Sound Motion Picture Technology
By the early 1920s, the motion picture industry was going strong, but movies were still silent. Theaters hired musicisans from pianists to full orchestras accompany the film and make film going a more engaging experience. There had been many efforts to add sound to motion pictures, including those of Thomas Edison and Lee De Forest, but none had caught on. Part of the problem was that these earlier systems simply did not work very well. But American Telephone and Telegraph Company and RCA would succeed where others had failed.
AT&T's Bell Telephone Laboratories had already been working on many technologies that could be used with motion picture sound, including disc recorders, Audion electronic amplifiers, microphones, and loudspeakers. In 1922, Labs vice president for research Edwart Craft, realized that the company all the components needed for adding sound to motion pictures, except a means to synchronize the sound with the picture, In 1922 the Research Department of Western Electric Company (a part of AT&T that later became the famous AT&T Bell Laboratories) began working this, and they demonstrated the first one, called the Vitaphone, in 1925. This system used phonograph discs to store the sound. Since a standard reel of film played for 10.5-11 minutes, and existing 10 inch 78 rpm phonograph records played for 3-4 minutes at 78RPM, they had to devise a new standard: 12 inch records playing at 33 1/3 rpm. The turntable for playing back the discs was run off the same motor as the projector, thus assuring that if the cuing mark on the disc was lined up with the cuing frame on the film, the sound would be in syncronization. Warner Bros. studio released the first Vitaphone feature, Don Juan in 1926. It featured a prerecorded orchestral score and sound effects, but no dialog. The studio released the most famous early “talkie” The Jazz Singer, in 1927. Over a hundred theaters in the United States were equipped with the Vitaphone system by 1927.
But AT&T and others were already working on something quite different. The idea of putting the sound recording right on the film next to the image seemed like a better idea than having it on separate phonograph discs. Discs could skip or get out-of-step with the film. They also were almost impossible to edit once they were recorded. These limitations made it hard to make a movie.
Almost as soon as theaters had converted to the original Vitaphone, the improved sound-on-film system appeared. Between about 1929 and 1933, Western Electric, RCA, Fox-Movietone, and the Tri-Ergon, Tonfilm, and Klangfilm companies in Germany all had their own versions of optical sound-on-film. These competitors would fight it out for many years, but these sound-on-film systems quickly made sound-on-disc obsolete in the early 1930s. The same microphones, amplifiers, and loudspeakers could be used to make sound-on-film movies, so only the recorders themselves had to be changed. Western Electric, which had sold or leased sound-on-disc projectors to most of the theaters in the United States made it easy to switch to sound-on-film by offering an adapter that fit on existing projectors. The turntables and tonearms were simply removed.