The Orange Hall of the Kochi Prefectural Culture Center is a two‐floor‐type multipurpose auditorium of 10 620 m3 in size, provided with 1500 seats. This hall is designed so that the main and the second floors can be divided with a movable partition unit, which is housed in the ceiling when not in use, as required by the type of presentation. It can be used in three ways: as the full‐size hall, as a medium‐size hall using only the main‐floor auditorium with 1000 seats, and as a meeting room using only the second floor with about 350 seats. In order to furnish the hall with room acoustic conditions suitable for diversified use, suspended ceilings have been used in the auditorium as variable reverberation units. When these are lowered, the increase in the absorption power of the hall is about 150 m2 at 500 Hz, and the reverberation time is reduced to about 0.3 s. According to the results obtained, the reverberation time at 500 Hz in the empty hall is 1.7 s when the movable stage sound reflectors are used, 1.45 s when the suspended ceilings are lowered, and 1.15 s with the stage curtains lowered. Other characteristics have been realized as expected in the design.

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