Effects of aircraft noise on hearing and auditory pathway function of airport employees

The effects of aircraft noise on hearing and auditory pathway function were studied in 112 airport employees, both by audiometry and brainstem auditory evoked potentials (BAEPs) to evaluate cochlear function and to verify the possibility of retrocochlear involvement. Employees were divided into five groups according to their daily jobs. Group A was made up of 23 maintenance workers, Group B of 20 firemen, Group C of 24 policemen, Group D of 34 airline ground staff, and Group E of 14 civil servants. The typical audiogram pattern of noise-induced hearing loss (NIHL) was a dip at 3 or 4 kHz and moderate hearing loss in the frequency range of 6 to 8 kHz. The results of audiograms in this study revealed the prevalence rate of high-frequency loss in all employees was 41.9%. The incidences of NIHL were highest in the groups of maintenance workers (65.2%) and firemen (55.0%), who are almost continuously exposed to aircraft noise. As for the BAEPs, both click threshold and latencies showed that the impairment was most severe in the groups of maintenance workers and firemen. There was prolongation in central conduction time, shown mainly in intervals of I-V and III-V. This suggests that involvement of the central auditory pathway, especially between the pons and midbrain, is present. In summary, the degree of auditory damage coincided with job patterns. Furthermore, damage of both peripheral cochlear organs and the central auditory pathway by high-frequency aircraft noise exposure was confirmed.