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The optical audio track

At the beginning movies where just a visual experience. The only sound(track) was the music (a band) played to give the audience a certain atmosphere while watching a movie. Then in 1909 Eugene Lauste, a Belgian who lived in England, developed the first 'photographic sound track'¹, a technique used even today to capture audio beside the film cell. The newsreels in the 20's already used this technique.
One of the first experiments to make music more stereophonic was done by Alan Blumlein at EMI Records in 1923 because of the lack of other mediums.
The first popular feature movie with sound used a sort of LP to take advantage of the 'soundtrack'. It was called 'The Jazz Singer'. The problem with that one was: the LP had the same playing time as the movie ribbon, so the projectionist had to synchronize both. With the photographic sound track it was much easier, because it was attached to the ribbon and need not to be synchronized. That is why photographic sound catch on until today.

In 1938, Walt Disney introduced a new sound-system called 'Fantasound', this system was initiated along with the movie 'Fantasia'. But it was to complex to succeed. Fantasound used a second movie ribbon (the follower) with three photographic sound tracks and a control track on it². The follower had to be synchronized with the feature movie, too. Today you can buy Fantasia in Dolby Stereo.
But Fantasound was only one of many other attempts to make the sound match the broader picture, that has developed over the years. For example 'Cinerama', a system with three projectors for the picture and a fourth one for a follower with seven audio tracks, which referring to the immense expense had no success either.

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The magnetic audio track

While the photographic sound track established itself, another method approached on the market. The audio recording on 'magnetic tapes'. An oxide track was attached to the 35mm celluloid and was then the sound was written down on it just like on a cassette tape. With this new method four audio tracks where possible. One channel for left, front and center and one for the effects (just the effects, in contrast to systems today). Each channel got a speaker and the effects channel got several speakers around the back of the spectators. The first feature movie with this so called 'CinemaScope'³ system was 'The Rope' by Alfred Hitchcock in 1952.
Some other systems appeared and disappeared on the market, too. For example, 'Todd AO', with a 70mm movie ribbon and six magnetic audio tracks, or 'Sensurround' a system that basically used impressive subwoofers⁴, which sometimes let fall the plaster from the ceiling.
But magnetic tracks on celluloid had two major disadvantages: First, they were very expensive. A 70mm movie with magnetic tracks cost about 20 times the price of a 35mm movie with an photographic sound track. Second, the oxide crumbled away after several times of playing.

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Dolby^® Stereo

In 1974 the Dolby Laboratories introduced Dolby Stereo to the media. But it was not fully operational until 1976, when 'A Star Is Born' with Barbara Streisand⁵ and Kris Kristofferson⁶ appeared in the cinemas. It was the first movie with the so called Dolby Stereo (optical)⁷ system.

Dolby Stereo consisted of two seperate techniques:

1. 'Dolby-A noise reduction'
2. 'Dolby-MP⁸-Matrix encoder'

Dolby-A was developed in the late 60's by the sound engineer Ray Dolby. Dolby originally created it for the use with tape recordings⁹, but it worked well with movies, too. The Dolby-MP-Matrix encoder was constructed by Ioan Allen. It enabled the Dolby engieers to put four audio channels into two photographic sound tracks, which means it was now possible to produce a cheap multi-channel soundtrack on a 35mm film¹⁰.A medium the most cinemas were able to play.
Dolby Stereo's triumphant advance began in 1977 with the movies 'Star Wars' and 'Close Encounter Of The 3rd Kind', both movies who took full advantage of this new system.

1986, the Dolby labs extended Dolby Stereo with the SR¹¹-technique which enhanced the recording quality, so it nearly reached the quality of 70mm movies. One of the first films which used Dolby SR was the action movie 'Robocop' by Paul Verhoeven in 1988.

