Release and re-buildup of listeners' models of auditory space.

When listeners hear sound presented repeatedly in a room with reflections, echo threshold rises. The current experiments tested how long this buildup in echo threshold would last when exposure to a different simulated space (designated as room B) intervened before returning to the original space (designated room A). Stimuli were trains of lead-lag click pairs (room A) and trains of clicks with no reflections (room B) in an ABA sequence. After buildup in room A, echo threshold for click pairs in room A decreased in direct relation to amount of intervening exposure to room B. After 11 click pairs of room B, the effect of exposure to room A was gone. A second buildup in echo threshold in room A was not differentially affected by prior exposure to room A or a different simulated room, room C. Listeners appear to form a model when exposed to sound in a particular space, which is lost quickly upon hearing sound in a different space. Storing previous models is inefficient because the processes of buildup and breakdown occur quickly to sound in a new space.