Acoustics of Four Large Viennese Halls

At the Acoustical Society meeting in the fall of 1955, a paper was presented on the development of several types of room sound absorbers. These absorbers, which were tuned to a frequency of about 200 cps, had an absorption coefficient of more than 80% between 200 and 1500 cps. These absorbers have been used in the acoustical design and construction of four large Viennese halls. The largest hall, which is 100 yd long, 120 yd wide, and about 20 yd high, has a reverberation time of four seconds—exactly as planned. As a result of the nearly optimum shape of the hall, the intelligibility for random syllables spoken at the center of the hall is 96% at the remotest seats. This is equivalent to being adjacent to the speaker. Loudspeakers must be used, however, to overcome the noise produced by the audience. The second largest hall is 60 yd long, 30 yd wide, and 20 yd high. The side walls, which are made of glass arranged in a zigzag pattern, do not produce the slightest echo. The end walls are constructed of tune...