[Evaluation of kurtosis on hearing loss caused by non-steady state noise in general equipment manufacturing industry].

Objective: To study the effect of occupational exposure to non-steady state noise on hearing loss in the general equipment manufacturing industry, and to explore the feasibility of applying kurtosis index to evaluate hearing loss caused by non-steady state noise. Methods: A total of 233 workers exposed to non-steady state noise in 6 general equipment manufacturing enterprises were selected as the observation group, and 237 workers exposed to steady noise in 4 textile enterprises were selected as the control group between 2012 and 2018. Personal normalized continuous A-weighted sound pressure level equivalent to an 8 h-working-day (L(Aeq, 8 h)) was determined by a noise dosimeter. Cumulation noise exposure (CNE) was calculated from L(Aeq, 8 h) and related working age, and the CNE was adjusted by using noise kurtosis (CNE' after adjustment) . Meanwhile, questionnaires and hearing loss tests were performed for all subjects. The changes in the threshold of high-frequency hearing and the incidence of high-frequency hearing loss caused by noise in the two groups were compared before and after the adjustment of the kurtosis of CNE. The correlation between CNE and the incidence of high-frequency hearing loss before and after kurtosis adjustment was analyzed. Results: There was an difference between the 3000-8000 Hz hearing threshold of workers in different CNE groups (P<0.05) . logistic regression analysis showed that CNE was a risk factor of high-frequency hearing loss for workers in the observation group (OR=1.189, P<0.05) , and trend Chi-square test showed that the incidence of high-frequency hearing loss increased with CNE levels (χ(2)(trend)=34.415, P<0.05) .Before the kurtosis adjustment, in the CNE 95~<110 dB (A) ·year level group, the incidence of high-frequency hearing loss and the high-frequency hearing threshold in the observation group were significantly higher than those in the control group (P<0.05) . After kurtosis adjustment, there was no significant difference in the incidence of high-frequency hearing loss between the observation group and the control group in each level group (P>0.05) . The correlation between CNE after kurtosis adjustment and the incidence of high-frequency hearing loss was better than that before adjustment (after R(2) adjustment >before R(2) adjustment) . Conclusion: The effect of non-steady state noise on high-frequency hearing loss of workers in general equipment industry increases with the increase of CNE, and the effect of non-steady state noise on high-frequency hearing loss of workers is greater than that of steady noise. CNE' can be used to evaluate the hearing loss caused by non-steady state noise.

[Dose-response relationship between noise kurtosis and noise-induced hearing loss].

Objective: To analyse the dose-response relationships between the kurtosis metric of noise and noise-induced hearing loss (NIHL) and study the role of kurtosis in the evaluation of NIHL associated with non-Gaussian noise. Methods: From January 2012 to December 2017, a total of 1869 workers in seven manufacturing industries were selected as the study subjects. The basic data of the workers were investigated by questionnaire, personal noise waveform was collected for a long time, and pure tone hearing threshold was tested. The 8-hour continuous equivalent A sound level (L(Aeq, 8 h)) , cumulative noise exposure (CNE) and kurtosis structure indexes were calculated. The dose-response relationships between kurtosis and NIHL were analyzed by stratification analysis method, which controlled the influence of CNE, L(Aeq, 8 h), exposure duration, age and sex on hearing loss using high-frequency noise-induced permanent threshold shift (NIPTS(346)) and high-frequency noise-induced hearing loss (HFNIHL) as outcome indicators. Results: When CNE was <90 dB (A) ·year and ≥100 dB (A) ·year, NIPTS(346) in the extremely high kurtosis group was significantly greater than that in the Gaussian kurtosis, low kurtosis and medium kurtosis group (P<0.05) . In the workers exposed to L(Aeq, 8 h)<85 dB (A) and ≥94 dB (A) , NIPTS(346) in the extremely high kurtosis group was significantly greater than that in the Gaussian kurtosis group (P<0.05) . Among workers under the age of 50 or male workers, NIPTS(346) in the extremely high kurtosis group was significantly greater than that in the Gaussian kurtosis, low kurtosis and medium kurtosis group (P<0.05) . Kurtosis was positively correlated with NIPTS(346) (r=0.121, P<0.05) . When CNE was <100 dB (A) ·year, the detection rate of HFNIHL increased with the increase of kurtosis level (P<0.01) . Logistic regression analysis showed that kurtosis was an important influencing factor for HFNIHL (OR=1.321) . Conclusion: Kurtosis has a dose-response relationship with the detection rate of HFNIHL in noise exposed workers, and noise kurtosis is an influencing factor of NIHL.