Further developments

Further developments

Analog magnetic tape recording introduces noise, usually called "hiss", caused by the finite size of the magnetic particles in the tape. There is a direct tradeoff between noise and economics. Signal-to-noise ratio is increased at higher speeds and with wider tracks, decreased at lower speeds and with narrower tracks.
By the late 1960s, disk reproducing equipment became so good that audiophiles soon became aware that some of the noise audible on recordings was not surface noise or deficiencies in their equipment, but reproduced tape hiss. A few specialist companies started making "direct to disk" specialty recordings, made by feeding microphone signals directly to a disk cutter (after amplification and mixing). These recordings never became popular, but they dramatically demonstrated the magnitude and importance of the tape hiss problem.

audio cassette

Prior to 1963, when Philips introduced the Compact audio cassette, almost all tape recording had used the reel-to-reel (also called "open reel") format. Previous attempts package the tape in a convenient cassette that required no threading met with limited success; the most successful was 8-track cartridge used primarily in automobiles for playback only. The Philips Compact audio cassette added much needed convenience to the tape recording format and a decade or so later had begun to dominate the consumer market, although it was to remain lower in quality to open reel formats.
In the 1970s, advances in solid-state electronics made the design and marketing of more sophisticated analog circuitry economically feasible. This led to a number of attempts to reduce tape hiss through the use of various forms of volume compression and expansion, the most notable and commercially successful being several systems developed by Dolby Laboratories. These systems divided the frequency spectrum into multiple bands and applied volume compression/expansion independently to each band (Engineers now often use the term "compansion" to refer to this process). The Dolby systems were very successful at increasing the effective dynamic range and signal-to-noise ratio of analog audio recording; to all intents and purposes, audible tape hiss could be eliminated. The original Dolby A was only used in professional recording. Successors found use in both professional and consumer formats; Dolby B became almost universal for prerecorded music on compact cassette. Subsequent forms, including Dolby C, (and the short-lived Dolby S) were developed for home use.
In the 1980s, digital recording methods were introduced, and analog tape recording was gradually displaced, although it has not disappeared by any means. (Many professional studios, particularly those catering to big-budget clients, use analog recorders for multitracking and/or mixdown.) Digital audio tape never became important as a consumer recording medium partially because of legal complications arising from piracy fears on the part of the record companies. They had opposed magnetic tape recording when it first became available to consumers, but the technical difficulty of juggling recording levels, overload distortion, and residual tape hiss was sufficiently high that magnetic tape piracy never became an insurmountable commercial problem. With digital methods, copies of recordings could be exact, and piracy might have become a serious commercial problem. Digital tape is still used in professional situations and the DAT variant has found a home in computer data backup applications. Many professional and home recordists now use hard-disk-based systems for recording, burning the final mixes to recordable CDs (CD-R's).

Recording on film

Recording on 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 Lee de Forest applied for a patent to record to film; he also made a number of short experimental films, mostly of vaudeville performers. William Fox began releasing sound-on-film newsreels in 1926, the same year that Warner Brothers released Don Juan with music and sound effects recorded on discs, as well as series of short films with fully synchronized sound on discs. 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.
The Jazz Singer used a process called Vitaphone, a process that involved synchronizing the projected film to sound recorded on disk. It essentially amounted to playing a phonograph record, but one that was recorded with the best electronic technology of the time. Audiences used to acoustic phonographs and recordings would, in the theatre, have heard something resembling 1950s "high fidelity."
In the 1920s, when the first talkies came out, especially The Jazz Singer, theatre orchestra musicians were being replaced with mechanical music which cost the loss of many jobs.^[5] The American Federation of Musicians took out ads in newspapers, protesting the replacement of real musicians with mechanical playing devices, especially in theatres.^[6]
In the days of analog technology, however, no process involving a separate disk could hold synchronization precisely or reliably. Vitaphone was quickly supplanted by technologies which recorded a sound track optically directly onto the side of the strip of motion picture film. This was the dominant technology from the 1930s through the 1960s and is still in use as of 2004.
There are really two different types of synchronised film soundtrack, optical and magnetic. Optical sound tracks are visual renditions of sound wave forms and provide sound through a light beam and optical sensor within the projector. Magnetic sound tracks are essentially the same as used in conventional analog tape recording.
Magnetic soundtracks can be joined with the moving image but it creates an abrupt discontinuity because of the offset of the audio track relative to the picture. Whether optical or magnetic, the audio pickup must be located several inches ahead of the projection lamp, shutter and drive sprockets. There is usually a flywheel as well to smooth out the film motion to eliminate the flutter that would otherwise result from the pull-down mechanism. If you have films with a magnetic track, you should keep them away from strong magnetic sources, such as televisions. These can weaken or wipe the magnetic sound signal. Magnetic sound on an acetate base is also more prone to vinegar syndrome than a film with just the image.

