Correlation between duration of noise exposure and severity of hearing loss

Background and Objective: Noise pollution is one of the commonest occupational and environmental health hazard. The extent of damage to hair cells is determined by the intensity of noise to which a person is exposed, and the duration of noise exposure [1] . Prolonged exposure to high intensity noise >85dB(A) or more, for eight hours can lead to permanent hearing loss. This exposure can be reduced significantly by using simple ear protection devices. NIHL can be easily prevented through the use of simple and economical tools, but are not used by people due to different reasons. 3 Our study aimed at determining the relation between the duration of exposure to loud noise on the severity of noise-induced hearing loss. The subjects of our study were train drivers working in an extremely noisy environment for long hours, without using any ear protection tool. Materials and Method: This study involved 60 subjects, who were all train drivers. They were working in an extremely noisy environment for more than eight hours a day for more than ten years. The responses to brainstem evoked response audiometry were recorded and evaluated for severity of hearing loss. Result: 60% subjects reported positive for sensorineural deafness. 18.3% of the subjects were having mild degree of hearing loss, 23.3% were having moderate degree of hearing loss and 18.3% were having severe degree of hearing loss. Conclusion: It was found that the duration of exposure to noise has a positive correlation with the degree of severity of hearing loss ( p <0.001), the intensity of noise being the same.