Definition for Sound Track
From Biology Forums Dictionary
That portion of the sound film medium to which are recorded the dialogue, music, narration and sound effects. The sound head and film gate on a film projector are physically separated from one another. This gap is covered during the recording of a sound-film by keeping the soundtrack recording a few frames head of the photographic image. The sound passes over the projector head at the same time the photographic image passes before the projector's light aperture/lens (the film gate).
