- An acoustic phenomena in which a listener correctly identifies the direction of a sound source that is heard by both ears, but which arrives at each at slightly different times. If the second arriving sound, that heard by the ear farther to the source, is within about 10 to 35 milliseconds of the first arriving sound, it is not taken into account for locating the sound source. If the sounds arrive within less than 10 milliseconds of each other, the source seems to move towards the location of the first arriving sound. When said sounds arrive beyond 35 milliseconds of each other, two distinct sounds are perceived. This effect is taken into account in the reproduction of stereophonic sound. Also called precedence effect.