Question about physic of sound

Posted on 2013-11-27 16:48:00 in Engineering by CONG

Recall the apparent size of a concert hall, acoustically speaking, depends on the time between the direct sound wave (from the performers to your ears) and the ?rst re?ected sound wave (i.e., with one bounce o? of a side wall or the ceiling). Research by Hidaka and Beranek concluded that this “initial-time-delay gap” is about 20 ms or less for the best-sounding opera houses, and it was not much smaller than this for any large opera house (the smallest delay they measured was about 15 ms). In large concert halls, where the ?rst wall and ceiling re?ections would come too late, the intimate character can be preserved by adding a “sound canopy,” usually a set of panels acting as a lowered ceiling, designed to provide an earlier ?rst re?ection to the audience. (For a good example, see the photograph of the Munich Philharmonie in the lecture slides.) Suppose you are an acoustical engineer, called in to a large concert hall to address complaints that the sound for audience members in the front center (right in front of the orchestra/stage) is not good because it lacks an intimate character. You recommend installing a sound canopy over the orchestra. Estimate the height above the audience/orchestra that you should recommend for the sound canopy. Give your answer in both m and ft, and explain.

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