"If it can be written, or thought, it can be filmed..." STANLEY KUBRIC
From Encyclopedia PRO
Sound which is indigenous to the action but not precisely synchronized with the action.
In a closeup in which the surroundings are not visible, a sound that seeps into the shot sometimes impresses us as mysterious, simply because we cannot see its source. It produces the tension arising from curiosity and expectation. Sometimes the audience does not know what the sound is they hear, but the character in the film can hear it, turn his face toward the sound, and see its source before the audience does. This handling of picture and sound provides rich opportunities for effects of tension and surprise.
Asynchronous Sound (that is, when there is discrepancy between the things heard and the things seen in the film) can acquire consid erable importance. If the sound or voice is not tied up with a picture of its source, it may grow beyond the dimensions of the latter. Then it is no longer the voice or sound of some chance thing, but appears as a pronouncement of universal validity. The surest means by which a director can convey the pathos or symbolical significance of sound or voice is precisely to use it asynchronously.