Vitaphone (film sound process)
Vitaphone was a sound film system used for feature films and nearly 1,000 short subjects made by Warner Bros. and its sister studio First National from 1926 to 1931. Vitaphone is the last major analogue sound-on-disc system and the only one that was widely used and commercially successful.
The soundtrack is not printed on the film but issued separately on phonograph records. The discs, recorded at 33+1⁄3 rpm (a speed first used for this system) and typically 16 inches (41 cm) in diameter, are played on a turntable physically coupled to the projector motor while the film is projected.
Its frequency response is 4300 Hz. Many early talkies, such as The Jazz Singer (1927), used the Vitaphone system. The name "Vitaphone" derived from the Latin and Greek words, respectively, for "living" and "sound".
Warner Bros. introduced Vitaphone on August 5, 1926, with the premiere of their silent feature Don Juan, which had been retrofitted with a symphonic musical score and sound effects. There was no spoken dialog. Don Juan was able to draw huge sums of money at the box office but was not able to recoup the expenses Warner Bros. put into the film's production.
From the perspective of the cast and crew on the sound stage, there was little difference between filming with Vitaphone and a sound-on-film system. In the early years of sound, the noisy cameras and their operators were enclosed in soundproofed booths with small windows made of thick glass.
Cables suspended the microphones in fixed positions just above camera range, and sometimes they were hidden behind objects in the scene.
The recording machines were usually located in a separate building to completely isolate them from sound stage floor vibrations and other undesirable influences. The audio signal was sent from an on-stage monitoring and control booth to the recording room over a heavy shielded cable. Synchronization was maintained by driving all the cameras and recorders with synchronous electric motors powered from a common source.
When music and sound effects were being recorded to accompany existing film footage, the film was projected so that the conductor could synchronize the music with the visual cues and it was the projector, rather than a camera, that was electrically interlocked with the recording machine.
Except for the unusual disc size and speed, the physical record-making process was the same one employed by contemporary record companies to make smaller discs for home use. The recording lathe cut an audio-signal-modulated spiral groove into the polished surface of a thick round slab of wax-like material rotating on a turntable.
The wax was much too soft to be played in the usual way, but a specially supported and guided pickup could be used to play it back immediately in order to detect any sound problems that might have gone unnoticed during the filming.
If problems were found, the scene could then be re-shot while everything was still in place, minimizing additional expense.
Even the lightest playback caused some damage to the wax master, so it was customary to employ two recorders and simultaneously record two waxes, one to play and the other to be sent for processing if that "take" of the scene was approved.
At the processing plant, the surface of the wax was rendered electrically conductive and electroplated to produce a metal mould or "stamper" with a ridge instead of a groove, and this was used to press hard shellac discs from molten "biscuits" of the raw material.
