布机挡车工个体噪声暴露样本含量与等效声级均数变异的关系

目的探讨个体暴露抽样例数与抽样数据均数变异的关系,为制订个体噪声暴露测量规范提供科学依据。方法以布机车间挡车工个体噪声暴露测量数据8 h等效连续A声级(LAeq·8h)为分析对象,采用可重复随机抽样方法从个体噪声暴露数据中抽取一定数量的样本,计算均数。每次抽样1-15个,抽样1000次时,分析抽样LAeq·8h均数变异的规律。结果抽样例数较少时,LAeq·8h均数的最大值、最小值、第95百分位数(P95)和第5百分位数(P5)曲线向均数靠拢的速度较快,抽样例数增大时变化趋于平缓。每次分别抽样1、4、7和11例时,LAeq·8h均数P95和P5的差值分别为7．40、3．30、2．44和1．85 dB,抽样4、7、11例时的LAeq·8h均数P95和P5差值分别约为抽样1例时的1／2、1／3和1／4。结论纺织厂布机挡车工每组的个体噪声暴露测量抽样例数在4-11例为宜。

Relationship between sample size and variation of means for personal noise exposure in weaving workers

OBJECTIVE: To explore the relationship between sample size and variance of means for personal noise exposure in weaving workers as to contributing evidence for establishing personal noise exposure measurement guideline. METHODS: A personal noise exposure measurement database from a group of weaving workers was used in the randomized re-sampling data analysis. The sampling cases were one number selecting from one to fifteen at each randomized re-sampling procedure. The randomized re-sampling was one thousand times from original personal noise exposure measurement database to get one thousands of re-sampling database. One thousands of L(Aeq.8 h) mean were calculated by re-sampling databases. The variation of randomized re-sampling means was analyzed for different re-sampling numbers. RESULTS: The change for narrow trend of maximum, minimum, 95 percent number, 5 percent number of L(Aeq.8 h) mean was faster when randomized re-sampling number was smaller in variation vs randomized re-sampling number curve analysis. After that, the change for narrow trend of L(Aeq.8 h) mean was smooth for increasing the randomized re-sampling numbers. The 95% - 5% of L(Aeq.8 h) mean was about half for randomized re-sampling four cases (3.30 dB) vs one case (7.40 dB), and about one third for seven cases (2.44 dB), and about one fourth for eleven cases (1.85 dB). CONCLUSION: The sample size in personal noise exposure measurement guideline could be selected from four to eleven.