The technological and industrial progress togetherwith the intensificationof vehicular traffic and the adoptionof
new social habits are the cause of an increasing noise pollution with possible negative effects on the auditory
system. This study aims to assess the noise exposure levels and the effects on the hearing threshold in outdoor
and indoor male workers of a big Italian city. The study was carried out on 357 outdoor male workers, exposed
to urban noise and on a control group of 357 unexposed indoor workers. Noise levels were measured in 30
outdoor and indoor areas. The subjects underwent tonal liminal audiometry in order to determine the value of
their hearing threshold. During their working activity, outdoor and indoor workers are exposed to different
noise levels LEXb80 dB(A). At mid–low frequencies (250–2000 Hz), the results show significant differences
in the average values of hearing threshold between the two groups in both ears and for all age classes; there
are no significant differences between the two groups at higher frequencies. The outdoor noise levels measured
are not usually ototoxic and the hearing loss at mid–low frequencies is not characteristic of the exposure to
industrial noise. For these reasons the Authors hypothesize that the results may be due to the combined effect
of the exposure to noise and to ototoxic air pollutants. The impairment of speech frequencies is disabling and
involves the risk of missed forensic recognition