Acoustical Design and Measurement of a Circular Hall for Improved Spatial Factors at Each Seat

A round-shaped multi-purpose event hall (ORBIS Hall, Kobe, Japan) was designed based on the subjective-preference theory of sound fields [Y. Ando, Architectural Acoustics -Blending Sound Sources, Sound Fields, and Listeners-, AIP Press/Springer-Verlag, New York, 1998]. To avoid acoustical problems produced by round-shaped walls, and to maximize the total scale value of the subjective preference at each seat, acoustical features including several kinds of reflectors were carefully designed. The IACC calculated for the design phase, however, did not include all the installed features because these have complicated scattered reflection characteristics. After construction of the hall, therefore, the IACC measurements were conducted using two different music motifs. Results indicate that the values of the IACC are much improved due to these features. Also, the SPL-dip in the low frequency range in the area close to the stage is effectively improved by the inclusion of a perforated floor.