Study on the threshold limit of cumulative noise exposure of hearing impairment

Objective To investigate the auditory critical threshold limits of cumulative noise exposure of occupational hearing loss according to the relationship between cumulative noise exposure and hearing impairment rate in speech and high frequency. Methods The auditory threshold data of (1 435) steel workers were analyzed with Logistic regression models by SPSS software. Results The impairment rate of hearing threshold levels in speech and high frequency was increased with the level of noise exposure. Logistic regression analysis was conducted for the cumulative noise exposure and prevalence in speech frequency hearing impairment, the results indicated that hearing threshold levels were significantly associated with the cumulative noise exposure. The predictive curve indicated that the critical value of cumulative noise exposure be 100 dB(A) in speech frequency hearing impairment. Conclusions This value is consistent with the national regulation for occupational noise exposure and it may act as a warning index in assessing risk of hearing loss of individual occupational noise exposure.