| Summary: | 碩士 === 國立屏東科技大學 === 木材科學與設計系所 === 105 === According to ISO 17497-2 method of measuring directivity diffusion coefficient were described. Techniques for this research were including the Semi-anechoic chamber (room volume were 75 m³) and two-dimensional Semi-automatic measurement system; therefor discovered diffusion performance among the different diffusion materials, diffuser sequences and the characteristics with the scattering coefficients. For recorded the reflected sound energy into directivity and normalized diffusion coefficients to calculated random incident diffusion coefficient, material and the reference plane must place on different angles of sound source positions, there were total 37 receiving points distances each 5 degree on near and far field. Diffusers were made by MDF (Medium-density fiberboard) and Douglas fir; the scale of diffuser was length of 67 cm * 67 cm and the reference plane made reference flat surface with diffusers. Result shown 0.6 m was the best receiving distance on near field; 0.9 m was the maximum boundary of far field measurement range. Compared to the near field diffusion performance were inefficiency, but there still some peaks certain degrees. The characteristics among material changes, these diffusers were no significant diffusion performance; experiment condition of sound source positions, diffusion performance were significant on ±30°、±60° in mid frequency bands; MDF diffuser shown peaks on low, high frequency bands. Compared all diffusion performance, MLS diffuser was better than that QRD sequence on certain frequency bands, but the average diffusion coefficients were resembled.
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