Non-uniform sound intensity distributions when measuring absorption coefficients in reverberation chambers using a phased beam tracing

Abstract

Measured absorption coefficients in reverberation chambers often differ from theoretical random incidence absorption coefficients, because ideal assumptions for the theoretical random incidence absorption coefficient are not fulfilled during measurements in actual reverberation chambers. Therefore sound intensity distributions on absorber under measurement conditions have been simulated using a phased beam tracing, and used as correction functions for reducing discrepancies between the measured and theoretical absorption coefficients. Two reverberation rooms were investigated by assuming that a test specimen was attached to a vertical surface and the floor. The frequency-dependent sound intensity distributions on absorbers were found to be affected by the reverberation chamber geometry and dimensions, the absorption capability of the specimen, and the placement of the specimen. High frequency intensity distributions above 1 kHz were similar for all studied cases, but some variations in low frequency intensity distributions were observed. If the non-uniform intensity distribution and a finite size effect are taken into account for correcting the theoretical absorption coefficients, a good agreement is found between corrected and measured statistical absorption coefficients. The non-uniform sound intensity can account for the discrepancy at high frequencies.

The forced sound transmission of finite single leaf walls using a variational technique

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The equivalent incidence angle for porous absorbers backed by a hard surface

“…14,16,17 Therefore, the increased absorption coefficients may lead to larger incidence angles, particularly for high absorption coefficients above 0.8 as can be seen in Figs. 5 and 6.…”

A Comparison of Different Techniques for Simulating and Measuring Acoustic Parameters in a Place of Worship: Sant Jaume Basílica in Valencia, Spain

“…Although we have not used these tools, their use should be considered by researchers. However,itisw orth noting that their use presents some problems [47].…”