Measurement Uncertainty in the Determination of the Sound Absorption in a Reverberation Room at Low Frequencies

Both for the resonance absorber and for the broadband absorber having a large absorption capacity at low frequencies, the values of the sound absorption coefficient as measured in a reverberation room will depend considerably on the positioning of the sound source. For some types and arrangements of absorbers, the 95% confidence ranges for mean values of absorption coefficients are determined which will result when the loudspeaker position is varied. The breadth of these ranges can amount to 40% of the mean value. If one averages in a suitable way over the position of the sound source just as is done for the microphone used in the measurements, the limits of scatter about the mean value may be narrowed. The uncertainty of measuring the simple mean value still remains unsettled.