H & T PUBLICATION Work Health 2783-0756 2 1 2021 4-Year retrospective study hearing level among of Oil Refinery Company employees based on the results of medical examinations 11 16 EN Ramin Zare Saeed Roustaee Journal Article Introduction: The purpose of this study was to determine the volume of workplace noise and the process of changing the hearing threshold of workers in different units of a company oil refinery products over a period of 4 years. <br/>Methods: The type of historical study is retrospective. It was intended that the process of employee health be measured and studied according to the exposure of people to workplace noise and its impact on the level of physical health of employees during a period of 4 years. The sample size is 101 according to Cochran's formula. Data collection was done by registering the data in the periodic staff examination file in predetermined forms and by field method. <br/>Results: The results showed that at most frequencies in different years the mean hearing threshold has increased. For example, based on the results of the study, the mean and standard deviation of noise measured in the maintenance unit from 2014 to 2017 are equal to 88 (5) dB, 93 (9) dB, 94 (8) dB, and 96 (11) dB respectively, which indicates the increasing trend of sound level in the workplace. <br/>Discussion: Hearing loss as a consequence of workplace noise threatens the health of workers in the broadcasting company and therefore it is suggested that in addition to management controls, engineering controls be a priority for the HSE unit and the company's management. http://www.htpub.org/article/Work-Health/vol/2/issue/1/articleid/878