Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 6 3 1977 09 15 91 97 D. Parvizpour P. Meshgi 2015 10 03 The paper is based on a study conducted in three different industries on 84.4 on their employees to determine the effect of over all noise intensity, length of employment and rest periods among them. It was found that the mentioned factors have direct effect on the induced hearing loss among the exposed workers. High noise level and long period of employment adversely affect the hearing ability while the breaks taken during daily working hours have prevented the expected defect. https://ijph.tums.ac.ir/index.php/ijph/article/view/2722 https://ijph.tums.ac.ir/index.php/ijph/article/download/2722/2702