Relationship between Noise Induced Occupational Hearing Loss and Cumulative Noise Exposure in Workers of Hydropower Station

Objective To analyze the occurrence and development rule of occupational noise-induced hearing loss,and find their relationship with cumulative noise exposure(CNE).Methods Pure tone threshold of workers and environment noise were monitored.Their CNE and related indicators were calculated.Results When CNE increased from(97.5±5.4)dB(A)year to(102.4±2.9)dB(A)year,the incidence of speech frequency and high frequency hearing loss raised from 4.6% and 11.5% to 10.3% and 28.7% respectively.There was statistical significant difference in each frequency hearing threshold increase especially in high frequency(P0.01);hearing threshold increase was correlated to the basic hearing threshold(P0.01).The incidence and severity of occupational noise-induced hearing loss were correlated with CNE and the threshold was 100 dB(A)year.Conclusions The CNE of exposed workers should be controlled;abnormal hearing threshold of workers especially the threshold in high frequency should be found as early as possible.Once it is found,the worker should be removed from the job post according to related regulation.