精密音流計による拡散壁面の音響散乱効果の研究

抄録

At the acoustical designing of the auditoriums, etc. , we have several sorts of ways to diffuse the sound fields in the rooms. In these researches, model tests were carried outs in an anechoic room with the Precision Sound-Energy Flux Meter to know the scattering effect of sound energy by the diffuser which is generally used. The anechoic room has a dimension of 3. 2×2. 9×3. 5m^3 and in it the sample of 90×90cm^2 was placed for the measurement. We used three samples; one was a flat plane, the next a polycylindrical diffuser which consisted of 3 elements of semi-cylinders of 30cm at the base and the 7. 5cm in height, and the third a triangular diffuser which consisted of 3 elements of triangles of the same size. The sound power flow density was measured along the surface of the sample with the Sound-Energy Flux Meter. The measuring frequencies were 800 c/s, 1000 c/s, 2000 c/s and 4000 c/s; the incident angles of the sound against the normal of the surface of the sample were 0°, 30° and 60°. The surface of every sample was made of hard board to be reflexible. The results are expressed as vectors whose length represent the sound power flow density, and also as angular distribution of the vectors. The scattering effect is showed quantitatively by the ratio peak/σ, where peak shows the peak value of the vector, and σ is the standard deviation of angle distribution of vectors. It is concluded from the results that the polycyrindrical diffuser has more scattering effect than the triangular one when incident angle θ is small. When θ becomes larger, this effects appears in higher frequencies.