Relationship between cumulative noise exposure level and hearing loss induced by occupational noise

Objective To investigate the relationship between cumulative noise exposure (CNE) level and hearing loss induced by occupational noise.Methods In accordance with the data from ISO R1999,the relationship between hearing loss percentage and CNE was studied with statistical description method and three dimension curve graph.Results Hearing loss was not just a one-dimensional function CNE,but a twodimensional function of CNE (the intensity of noise exposure and the duration of noise exposure).Hearing loss curves presented flections at different intensities of noise exposure.When CNE hearing loss was approximately equal to the sum of noise exposure intensity and 7 dBA,hearing loss curves all presented flections.Hearing loss developed with the cumulated noise exposure level.When CNE was lower than the values of reflections,hearing loss worsened gradually and slowly with the intensity of cumulated noise exposure.Conversely,the opposite could be sighted in hearing loss.Conclusions The flexion pattern indicated that the hearing of those individuals could be worsened and even failed to recover permanently,once they were detected to have hearing loss induced by occupational noise exposure. Key words: Cumulative noise exposure;  Hearing loss;  Permissible noise exposure limits