MEASUREMENT UNCERTAINTY IN BUILDING ACOUSTICS

In general, uncertainties should preferably be determined following the principles laid down in ISO/IEC Guide 98-3, the Guide to the expression of uncertainty in measurement (GUM:1995). According to current knowledge, it seems to be impossible to formulate these models for the different quantities in building acoustics. Therefore, the concepts of repeatability and reproducibility are necessary to determine the uncertainty of building acoustics measurements. This study shows the uncertainty of field measurements of a lightweight wall, a heavy weight floor and a façade with a single glazing window that were analyzed by a Round Robin Test (RRT), conducted in a full-scale experimental building at ITC-CNR (Construction Technologies Institute of the National Research Council of Italy). The single number quantities and their uncertainties were evaluated in both narrow and extended range and it was shown that including or excluding the low frequencies leads to very significant differences, except in the case of the sound insulation of façades. In building acoustics it is also very important to know the confidence level of a measurement, which was standardized for the first time in the Italian Standard on the acoustic classification of building units. This study also shows an application of the sampling included in the Italian Standard on a serial type building of 47 building units. It was found that the greatest variability is observed in the façade and it depends on both the great variability of the window's typologies and on workmanship.