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概要

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An auditorium, having about 1000 seats, was constructed in the Kure Civic Center. A plane shape of this auditorium was designed originally as circular audience area. As is well-known, circular shape auditorium would have several acoustic defects, especially acoustic focusing or long-delayed echo. These phenomena were confirmed by the two-dimensional ray tracing analysis. To remove these defects, it was decided to adopt diffuse and absorbing walls. For the detailed design, three-dimensional model was made, and by using the optical method the paths of reflected wave from the diffuse wall and ceiling were investigated. From these investigations, the shape of the diffuse wall and the position of absorbing wall were determined so as to avoid the intense primary or secondary reflected wave which arrive at the audience area aelayed more than 50 milliseconds after the arrival of the direct wave. Acoustic investigation after the completion of this auditorium has shown that any acoustic defect due to the circular shape was not observed. Reverberation time of empty auditorium is 1.6 seconds at 500 cps., and from calculation it would be expected to become 1.1 seconds for the full audience condition. This seems to be a optimum value for such auditorium used for various purposes.
社団法人日本建築学会の論文
1964-05-30