Dolby Tech Page

Many people contribute to these guidelines. Particular thanks are due to David Schwind of Charles Salter Associates for much of the acoustic advice. Elizabeth Cohen of Cohen Acoustics, John Eargle of JBL and Tomlinson Holman of USC and Lucasfilm, provide significant contributions to this ongoing project. From within Dolby Laboratories there are numerous witting and un-witting contributors: in particular Tom Bruchs, Sam Chavez, Louis Fielder, John Iles, Lonny Jennings, Scott Robinson, Charles Seagrave and David Watts.

Some manufacturers' equipment is specifically cited in this material. Such citations are definitively non-exclusive -- manufacturers are welcome to contact Dolby Laboratories with information about any equivalent or superior performance equipment that they believe should be included in future editions of these guidelines. Omission of specific equipment does not imply lack of fitness.

Ioan Allen
September 20th 1993

@Dolby Laboratories Inc. 1992/1994
S95/9557/10447

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Modern film sound-tracks are proving increasingly demanding to exhibitors; not only is the theatre owner being asked to buy new frontend decoding equipment for a variety of sound-track formats, but these new formats are placing increasing demands on many aspects of theatre sound.

Dolby Laboratories has published a series of documents over the years, discussing the requirements of each progressively improved soundtrack format the company has introduced. This booklet provides guidelines for theatres trying to take full advantage of the most common existing sound-track formats at the time of writing, and anticipates what increasing demands the digital sound-track on Dolby SR•D prints may present.

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New Sound-track Formats

We should begin by re-iterating what seems fairly obvious to the engineers involved in film sound-track technology, what is frequently missed by some people involved in exhibition, and is certainly misunderstood by much of the movie-going public -- the sound-track format, mono, Dolby Stereo, Dolby Stereo SR, and now the digital sound-track of Dolby SR•D, does not itself define how loud or quiet a sound-track will be, or how extended the frequency response. The film-maker determines the artistic extents of the sound-track, not the format designer. The film-maker decides during the post-production process how loud the loudest bits of his films should be, how quiet the quietest -- how extended the frequency range should be, how wide the stereo, and how loud the surround effects. The role of the inventor, scientist and engineer involved in the technology of film sound is to make it possible for the full artistic range of the director to be carried on the film sound-track. And the role of the film exhibitor is to ensure that this full sound-track capability can be reproduced in the theatre.

The two Dolby Stereo formats most challenging for theatre playback are Dolby SR and the digital sound-track of Dolby SR•D release prints. The analog SR format is in some respects less demanding of theatre criteria, but in some areas, especially the A-chain, requires as careful attention as the new digital sound-tracks. These guidelines discuss these issues, and explain the minimum acceptable playback parameters for both of these new high-fidelity sound-track formats.

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