This study presents a method for measuring sound absorption coefficients in reverberation chambers using total energy density to reduce the influence of room modes at low frequencies. The proposed approach calculates reverberation time from measured values of both sound pressure and particle velocity, rather than using sound pressure alone as in conventional methods. The particle velocity is derived from B-Format signals converted from recordings made with Ambisonics A-Format microphones. To evaluate the initial part of total energy density decay when calculating reverberation times, a method employing the damping density of the sound field, as proposed in previous research, is applied. The sound absorption coefficient is evaluated by comparing reverberation times measured in a reverberation chamber with and without the test sample, as in the conventional method. Sound absorption coefficient measurements were conducted using 50 mm glass wool with a 150-mm air layer as the test sample. The reverberation time determination method based on total energy density demonstrated improved spatial uniformity characteristics comparable to the conventional method based on squared sound pressure decay. Additionally, the method using total energy density showed a tendency to evaluate the sound absorption coefficient as higher compared to the method using squared sound pressure.
Goto et al. (Wed,) studied this question.