Relationship between sample size and variation of means for personal noise exposure in weaving workers / 中华预防医学杂志

<p><b>OBJECTIVE</b>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.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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).</p><p><b>CONCLUSION</b>The sample size in personal noise exposure measurement guideline could be selected from four to eleven.</p>

Relationship between impulse noise and continuous noise inducing hearing loss by dosimeter measurement in working populations / 中华预防医学杂志

<p><b>OBJECTIVE</b>To compare the dose-response relationship differences between impulse noise exposure workers and continuous noise exposure workers in prevalence of noise inducing hearing loss using dosimeter measurement.</p><p><b>METHODS</b>Thirty-two mechanical workers in a workshop were selected as impulse noise group and 163 textile workers in a textile factory as continuous noise group. SH-126 dosimeter was used to measure A weighted equal sound level of eight hours (L(Aeq.8 h)) during full working duration with equal energy rule for the selected workers. The cumulative noise exposure (CNE) was calculated by L(Aeq.8 h) and noise working years with equal energy rule for each worker. Hearing thresholds were measured by audiometer by routine method and adjusted by age and gender with GBZ49 - 2002. Hearing loss was diagnosed by GBZ49 - 2002 for each worker.</p><p><b>RESULTS</b>CNE of impulse noise group [(103.2 +/- 4.2) dB (A) .year] was found lower than the continuous noise group [(110.6 +/- 6.0) dB (A) .year] by significance, P < 0.05. The hearing loss prevalence of impulse noise group (68.8%) was similar as continuous noise group (65%) without significance, P > 0.05. Strata analysis showed the hearing loss prevalence in 100 - 104 dB (A) .year and 105 - 109 dB (A) .year of impulse noise group was double than that of continuous noise group (76.9%, 90.9% vs 30.4%, 50.0%), P < 0.05. The chi-square test showed a relationship between CNE and hearing loss prevalence that was in high significance (P < 0.01) in both impulse noise group and continuous noise group. Logistic regression model showed the dose-response relationship curve of impulse noise group was left shift and sharp slope.</p><p><b>CONCLUSION</b>The damage of impulse noise on hearing loss was much more than that of continuous noise according to equal energy rule of dosimeter data.</p>