Effects of noise on peripheral hearing of bus drivers [a conventional and extended high frequency audiometry study]

ABSTRACT

Hearing threshold evaluation was assessed by pure tone audiometry for 100 subjects working as bus drivers, they were constantly exposed to buses noise for at least five years. Other causes for hearing impairment, either conductive or sensorineural, were excluded. The study group was compared with a control group of 30 normal hearing subjects. Elevation in hearing threshold was noticed in the study group, especially at high frequencies and the differences were statistically significant. Normal hearing was found in 43%, high frequency SNHL above 4 KHz in 14%, mild SNHL in 33%, moderate SNHL in 4% and moderately severe to severe SNHL in 6%. The degree of hearing loss was directly proportional to duration of noise exposure. The subjects with normal hearing sensitivity in the ordinary frequency range [0.25-8 KHz] showed statistically significant elevation in the extended high frequency range [9-IS KHz]. This signified the value of extended high frequency audiometry in the early detection of susceptibility of hearing to noise insult