Reverberation Measurements of Sound Absorption Coefficients

Abstract

A comparison is made of the results of the measurement of the absorption coefficients of twenty-five commercial materials by the organ pipe and ear method with the results obtained by measuring the rates of decay by electrical means. A consistent variation in these results is shown, which can be explained by assuming a slight departure from linearity in the time versus logarithmic intensity relation.

Air Absorption Error in Room Acoustical Modeling

“…It was Sabine [1] who in 1929 first noticed a variation in the reverberation time of an empty reverberation room in his laboratory, caused by different climate conditions. In 1931 Knudsen [2] proved that this effect was not caused by a change of absorption properties of the surface material, but by the change of absorption properties of the air, when temperature and humidity changes.…”

“…In 1931 Knudsen [2] proved that this effect was not caused by a change of absorption properties of the surface material, but by the change of absorption properties of the air, when temperature and humidity changes. Extensive research by many scientist lead to the standardized calculation model in ISO 9613-1 [3] and ANSI S1.26 [4] for pure tone air absorption based on sound decay measurements in reverberation rooms [1,2,5,6] and impedance tubes [7,8,9,10,11,12], with varying frequency range, gas mixtures and climate conditions. The final calculation model is presented in literature [13,14,15].…”