Relationships between noise sampling design and uncertainties in occupational noise exposure measurement

This paper presents the results of a study concerning the uncertainty related to the sampling of noise exposure. This study was carried out in two groups of workers, selected to include very different exposure situations in terms of the location of the workplace, the nature of the tasks carried out, and the variability of noise exposure from day to day. For each group, the noise exposure was measured continuously for approximately 80 hours in order to establish a reference suitable for estimating a daily noise exposure level from sampling. Various sampling designs were defined and applied to these data, characterized by the number of measurements, measurement duration, and the distribution of the samples among the data available for each group. The accuracy of each sampling design was estimated by Monte-Carlo simulations, i.e., reiterating the taking of a random sample 1000 times, to produce the distribution of all possible mean noise exposure levels and to deduce their 95% confidence interval, which was then used to estimate the uncertainty related to the noise sampling. This study has yielded information about the number of samples required to obtain a given accuracy that can be used as background material to revise the ISO 9612 standard.