Methods: A cross-sectional study was conducted on 543 police personnel who had undergone periodic
medical examination over a 12-month period. The diagnostic criteria for NIHL were (1) history of
occupational noise exposure, (2) bilateral hearing loss, (3) hearing loss of 25 dBA at 4,000 Hz in two
consecutive audiograms, and (4) no significant medical history affecting hearing. Severity of NIHL was
based on the World Health Organization grading