Phonofilm

Phonofilm is an optical sound-on-film system developed by inventors Lee de Forest and Theodore Case in the 1920s.

In 1919 and 1920, Lee De Forest, inventor of the audion tube, filed his first patents on a sound-on-film process, DeForest Phonofilm, which recorded sound directly onto film as parallel lines. These parallel lines photographically recorded electrical waveforms from a microphone, which were translated back into sound waves when the movie was projected. Some sources say that DeForest improved on the work of Finnish inventor Eric Tigerstedt — who was granted German patent 309.536 on 28 July 1914 for his sound-on-film work — and on the Tri-Ergon process, patented in 1919 by German inventors Josef Engl, Hans Vogt, and Joseph Massole.

The Phonofilm system, which recorded synchronized sound directly onto film, was used to record vaudeville acts, musical numbers, political speeches, and opera singers. The quality of Phonofilm was poor at first, improved somewhat in later years, but was never able to match the fidelity of sound-on-disc systems such as Vitaphone, or later sound-on-film systems such as RCA Photophone or Fox Movietone.

The films of DeForest were short films made primarily as demonstrations to try to interest major studios in Phonofilm. These films are particularly valuable to entertainment historians, as they include recordings of a wide variety of both well-known and less famous American vaudeville and British music hall acts which would otherwise have been forgotten. Some of the films, such as Flying Jenny Airplane, Barking Dog, and a film of DeForest himself explaining the Phonofilm system (all 1922) were experimental films to test the system.

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