Haas discovered in the experiment that if two different sound sources emit the same sound and reach the audience with the same intensity at the same time, the subjective feeling is that the sound comes from between two sound sources; if one of them is slightly delayed (About 5 to 35 milliseconds), it sounds that both sounds come from an undelayed sound source. The presence of the delayed sound source has no effect on the orientation of the direction, but only increases the loudness; if the delay is between 35 to 50 milliseconds, then The presence of a delayed sound source can be identified, but its direction is still in the direction of the undelayed sound source; only if the delay exceeds 50 milliseconds, the second sound source is heard as a clear echo. It can be seen that if two identical sounds occur within 50 milliseconds (1/210 seconds), they are generally indistinguishable, and only changes in timbre and loudness can be perceived if the second sound is delayed by 50 milliseconds. Appear, and there is enough loudness, we can distinguish them. This effect is applied to the indoor sound reinforcement system and can ensure the audience's visual and auditory consistency in the sound field of the distributed speaker system.
If the sound path difference between the reflected sound and the direct sound is more than 17 meters in the hall and the sound absorption effect of the room is not good, an echo will be produced, thus destroying the naturalness and intelligibility of the language. In addition, in larger halls, in order to ensure the uniformity of the sound field, there are often auxiliary speakers in the backcourt. 13 At this time, if the listeners in the back seat are seated, if the main speaker of the bench is closer to him than the backcourt assistant The speaker is 12 meters away from him (equivalent to the sound from the main speakers at the bench is 35 milliseconds later than the sound from the rear speaker), he will feel the sound from the back field, and at this time, in order to ensure the audience's visual and auditory Consistently, it is necessary to add a delay device to the rear auxiliary speaker. It should also be noted that we always assume that the two sound sources have the same volume. In fact, if the delay does not exceed 20 to 30 milliseconds, the volume of the leading channel can be attenuated (or the volume of the lagging channel can be increased), to change the position of the sound image.
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