The effects of cylindrical diffusers on sound diffusion in a rectangular concert hall

Abstract

Acoustical measurements in a 1:20 scale model were conducted to investigate the influence of a 1/4-cylinder diffuser on sound diffusion in a rectangular concert hall. Diffusion was evaluated regarding temporal and directional distribution of acoustical energy at individual seats as well as energy distribution over all seats. With volume of 19,000 m3 and seating area of 1,200 m2, the size and shape of the hall were determined based on three classical rectangular concert halls. Overall, diffusers around the stage were more effective for the source at the center, front of the stage than the source at the side, rear of the stage. The hall average values of late interaural cross correlation (IACCL3) were reduced by using transversal diffusers on ceiling or longitudinal diffusers on the side walls. Although the influences on the hall average values of echo criteria (EC) and temporal diffusion (TD) were relatively small, diffusers on the rear stage wall were effective in reducing EC values for the seats near the side walls. Strength factor (G) at the seats under the balcony was significantly increased by placing diffusers on the ceiling. On-going research is conducted to evaluate the effects of diffusers in the audience section. [Work supported by the National Science Council of Taiwan.]