بررسی ارتباط بین صدا و افت شنوایی در کارگران کارگاه نورد ذوب آهن اصفهان

One of the most impairment aspect in occupational health is the study    of noise induced hearing loss (NIHL) in noise exposed workers. The study    was carried out to find out relation and a model between noise exposed    workers and NIHL in 1997.           To determine NIHL in the worker in loom-650, 45 workers having no    confounding factors were choosen. All the study population were examined    using audiometer.           Result showed the SPL range was 70-105 dBA. The average of work    experience were 10.3±3.5 and age 37.4±6.7 years. Correlation coefficient    between job history and NIHL in the left ear was 0.7099 and  in the right ear    was 0.7127. The Pearson’s correlation coefficient between left and right ear    was positive and  equal to 0.69. The mean of NIHL between right and left    ear was 14 dB which the  regression model predicts the limit of hearing loss    in left ear is 4.5 years and in right ear is 3.8 years. Although the results    showed loss of hearing begins in right ear, but left ear had more hearing loss    with increasing of experience years. The danger limit for hearing of these    workers (based on 25 dB loss), for left ear and right ear  were after 17 and    20.7 years of work experience respectively.           To prevent serious impairment in the workers hearing, it is suggested to    consider the limit of 17 year's occupancy in forging as a base for changing    the occupancy.