Buzz Track

The term buzz track usually means general ambient sound, i.e. the background sound of a scene. It is sometimes used more specifically to mean room tone.

Buzz tracks are typically recorded on location before or after the main action has been recorded. It is used as a sound bed to accompany any new sound that is added during post-production

Note: Buzz track is also a term used to describe a special type of film used to align projection equipment.