Temporal masking

A loud sound can mask a soft sound that does not occur at precisely the same moment. *Post or forward masking* occurs when a loud sound masks a lower one right after it. Loud sounds can mask ones before it as well, since the brain perceives the louder sound more quickly. This is called *premasking or backward masking*, and is not too drastic as it usually occurs mostly within 10ms or 1 peforation of 35mm film at 24fps. Sound editors use backward masking to cover up discontinuities at edits.