Some issues in measurement of the random-incidence scattering coefficients in a reverberation room

In recent years, the ISO working group has standardized the measurement methods for a scattering coefficient for surfaces in rooms, ISO 17497-1. The importance of the application of the scattering coefficient in room acoustics, particularly in a computer model to obtain reliable prediction results, has already been reported in international round robin tests. There is a need for guidelines and a reliable database of surface materials for the application of the standard method. In this study, the effect of some measurement parameters on the measurement of randomincidence scattering coefficient in a reverberation room based on ISO 17497-1 was investigated. A 1:5 scale model of the reverberation room, which has a volume of 2.4 m³, was employed to measure the random-incidence scattering coefficient of periodic battens. In the present work, three parameters, the turntable diameter (0.64 m and 0.84 m), the air gap below the turntable (50 mm and 222 mm) and the absorption coefficient of the test sample (0.09 and 0.31) were considered. The influence of each parameter over the scattering coefficient of the periodic battens was measured and analysed. A lower scattering coefficient of the periodic battens was obtained when a turntable diameter of 0.64 m was applied. A lower scattering coefficient of the periodic battens at the corresponding real-scale frequency bands from 630 Hz to 2.5 kHz was obtained when an air gap of 50 mm was applied. The absorption coefficient of the test sample influenced the measured scattering coefficient at mid and high frequency bands.