If sounds arrive from several sources, the ears and brain will identify only the nearest. In other words, if our ears receive similar sounds coming from various sources, the brain will latch onto the sound that arrives first. If the time difference is up to 50 milliseconds, the early arrival sound can dominate the later arrival sound, even if the later arrival is as much as 10 dB louder. The discovery of this effect is attributed to Halmut Haas in 1949.
The Haas effect is a psychoacoustic effect, also known as the Precedence Effect or law of the first wave front. A listener hears two identical sounds (i.e. identical soundwaves of the same intensity) from two sources: A and B. The sound created at source A, which is closer to the listener than source B, arrives first.