Precedence effect

The precedence effect or law of the first wavefront is a binaural psychoacoustical effect concerning sound reflection and the perception of echoes. When two versions of the same sound presented are separated by a sufficiently short time delay (below the listener's echo threshold), listeners perceive a single auditory event; its perceived spatial location is dominated by the location of the first-arriving sound (the first wave front). The lagging sound does also affect the perceived location; however, its effect is mostly suppressed by the first-arriving sound.

The Haas effect was described in 1949 by Helmut Haas in his Ph.D. thesis. The term "Haas effect" is often loosely taken to include the precedence effect which underlies it. Provided by Wikipedia