History
Movietone was perfected by Theodore Case and his assistant, Earl I. Sponable, in 1925 at the Case Research Lab in Auburn, New York, with their creation of what became the Movietone camera, built for the laboratory by the Wall machine shop in Syracuse, New York from a Bell & Howell camera.
Most single-system cameras were produced by Wall Camera Corporation, which much later produced the three-film Cinerama cameras. Wall initially converted some Bell & Howell Design 2709 cameras to single-system, but most were Wall designed and produced. Single-system cameras were also produced by Mitchell Camera Corporation during World War II for the U.S. Army Signal Corps, although these cameras were quite rare.
All single-system cameras share the same fault: the "sound translation point" is on the camera's main drive sprocket itself, and this contributes to significant 96 Hz flutter.
Double-system recorders, specifically those of the Davis Loop type, isolate the "sound translation point" from the drive sprocket(s), completely eliminating 96 Hz flutter, although a slight wow is still present at start-up. It is for this reason that the sound recordist announces "speed" a the beginning of a "take". The recordist observes the two compliance arms of the Davis Loop Drive and, indeed, which form the Davis Loop itself (sometimes referred to as a "Davis Tight Loop") and when the compliance arms become stationary the sound film is running true at 90 feet/minute (45 feet/minute for 17.5mm sound film and 36 feet/minute for 16mm sound film) and there is no wow or flutter. It is at this point that an assistant operator "slates" the "take". Of course, by this time the film camera(s) has (have) already come up to sound speed and these components will all remain in synchronism throughout the remainder of the "take".
Although single-system remained popular for news gathering, production sound quickly converted to the far superior double-system method.
Today's digital sound reproduction systems for motion pictures are generally dependent upon the presence of a Davis Loop Drive (example: Dolby Cat. 701 digital sound head; and one of the very few times on record that Dolby Labs has acknowledged another inventor's device).
Read more about this topic: Movietone Sound System
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