Causes and Prevention of Systematic Deviations from True Values of Absorption Coefficients Measured in Reverberation Rooms

摘要

When absorption coefficients for materials in a localized arrangement are measured in reverberation rooms, values higher than the true absorption coefficient are obtained even in the case of optimal diffusion. Suggestions for separately measuring the absorption coefficient for randomly incident sound and the increase due to edge diffraction include: (1) two different arrangements of the absorptive material; (2) larger diffusers with much larger total area; (3) the inclination of certain room boundary surfaces and/or the use of a directional microphone; and (4) the calibration of the reverberation room with a material of known impedance and absorption.