Personal noise exposure evaluation in mining activities and inherent uncertainties

The assessment of personal noise exposure is necessary both for the prevention of hearing damage and for resolving insurance or legal disputes where it is required to establish whether a causal link exists between noise exposure and chronic hearing impairments. Legislation in many countries requires the evaluation of daily or weekly exposure in noisy work environments. Noise exposure levels often vary significantly over time, For this reason the measurements can be affected by a large degree of uncertainty, both when determined directly, through personal sampling for the entire duration of the working shift, and indirectly by brief measurements carried out in specific fixed positions. Short and long term exposure levels are essentially influenced by noise fluctuations and the amount of time spent in a given position, The effect of these parameters is shown for work tasks typical of the extractive industry, determined by means of a statistical analysis of real data drawn from measurement campaigns performed over the last ten years. It is shown that exposure level populations are well represented by normal or log-normal statistical distributions. Thus measurement campaigns can be designed so as to obtain statistically significant results and perform appropriate data analysis for prediction purposes.