An in-situ diffusivity measurement method for diffuser design in concert halls.

Abstract

This study investigates an in-situ measurement method to evaluate the diffuseness of a sound field using scale model concert halls. The diffusers were applied to scale model concert halls in which the impulse responses at both the audience and stage area were observed. Both reflection number (RN) and reflection energy (RE) were used as in-situ diffusivity indices: RN is defined by the number of reflection rays of which critical amplitude level is within −30 dB after the direct sound, and RE defined by the integrated energy at the normalized impulse responses. Through the scale model measurements, it was observed that half of the side walls near the stage were effective for diffuseness of sounds both in auditorium and on stage. It was also found that the balancing of in-situ diffusivity is useful for diffuseness perception, which is subject to the level of the direct sounds.