Quantitative evaluation of three-dimensional shape of auditorium using elliptic Fourier descriptors

Roughness of ceilings and walls in auditorium is one of the most important points of acoustic design, because the roughness of wall surface is highly related to prevention of acoustic glare and quality of sound. The roughness is now often evaluated by the surface diffusivity index, SDI, which is visual inspection by using photographs or drawings, which is not objective evaluation, proposed by Haan and Fricke[1,2,3]. In this paper, we propose an objective evaluation method of three-dimensional roughness of wall surface. This method is realized by elliptic Fourier descriptors and extracts cycle length and amplitude of complex surface shapes, and offers characteristics of the three-dimensional shapes as spatial frequency characteristics.