Inter-Laboratory Test for the Assessment of Reproducibility Uncertainties on the Sound Power Levels of Earth-Moving Machines

The EC Directive concerning the limitation of noise emissions in the environment by equipment for use outdoors, requires that machines are labelled with the indication of the guaranteed sound power level. Many of these machines, like earth-moving machines, are also subject to noise limits. The guaranteed sound power level includes the uncertainties due to production variation and measurement procedures. While the Directive demands statistical safeguarding of the labelled sound power level, it doesn't specify any method of assessing uncertainties. For this reason, different formulas are nowadays commonly used in Europe, many of them requiring to assess the measurement uncertainties in terms of reproducibility standard deviation values. In order to obtain experimental estimates of reproducibility uncertainties associated to the sound power levels of excavators and dozers to be used for satisfying the provisions of 2000/14/EC Directive, two inter-laboratory tests were designed, each involving four different laboratories. This paper describes the results of these experiments and gives detailed information about their layout and the statistical procedure used for the analysis of the results.