In situ measurements for evaluating the scattering surfaces in a concert hall

Abstract

Sound diffusion by a wall structure is one of the main concerns with respect to the sound quality of concert halls. There is a need to develop measurement and evaluation methods for determining the performance of scattering wall surfaces not only in a laboratory but also in actual halls. In this study, the acoustical measurements were conducted in a concert hall which has diffusers with ceramic cubic tiles on the side walls of the stage and the audience area. Binaural impulse responses were measured at all of the seats under two conditions, that is, with and without diffusers. The area which was affected by the diffusive wall was determined and quantified. The condition without diffusers was produced by covering them with the movable reflectors. From the binaural impulse responses, the temporal diffusion [H. Kuttruff, Room Acoustics, (Elsevier Science, London, 1991)], which is calculated from the autocorrelation of the impulse response, and other acoustical parameters were analyzed. From the relationship between the scattering coefficient and the acoustical parameters, sound scattering index for real halls, which represents the degree of the diffusion of a hall, was proposed.