Investigation of sound field diffuseness in an irregularly-shaped room based on FMBEM incidence directivity analysis

Several methods to evaluate sound field diffuseness have been proposed in terms of the isotropy of traveling sound waves. In a previous paper, we investigated the characteristics of two kinds of diffusion indices in a rectangular room, based on the incidence directivity analysis employing the FMBEM. The present study applies the incidence directivity analysis to an irregularly-shaped reverberation room for measurement of sound absorption, and investigates the effects of room shapes and absorbing surfaces on the diffusion indices. The numerical results show that the indices tend to be higher in an irregularly-shaped room than in a rectangular room, and those decline remarkably with increasing the absorption coefficient of the walls. Moreover, the tendencies are more clearly seen in the diffusion indices for the 1/3-octave bands than for single frequencies.