Noise exposure assessment with task-based measurement in complex noise environment

<正> Background Task-based measurement （TBM） is a method to assess the eight-hour A-weighted equivalent noiseexposure level (LAeq.8h) besides dosimeter. TBM can be better used in factories by non-professional workers and staffs.However, it is still not clear if TBM is equal or similar with dosimeter for LAeq.8h measurement in general. This studyconsidered the measurement with dosimeter as real personal noise exposure level （PNEL） and assessed the accuracy ofTBM by comparing the consistencies of TBM and dosimeter in LAeq.8h measurement.Methods The study was conducted in one automobile firm among 387 workers who are exposed to unstable noise.Dosimeters and TBM were used to compare the two strategies and assess the degree of agreement and causes ofdisagreement. Worker's PNEL was measured via TBM for noise; the real PNEL was also recorded. The TBM for noisewas computed with task/position noise levels measured via sound level meter and workers' exposure informationcollected via working diary forms （WDF） filled by participants themselves. Full-shift noise exposure measurement viapersonal noise dosimeters were taken as the real PNEL. General linear model （GLM） was built to analyze the accuracy ofTBM for noise and the source of difference between TBM for noise and real PNEL.Results The LAeq.8h with TBM were slightly higher than the real PNELs, except the electricians. Differences of the twovalues had statistical significance in stamping workers （P <0.001）, assembly workers （P=0.015） and welding workers（P=0.001）. The correlation coefficient of LAeq.8h.8h with TBM and real PNELs was 0.841. Differences of the two results weremainly affected by real PNEL （F=11.27, P=0.001）; and work groups （F=3.11, P<0.001） divided by jobs and workshopswere also independent factors. PNEL of workers with fixed task/position (（86.53±8.82） dB（A）) was higher than thosewithout (（75.76+9.92） dB（A）) （7=8.84, P <0.01）. Whether workers had fixed task/position was another factor on theaccuracy of TBM for noise （F=4.36, P=0.038）.Conclusion TBM for noise has acceptable accuracy on workers' PNEL measurement. The accuracy is affected by jobcategories, workshops and variability of task/position. TBM for noise can yield a relatively conservative result of worker'sPNEL in most cases, so it can be used to measure and assess workers' real PNEL.