Optimizing sound diffusion in a concert hall using scale-model measurements and simulations

Abstract

To propose optimal guidelines for the diffusion design of concert halls, sound field variations in the presence or absence of reflectors (canopies and clouds) and diffusers were comprehensively examined in terms of stage and auditorium acoustics using 1:25 scale-model measurements and acoustic simulations. The sound field variations were investigated based on the just-noticeable differences. For stage acoustics, the stage support parameters STEarly and STLate were analyzed; for auditorium acoustics, the reverberation time (RT), early decay time (EDT), clarity (C80), and center time (TS) were analyzed. The canopies reduced the reverberations but increased STEarly and STLate. The clouds increased STEarly and reduced the deviation of the auditorium EDT and TS whilst increasing the initial EDT that had been reduced by the canopies. The diffusers decreased STEarly, STLate, RT, EDT, and TS regardless of the attachment position, and they increased the C80 of some auditoriums. However, diffuser attachments reduced the seat-to-seat deviations of acoustic parameters. Furthermore, attaching diffusers near to (as opposed to far from) the sound source represents the optimal design strategy for increasing the density of early reflections. This study is significant as an initial attempt to examine the effects of concert hall diffusion design in terms of both auditorium and stage acoustics, and it is significant in that it presents an appropriate method for evaluating the effects of a concert hall diffusion design that can be employed by architects and sound consultants. The findings of this study are expected to be suitable as basic data for the diffusion design of rectangular concert halls.