抄録
As a basic study on sound reflectivity of a panel array "clouds" in auditoria, the sound reflectivity of a rigid rectangular panel was calculated by the Fresnel-Kirchhoff's diffraction formula given by the Kirchhoff's boundary conditions, and compared with the measured values by the pulsed-tone method. Under the adequate restrictions, the approximate formula based on the Fraunhofer diffraction is more useful than that based on the Fresnel diffraction. The sound reflection from a panel of irregular shape was estimated by dividing it into rectangles and then summing their effects. A reflection-diffusion function is defined for an absorbing panel. For a reflecting uniform specularly panel, this function agrees with the reflection coeffcient as determined by the "Interference Method". The sound reflection from an array of square panels is calculated by summing the effect of each. Good agreement between theory and experiment has been found over a wide range of reflection angle and frequencies, except in the lower frequencies.
