noise induced hearing loss among workers of an iranian axial parts factory, 2009

the aim of the present study was to examine the rate of noise induced hearing loss in a group of punching and cutting section and other occupational groups workers and its relation with sound pressure levels, age and work history. this descriptive, cross-sectional study included 245 workers of the punching and cutting section and other occupational groups of an iranian axial parts factory in 2009. hearing threshold limits were measured in both ears at 250, 500, 1000, 2000, 40000 and 8000 hz with ac40 clinical audiometer. in addition, sound pressure levels measured with iec 60651 sound level meter at dba in 148 stations of workers task with niosh standard method. at places where the sound pressure levels were upper than 85 dba, the frequency analysis was also done. the mean age of the population under study was 34.61 8.76 years and mean work history was 11.74 4.21 years. equivalent sound level (leq) was at least 98.1dba and at the most 115.7dba. in addition, result indicated nihl t was ranged 17.45 to 56/67 db. according to regression analysis, with assumption of a fixed work history, there is a mean decrease of 0.21 db in nihl t for every decibels of increase in equivalent sound level (leq) and with assumption of a fixed equivalent sound level (leq); there is a mean decrease of 0.42 db in nihl t for every year of increase in work history ( p < 0.05). nihl of varying degrees in workers of an iranian axial parts factory starts at 4000 hz and is then directed towards upper or lower frequencies.