Noise Exposure and Hearing Status among the Registered Locksmiths in Tehran, Iran

Noise is one of the most common workplace hazardous agents that can cause permanent hearing damage. Workers in many industries are usually exposed to noise levels with high risks of hearing loss. Accordingly this research aims to study the noise exposure and haring status of registered locksmiths who are exposed to harmful effects caused by several factors, such as key making machines loud noises. This study has been carried out in 33 key workplaces in Tehran capital city of Iran. In order to eliminate the effects of background noise, two different measurements were carried out in the same field conditions by taking in and out of key making machines. The overall sound level and octave band of noise analysis of the key making machine, during the process of Right and Left Shift Gears by considering the background noise level during off time of the machine was determined using ISO 9612 standard method. Hearing threshold of locksmiths is also determined using the NIOSH standard method. Based on results, average of right and left groove keys scraping processes and background noise levels were 92.9, 96.2 and 66.5dBA respectively. The mean noise exposure time of locksmiths was 0.2 h/day. So, the amount of the workers noise equivalent level was found to be 77.63 dBA which is lower than the ACGIH threshold limit values. The results of audiometric tests also showed no significant hearing loss among locksmiths, something can be explained by their low noise exposure levels. It is suggested to assess hearing response of the workers by other methods like ABR.