The reverberation-room method, which assumes a diffuse sound field, has long been used for various standardized room-acoustical measurements-i.e. absorption coefficient, source power level, transmission loss. However, unsatisfactory opinions regarding the accuracy of the method, especially at low frequencies, have been reported over the years. This might be due to a deviation from the assumed diffuse-field concept, which is very challenging to implement from an application point of view. To

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... stigate the problem and find a solution, a number of reverberation rooms of different sizes and shapes have been studied; their capacity to approximate a diffuse sound field is analyzed by means of descriptors like cutoff frequency, spatial uniformity of sound pressure and reverberation time, degree of linearity of temporal decay curves. Results obtained with the help of a numerical finite-element-based modal approach are discussed; in particular, the effect of different room sizes and shapes on the measurement accuracy is explained. Based on these findings, recommendations are proposed regarding the sizes and shapes of reverberation rooms that will give better field diffuseness and, hence, better measurement accuracy.