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1.
Article in Chinese | WPRIM | ID: wpr-960418

ABSTRACT

The existing measuring methods of noise exposure on the basis of equal energy hypothesis are applicable to Gaussian noise while not fully applicable to non-Gaussian noise. Studies have shown that temporal structure (kurtosis) combined with noise energy has the potential to quantify non-Gaussian noise exposure effectively. However, there is no unified measuring method adopting this joint metric. In this paper, the measuring method of non-Gaussian noise exposure based on kurtosis adjustment was introduced, detailing measurement indicators, adjustment schemes, applicable objects, instrument requirements, and measurement steps. Adjusting the exposure duration of cumulative noise exposure (CNE) by kurtosis or adjusting the equivalent continuous A-weighted sound pressure level (LAeq) by an adjustment coefficient based on animal or population studies can more accurately quantify workers' exposure to non-Gaussian noise and improve the underestimation of hearing loss caused by non-Gaussian noise. A large number of population studies are warranted in the future to verify the effectiveness of these two adjustment schemes.

2.
Article in Chinese | WPRIM | ID: wpr-960420

ABSTRACT

Background Equivalent continuous A-weighted sound pressure level is not appropriate for evaluating the risk of non-steady noise exposure, and need to be corrected by noise time-domain structure, but the correction method and its applicability need to be discussed. Objective To validate the application of the kurtosis-adjusted normalization of equivalent continuous A-weighted sound pressure level to a normal 8 h working day ( LAeq,8 h) in assessing noise-induced hearing loss (NIHL), and to improve the methods for assessing occupational hearing loss associated with different types of noise. Methods Audiometric and shift-long noise exposure data were acquired from a population(n=2 466) of screened workers exposed to noise between 70 dB(A) and 95 dB(A) from 6 industries in China. The cohort data were collapsed into 1 dB(A) bins, and the average kurtosis and noise-induced permanent threshold shifts at 3 kHz, 4 kHz, and 6 kHz (NIPTS346) within 1 dB(A) were calculated respectively. According to the existing correction method, the adjustment coefficient λ was calculated by multiple regression, and LAeq,8 h was corrected by λ (L'Aeq,8 h). The entire cohort was divided into K1 (≤10; steady noise), K2 (10~50; non-steady noise), and K3 (>50; non-steady noise) groups based on mean kurtosis levels. Predicted NIPTS346 was calculated using the ISO 1999 model for each participant and the actual measured NIPTS346 was corrected for age and gender. The underestimated NIPTS346 was the difference between the values of estimated NIPTS346 and the corresponding actual NIPTS346. To validate the applicability of L′Aeq,8 h in evaluating NIHL, the correlation between L′Aeq,8 h and HFNIHL, and the mean difference between real NIPTS346 and estimated NIPTS346 were analyzed. Results The adjustment coefficient λ was determined at 5.43. The results of multiple logistic regression analysis showed that the relationship between L'Aeq,8 h and HFNIHL increased from 6.6% to 9.6% after the kurtosis adjustment. The DRR of LAeq,8 h and HFNIHL showed that the percentage of HFNIHL decreased after the adjustment of kurtosis in the non-steady noise groups, and the regression lines of the non-steady noise groups approached that of the steady noise group. The R2 of the K2 group increased from 0.935 3 to 0.986 3, and the R 2 of the K3 group increased from 0.905 6 to 0.951 6. Under the un-adjusted condition, the NIPTS346 underestimation for the K3 group was significantly higher than that for the steady noise group (t=−3.23, P=0.001). After the LAeq,8 h was adjusted by kurtosis, the NIPTS346 underestimation decreased significantly in the three kurtosis groups (K1: t=6.78, P<0.001; K2: t=14.31, P<0.001; K3: t=11.06, P<0.001). There was no significant difference in the degree of underestimation between the three kurtosis groups (K1 vs K2: t=−0.22, P=0.830; K1 vs K3: t=−1.40, P=0.205) as the curves of the three kurtosis groups were nearly overlapped. Conclusion The kurtosis-adjusted LAeq,8 h can effectively estimate the hearing loss associated with non-steady state noise.

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