A variable density soundtrack (left)and a bi-lateral variable area soundtrack (right)

For optical recording on film there are two methods utilized. Variable density recording uses changes in the darkness of the soundtrack side of the film to represent the soundwave. Variable area 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.
Optical soundtracks are prone to the same sorts of degradation that affect the picture: e.g. scratches, copying.
Unlike the film image that creates the illusion of continuity, sound tracks are continuous. This means that if you cut and splice film with a combined soundtrack, the image will cut cleanly but the sound track will probably produce a cracking sound. Fingerprints on the film may also produce cracking or interference.
Should you wish to use sound, there is of course no reason for employing either a magnetic or an optical sound track. You could use a secondary source to play alongside your images but bear in mind that precise syncing may be difficult. If you do use a secondary source, make sure you look after and document it precisely, as you would with the film it accompanies. You might also want to keep yourself informed for the future by looking into the technological information and history of the medium of this other source.
In the late 1950s the cinema industry, desperate to provide a theatre experience that would be overwhelmingly superior to television, introduced wide-screen processes such as Cinerama, Todd-AO, and CinemaScope. These processes at the same time introduced technical improvements in sound, generally involving the use of multitrack magnetic sound, recorded on an oxide stripe laminated onto the film. In subsequent decades, a gradual evolution occurred with more and more theatres installing various forms of magnetic-sound equipment.
In the 1990s, digital systems were introduced and began to prevail. Ironically, in many of them the sound recording is, as in Vitaphone, again recorded on a separate disk; but now, digital processes can achieve reliable and perfect synchronization.

Digital Recording

Digital Recording

The DAT or Digital Audio Tape

The first digital audio recorders were reel-to-reel decks introduced by companies such as Denon (1972), Soundstream (1979) and Mitsubishi. They used a digital technology known as PCM recording. Within a few years, however, many studios were using devices that encoded the digital audio data into a standard video signal, which was then recorded on a U-matic or other videotape recorder, using the rotating-head technology that was standard for video. A similar technology was used for a consumer format, Digital Audio Tape (DAT) which used rotating heads on a narrow tape contained in a cassette. DAT records at sampling rates of 48 kHz or 44.1 kHz, the latter being the same rate used on compact discs. Bit depth is 16 bits, also the same as compact discs. DAT was a failure in the consumer-audio field (too expensive, too finicky, and crippled by anti-copying regulations), but it became popular in studios (particularly home studios) and radio stations. A failed digital tape recording system was the Digital Compact Cassette (DCC).
Within a few years after the introduction of digital recording, multitrack recorders (using stationary heads) were being produced for use in professional studios. In the early 1990s, relatively low-priced multitrack digital recorders were introduced for use in home studios; they returned to recording on videotape. The most notable of this type of recorder is the ADAT. Developed by Alesis and first released in 1991, the ADAT machine is capable of recording 8 tracks of digital audio onto a single S-VHS video cassette. The ADAT machine is still a very common fixture in professional and home studios around the world.
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.
Digital sound files can be stored on any computer storage medium. The development of the MP3 audio file format, and legal issues involved in copying such files, has driven most of the innovation in music distribution since their introduction in the late 1990s.
As hard disk capacities and computer CPU speeds increased at the end of the 1990s, hard disk recording became more popular. At this writing (early 2005) hard disk recording takes two forms. One is the use of standard desktop or laptop computers, with adapters for encoding audio into two or many tracks of digital audio. These adapters can either be in-the-box soundcards or external devices, either connecting to in-box interface cards or connecting to the computer via USB or Firewire cables. The other common form of hard disk recording uses a dedicated recorder which contains analog-to-digital and digital-to-analog converters as well as one or two removable hard drives for data storage. Such recorders, packing 24 tracks in a few units of rack space, are actually single-purpose computers, which can in turn be connected to standard computers for editing.