and most other record companies followed their lead by the end of the decade. Electrical recording incresed the flexibity and sound quality. However once the performance was still cut to to the recording medium, so if a mistake was made the recording was useless.

Electrical recording made it possible to record one part to disc and then play that back while playing another part, recording both parts to a second disc. This is called over-dubbing. The first commercially issued records using over-dubbing were released by the Victor Talking Machine Company in the late 1920s. However overdubbing was of limited use until the advent of analogue audio tape. Use of tape overdubbing was pioneered by Les Paul and is called 'sound on sound' recording. In this way performances could be built up over time.

The analogue tape recorder made it possible to erase or record over a previous recording so that mistakes could be fixed. Another advantage of recording on tape is the ability to cut the tape and join it back together. This allows the recording to be edited. Pieces of the recording can be removed, or rearranged. See Audio editing, Audio mixing

Mention Multitrack Recording here.

The advent of electronic instruments (especially keyboards and synthesisers), effects and other instruments has lead to the importance of MIDI in recording. For example, using MIDI timecode, it is possible to have different equipment 'trigger' without direct human intervention at the time of recording.

In more recent times, computers (digital audio workstation[?]) have found an increasing role in the recording studio, as their use eases the tasks of cutting and looping, as well as allowing for instantaneous changes, such as duplication of parts, the addition of affects and the rearranging of parts of the recording.

See also: binaural recording, microphone technique

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