Definitions for "Haas Effect"
(aka precedence effect), tells us that humans localise a sound source based upon the first arriving sound, if the subsequent arrivals are within 25-35 milliseconds they are ignored. This is true even when they are up to 10dB louder than the first.
Simply stated, a factor in human hearing where delay has a much bigger effect on human perception of direction than level does.
See Precedence effect.
Keywords:  rack, half