| Keywords |
Sound absorption coefficient; Impedance tube method; Reverberation room method; Noise barrier; Acoustic performance prediction |
| Abstract |
In this study, the applicability of normal-incidence sound absorption coefficients measured using the impedance tube method for predicting random-incidence absorption characteristics in a reverberation room was investigated through room acoustic simulation. Four types of porous sound-absorbing materials were tested, and their absorption coefficients were measured using both the impedance tube method and the reverberation room method in accordance with relevant standards. A numerical model of the reverberation room was developed using the ODEON software, and the model was calibrated by matching the simulated reverberation time with the measured reverberation time of the empty room. The calibrated model was then used to simulate the reverberation room conditions with test specimens installed. The normal-incidence absorption coefficients obtained from the impedance tube measurements were converted to octave bands and applied as input parameters for the simulation. The predicted reverberation time and corresponding absorption coefficients were compared with the measured results from the reverberation room. The results showed that discrepancies between measured and simulated reverberation time were observed, particularly in the low-frequency range. However, after calibration of boundary conditions, the simulated results showed good agreement with the measured reverberation room data across most frequency bands. In contrast, the use of averaged absorption properties resulted in increased deviations, especially at higher frequencies. These findings indicate that while direct application of impedance tube data has limitations due to differences in incidence conditions, calibrated room acoustic simulation can effectively improve the prediction accuracy. The study demonstrates the potential applicability of impedance tube measurements for predicting reverberation room absorption performance when appropriate model calibration is applied. |