The Uncertainty Declaration of Building Acoustics Measurements: How to Select the Uncertainty of Reproducibility from Inter-Laboratory Tests

This paper deals with the standard deviation of reproducibility obtained from multiple Inter-Laboratory Tests (ILTs), whose average values were standardized in ISO 12999-1. The reproducibility obtained in this way is intended to be used for the declaration of uncertainty in test reports of building acoustics measurements. Therefore it is necessary that the declared uncertainty be representative of all the specimens, or products, that could be tested. This paper demonstrates that the new standard deviation σR95, introduced for the first time in ISO 12999-1, leads to an overcoverage with respect to the desired 95% coverage probability. Moreover, two other methods are presented, the former based on a Bayesian analysis and the latter on random variance and fixed mean, to demonstrate that the reproducibility standard deviation σR, where the reproducibility variance σ2 R is the mean value of the variances of all the ILTs included in ISO 12999-1, is the natural choice for the declaration of uncertainty.