Measurement uncertainty of sound absorption coefficient measured in a 1:8 scale reverberation room

The measurements of sound absorption coefficient in a scaled reverberation room are mainly used for the purpose of choosing the materials for acoustic scale models. Another application of scale model measurements of sound absorption coefficient is testing multiple variants and modifications of special acoustic elements, once their scale equivalents are found. Regardless of the purpose of the sound absorption measurement, the measurement accuracy should be known, and therefore it is necessary to determine the measurement uncertainty budget. The measurement procedure is based on the one described in the ISO 354 standard, which means that the measurement of sound absorption coefficient is an indirect type of measurement, and the final measurement uncertainty depends on the uncertainties of all the measured input values. The paper describes an approach to determining measurement uncertainty of sound absorption coefficient measured in a 1:8 reverberation room with the propagation of distributions using the Monte Carlo method. The sensitivity analysis of the final uncertainty is also analyzed with regard to all the measured input values, such as the reverberation time, relative air humidity, air temperature, and the size of the sample. The obtained results show that the measurement uncertainty of the sound absorption coefficient measured in a 1:8 scale reverberation room is comparable to the measurement uncertainty of full-scale measurements and does not change significantly depending on the measurement conditions.