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Assessment of occupational noise exposure: methodology, measurement error, evaluation criteria

机译:职业噪声暴露评估:方法,测量误差,评估标准

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摘要

BACKGROUND: Occupational noise exposure can be monitored directly by personal sampling or indirectly, by area sampling. Personal sampling is performed using an integrating sound level meter, worn by the worker while performing his/her job. When area sampling is used, measurements need to be made in all locations where a typical worker stays while performing his/her tasks; the respective partial lengths of exposure need to be accurately monitored, and the time-weighted average sound level of the measured noise levels must be calculated. OBJECTIVES: Current regulations identify three different thresholds, corresponding to different types of action, but they do not propose any standard criteria to decide whether a threshold has been exceeded. Defining standard procedures to assess occupational noise exposure and identifying such thresholds is crucial. METHODS: Using empirical data collected in the field, the effects are illustrated of the number of sampling locations and of the partial lengths of exposureon area sampling measurements, and the effects of duration of noise exposure on both area and personal samplings. RESULTS: When dealing with area samplings, an accurate definition of both sampling locations and partial lengths of exposure is crucial. When arbitrary decisions are taken in selecting sampling locations and/or establishing partial lengths of exposure, spatial changes in noise level and operator' displacements while performing his/her tasks may affect results. Sampling for less than the duration of noise exposure is the major contributor to measurement error, particularly under conditions of unpredictable variation in noise level. In fact, as noise level in the non-monitored time fraction is unknown, measurement error cannot be determined. We estimate that, even under the most favorable circumstances, sampling should last not less than 40% of the duration of a given noise-generating occurrence, for repeated measurements to be dispersed within a range not wider than that generated by the instrumental error. Inter-daily variability is another important aspect in personal noise exposure evaluation. This is a general occurrence, whose effects cannot be controlled by simply considering weekly instead of daily exposures. Results of an investigation, covering about 60 different jobs within a primary aluminum plant, show an inter-daily variability in noise exposure greater than 5 dBA in about 75% of cases. CONCLUSIONS: Personal sampling, when correctly performed and covering the total duration of exposure, provides the most reliable result as it integrates noise over all locations where the worker actually stays while performing his/her tasks, and over the total length of time spent in each task. We propose extending personal sampling to the total duration of actual noise exposure as the standard procedure for monitoring daily personal noise exposure, and valid for the majority of work places. When the range of daily noise exposure includes one regulatory threshold, corresponding to a given type of action, we propose as a standard decision criterion to refer prudentially to the upper 95% confidence limit of the LEP,d arithmetic mean. Such criterion would allow to standardize procedures and decision methods, with the prospect of further improvements in the assessment of exposure to noise.
机译:背景:职业噪声暴露可以通过个人抽样直接监测,也可以通过区域抽样间接监测。使用集成的声级计进行个人采样,该声级计在工人执行工作时要佩戴。当使用区域抽样时,需要在典型工人执行任务的所有位置进行测量;需要精确地监控各自的部分曝光长度,并且必须计算所测噪声水平的时间加权平均声级。目标:现行法规确定了三种不同的阈值,分别对应于不同类型的行为,但是它们没有提出任何标准标准来确定是否已超过阈值。定义评估职业噪声暴露的标准程序并确定此类阈值至关重要。方法:使用现场收集的经验数据,说明了采样位置数量和区域采样测量的部分暴露长度的影响,以及噪声暴露持续时间对区域和个人采样的影响。结果:在进行区域采样时,准确定义采样位置和部分暴露长度至关重要。当在选择采样位置和/或确定曝光的局部长度时做出任意决定时,噪声水平的空间变化和操作员在执行其任务时的位移可能会影响结果。小于噪声暴露持续时间的采样是导致测量误差的主要因素,尤其是在噪声水平发生不可预测的变化的情况下。实际上,由于未知时间段内的噪声水平未知,因此无法确定测量误差。我们估计,即使在最有利的情况下,采样也应持续不少于给定噪声产生持续时间的40%,以便将重复测量分散在不大于由仪器误差产生的范围内。日间变异性是个人噪声暴露评估中的另一个重要方面。这是一个普遍现象,其影响无法通过简单地考虑每周而不是每天的暴露来控制。调查结果涵盖了一家铝厂的约60个不同工作,结果表明,在大约75%的情况下,每天的噪声暴露差异大于5 dBA。结论:正确执行个人采样并覆盖暴露的总持续时间,可以提供最可靠的结果,因为它可以将工人在执行任务时实际居住的所有位置以及在每个工作所花费的总时间上的噪声综合起来任务。我们建议将个人采样扩展到实际噪声暴露的总持续时间,作为监控日常个人噪声暴露的标准程序,并且适用于大多数工作场所。当每日噪声暴露的范围包括与给定类型的动作相对应的一个调节阈值时,我们建议作为一种标准决策标准,审慎地参考LEP,d算术平均值的95%置信上限。这种标准将使程序和决策方法标准化,并有望进一步改善对噪声的评估。

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