1:10 축척모형을 활용한 오페라홀의 확산음장 평가

Abstract

The acoustic properties of a multi-purpose hall were measured in a 1:10 scale model to investigate the effect of scattered reflections on its opera mode. The elements of the scale model such as seats, audience, and absorption banners were made with material selected by absorption coefficient measurements in a 1:10 scale model reverberation chamber. Four orthogonal factors - listening level (LL), initial time delay gap between the direct sound and first reflection (Δt₁), subsequent reverberation time (T_(sub)), and magnitude of the interaural cross-correlation function (IACC) - were also investigated to evaluate the acoustical properties of the hall in its opera mode and to investigate the acoustical differences between stage and pit sources. The results showed that the difference in orthogonal factors in a hall between stage and pit sources was very significant. This difference was more pronounced in the stall area than in the balcony. The scattering coefficient measurements were conducted to determine the profile of diffusers to be applied to the scale model hall and provide data on the arrangement types, sizes and number of surface elements-hemisphere. Acoustical characteristics were also measured in stall area both with and without diffusers on the walls adjacent to the pit and on the side walls. The results showed that LL and T_(sub) decreased at most seats due to the absorption of the diffusers. The delay time between the direct sound and the reflection with maximum amplitude (defined as 'Δt₁') was delayed at the rear seat positions due to a change in the amplitude of the first reflected sound caused by the installed diffusers. It was also found that the installation of diffusers in several positions close to the walls adjacent to the pit decreased IACC. Amplitude and delay time of the first reflection were reduced by installing diffusers. Subjective evaluations showed that the diffusers on the side wall improve the auditory preference in the area around them. It was also found that significant factors for preference of scattered sound are T_(sub) and Δt₁.