Uncertainty of façade sound insulation in buildings by a Round Robin Test

The uncertainty of field measurements of a façade was evaluated by a Round Robin Test (RRT) conducted in a full-scale experimental building at the Construction Technologies Institute of the National Research Council of Italy (ITC-CNR). Each of the 9 teams involved in the RRT replicated the tests 5 times, for a total of 45 measurements, while reverberation time was repeated 110 times. Both for façade sound insulation and reverberation time the main variations in the one-third octave bands were found in the low frequencies range. The study was also focused on the evaluation of single number quantities (SNQs) and their uncertainties. Single number quantities were evaluated in both narrow (from 100 to 3150 Hz) and extended (from 50 to 5000 Hz) range. Concerning the SNQs and their uncertainties, no significant differences were observed whether the low frequencies were included or not, unlike the case of airborne sound insulation (investigated in the first part of this study). The uncertainty results were compared with the relevant standards and with literature results. Based on these comparisons, it was highlighted that the standard deviation of reproducibility of façade elements is not adequately reflected in the ISO 12999-1 and further research is needed to specify the in situ standard deviation of reproducibility for façade elements.