Room tone

Room Tone (other terms are Presence or Atmosphere) is a location's "aural fingerprint" -- nonspecific sounds on the upper end (somewhere between 2000 and 8000 Hz).

Each room has a distinct presence of subtle sounds created by the movement of air particles in a particular volume. A microphone placed in two different empty rooms will produce different room tone for each.

Room tone is recorded during the sound recording of a film production. It is used to match the production sound track so that it may be intercut with the track and provide a continuous-sounding background. Use of room tone smooths out edit points and/or gives a feeling of "life" in an otherwise sound-deadened studio. The soundtrack "going dead" would be perceived by the audience not as silence, but as a failure of the sound system.