This film takes the viewer behind the scenes at Bell Laboratories while the new motion picture sound systems were being invented and tested. The foray into motion picture sound was a natural move for the Bell System -- already specializing in communications - but it also had a high profile at the time. This film, made using the Vitaphone sound developed at the Labs, shows testing of huge theater speakers, a visual light method of microphotography, the cutting of a wax disc for a Vitaphone system, and fatigue tests for equipment and film.
The most interesting part of the film is the display of the then-experimental soundtrack method of film sound: a thin tape was applied to the side of filmstrip - the sound track - and it vibrated with voices from a microphone. As the film states, "the voice photographs itself". Then Francis F. Lucas, a leader in microscopic photography, examines the film and soundtrack under UV light.
Due to a support agreement with Warner Brothers, soon the Bell System's methods of sound recording and playback were prevalent in Warner theaters nationwide - over 1,000 by the end of 1928.
Footage courtesy of AT&T Archives and History Center, Warren, NJ