Uncertainty analysis by a Round Robin Test of field measurements of sound insulation in buildings: Single numbers and low frequency bands evaluation -- Airborne sound insulation

The uncertainty of field measurements of a lightweight wall and a heavy floor was analysed by Round Robin Test (RRT), conducted in a full-scale experimental building at ITC-CNR. Each of the 9 teams involved in the I-RRT replicates the tests 5 times, for a total of 45 measurements, while the repetitions of reverberation time were 110. Both for sound insulation and reverberation time the main variations are in the low frequency range. The differences between D, R?, Dn and DnT and their reproducibility and repeatability standard deviations values were also analysed. The study is also focused on the single numbers evaluation: true value and uncertainty. Single numbers were evaluated in both narrow and extended range. The extension to low frequencies implies a variation in single number values that reaches its maximum in the case of X +Ctr in the extended range. This is because this index is the most influenced by low frequencies. Thus the measurement uncertainty at low frequencies has to be more deeply investigated, before including the low frequency range in the on-field measurements.