Case study: Noise risk assessment of workers at the mechanized mining face of coal mines.

An assessment of workers at the mechanized mining face of coal mines was conducted in China. The survey on the current status of subject exposure to noise of coal miners was administered by occupational health investigation and detailed record of work days. The noise dosimeter measurements of 211 workers were obtained, including coal cutting, supporting, transportation, crushing, and auxiliary (such as air pressure, pump, and maintenance). A total of 56.4% of the LEX,8h exceeded 85 dB(A), and the average 8-hour equivalent sound level of the workers at the mechanized mining face of these coal mines was 91.2 dB(A). Within the noise frequency from 500 to 6000 Hz, there was a "V" shift in the displacement value of hearing threshold. At the noise frequency of 4000 Hz, the hearing loss N50 (dB) of workers reached the maximum. The longer the exposure time, the higher risk both in high-frequency hearing loss and noise-induced deafness. The risk of high-frequency hearing loss reached the high-risk level at 25 years of work, while the risk of noise deafness reached the high-risk level after 30 years of work. In addition, the Pearson correlation coefficient between the noise exposure time and the risk of noise-induced hearing loss was high and positively correlated. The results show that the production noise hazards at the mechanized mining face of coal mine are relatively large. High levels of hazardous noise exposure are typical in coal mines. The noise exposure data can help to develop more feasible noise controls for the employer. [ABSTRACT FROM AUTHOR]