Dolby SR

Dolby Spectral Recording, commonly called Dolby SR, is a noise reduction process created by Dolby Laboratories. It is used in many aspects of analog recording but for the purposes of Sprocket School we will be talking exclusively about its use with 35mm and 70mm film prints. Dolby SR can be used to refer to the noise reduction process itself, or to the four channel sound format – left, center, right and surround. It is the most common optical sound format on films made after 1986.

Dolby logo that may appear in the end credits of some films recorded using Dolby SR.

Dolby SR vs. Dolby A

Dolby SR is difficult to distinguish from Dolby A by sight. Here are some tips on telling them apart:

• Some (but not all) films made after 1986 will have Dolby SR tracks, though A-type was still in use well into the 90s.
• Some (but not all) films with Dolby SR tracks will display the words "Dolby SR" with the Dolby logo in the end credits. Some (but not all) films with Dolby A tracks will display the word "Dolby" - or "Dolby Stereo" rather than "Dolby SR" - with the Dolby logo in the end credits. But be careful, just because you see one of these in the credits of the film does not guarantee that it is A Type or SR. Some films were released as both mono and stereo prints, or a film may have been re-mastered and released as SR but was originally mono. Seeing the logo in the credits is just another clue to be used with alongside other sources of information.
• Some (but not all) films with Dolby SR tracks will display the words "Dolby SR" on the edges of the film leader.
• A Dolby SR track played in Dolby A will usually sound fine, but will have more noise than you would expect from a soundtrack with Dolby Noise Reduction.

External Links

• Wikipedia: Dolby SR
• Wikipedia: [Dolby Pro Logic]