Acoustic scattering characteristics of Penrose-tiling-type diffusers

Periodic surfaces involve strong dependence of incidence angle and frequency on scattering directivity, which can be harmful to auditory tonal impressions in room acoustics, while non-periodic surfaces have potential in yielding uniform directivity and moderate frequency characteristics. This paper aims to develop a new type of aperiodic diffuser based on the Penrose tiling of the plane, and furthermore incorporating a fractal expansion for broadening the effective frequency range. In numerical calculation and scale model experiment, the effects of shape, height and arrangement of Penrose tiles on random- and normal-incidence scattering coefficients are examined. In addition, the uniformity of scattering directivity is evaluated in the calculation of directional diffusion coefficients.