optical sound

noun

, Movies.

1. sound recorded on and subsequently played back from an optical or photographic soundtrack, as opposed to a magnetic soundtrack.

optical sound

noun

1. sound recorded in the form of a photographic image on cinematograph films

Word History and Origins

Origin of optical sound¹

First recorded in 1930–35

Example Sentences

The conventional "optical" sound track on the edge of the film is replaced by a "sound-stripe" of magnetic material, as in a tape recorder.

From Time Magazine Archive