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Digital sound systems

In 1991 Kodak¹² changed the scenery of cinema sound with the movie 'Dick Tracy' and their new digital system 'CDS'¹³, which didn't succeed because, for example, it replaced the analog audio. But it startled Dolby and in a hurry they announced their own digital sound system, then called 'SR.D'. However it took one year before it had finally premiere with 'Batman Returns' in 1992. Warned by the CDS desaster, Dolby didn't replace the analog track, but put the bits and bytes between the perforation. The advantage of this technique is that every cinema in the world could play one and the same copy of the film, because it contains everything on one movie ribbon. A simple equipped cinema could play it in mono, the better in stereo and the up-to-date ones with digital sound. This combination of the SR optical audio and the digital recording led to the name SR.D, which was later replaced with 'DSD'¹⁴. Later they let the word Stereo fall flat, so today it is simply called 'Dolby Digital'

Until today several new digital sound systems appeared on the market.On the one hand there is 'DTS'¹⁵, which had its breakthrough with Steven Spielbergs megaseller 'Jurassic Park' in 1993. On the other hand we have 'SDDS'¹⁶
Last year (1999) a new Dolby release showed up: 'Dolby Digital EX'
Dolby Digital EX adds a new channel to the six¹⁷existing channels: the rear center. First it could be seen in George Lucas' sequel 'Star Wars: Episode I - The Phantom Menace'. Some other movies with this new standard are 'Austin Powers 2: The Spy Who Shagged ME' and 'The Haunting', for example.

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The enhancement in sound quality: THX

'THX'¹⁸is not a sound system, but a system to improve the audiovisual quality of cinemas. It works with every system that is used today, simply because it is just some kind of quality seal. THX is a rulebook for the fidelity of reproduction of a movie theater. A theater with the THX seal is inspected to keep the standards of high quality movie reproduction in sound and picture every 12 months.

Here a short extract of THX's history:

• In 1982 the first THX mixing room opens at Lucasfilm.
• 1983 THX Division of Lucasfilm, Ltd is created;
  two THX theatres open in time for the release of 'RETURN OF THE JEDI' in the same year
• 1990 Home THX Program is introduced
• 1993 THX Laser Disc Program is created; quality control services are offered to studios for films during video disc production
• 1996 Laser Disc Program expands to include videotape and DVD. Name is changed to THX Digital Mastering Program
• 1997 More than 1,600 certified movie theatres and mixing rooms are created around the world
• 1998 THX announces certification standard for DVD players.

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¹ Aside the film cell of a movie ribbon there is a certain track that contains transparent and non-transparent parts in the shape of sound waves. When you shine with a light through it, you are able to transform the light which passes through into sound waves.
² So the whole movie had eight music tracks!
³ By the way CinemaScope is also a system that includes the picture: It compresses the picture horizontally at the recording and decompresses it at the projection so you got a broader picture. But I will explain this in another guide entry about the several picture formats of a movie.
⁴ Big loudspeakers used only for deep frequencies below 100Hz or deeper.
⁵ She is a famous singer and played in several films e.g. 'What's up Doc?'
⁶ He played the trucker in 'Convoy', for example. But the younger of you might recognize him as the big boss of the 'Outfit'-syndicate in Mel Gibson's 'Payback'.
⁷ Because you could use it on magnetic tapes , too.
⁸ Motion picture
⁹ If you got a cassette player it might have Dolby-B,-C,-S or even HX Pro NRNoise Reduction
¹⁰ A 35mm copy with optical audio cost half the price of a 35mm copy with a magnetic audio track
¹¹ Spectral Recording
¹² Kodak doesn't offer any deeper information on this project anymore; you just find it mentioned in a brief history
¹³ Cinema Digital Sound
¹⁴ Dolby Stereo Digital
¹⁵ Digital Theater Systems
¹⁶ Sony Dynamic Digital Sound
¹⁷ front left, front center, front right, rear left, rear right and the LFE (Low Frequency Effect)
¹⁸ Tomlinson Holman's eXperiments