Sound Recording And Reproduction (1941)

Describes how sound is converted into light rays to produce sound motion pictures and how the light rays are converted back into sound waves. Shows sound recording by both variable area and variable density. Features footage of James A. Brill, the narrator of many ERPI and early Encyclopedia Britannica films.
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[@omega6872]

Better explained than in my college

[@internationalremixes6440]

i would love to watch more classical videos like this!!

[@marklimbrick]

Does not show how the light shutter is used to produce the variable area soundtrack? Maybe a patent issue? The shutter ribbons must increase and reduce the width of the line on the film, which has constant illumination. Strange not to explain this. The film also shows that the shutter increases the width of the line to correspond with the sound level, which would make the frequency response depend on the volume of sound. There will always be some halation (light spread/spill and reflection from base material, not 'lens flare') in the film emulsion, but this illustration is a bit weird. You couldn't have loud, high frequencies? Something got mixed up in the conversation between the technical people and the educational film production studio.

[@elgeneralxx]

Creepy