Physically, there is no difference between sound and noise. Sound is a sensory perception and noise corresponds to undesired sound. By extension, noise is any unwarranted disturbance within a useful frequency band (NIOSH, 1991). Noise is present in every human activity, and when assessing its impact on human well-being it is usually classified either as occupational noise (i.e. noise in the workplace), or as environmental noise, which includes noise in all other settings, whether at the community, residential, or domestic level (e.g. traffic, playgrounds, sports, music).
OSHA sets legal limits on noise exposure in the workplace. These limits are based on a worker’s time weighted average over an 8 hour day. With noise, OSHA’s permissible exposure limit (PEL) is 90 dBA for all workers for an 8 hour day. The OSHA standard uses a 5 dBA exchange rate. This means that when the noise level is increased by 5 dBA, the amount of time a person can be exposed to a certain noise level to receive the same dose is cut in half.
The National Institute for Occupational Safety and Health (NIOSH) has recommended that all worker exposures to noise should be controlled below a level equivalent to 85 dBA for eight hours to minimize occupational noise induced hearing loss. NIOSH has found that significant noise-induced hearing loss occurs at the exposure levels equivalent to the OSHA PEL based on updated information obtained from literature reviews. NIOSH also recommends a 3 dBA exchange rate so that every increase by 3 dBA doubles the amount of the noise and halves the recommended amount of exposure time.
Effect of Occupational Noise:
Exposure to high levels of noise can cause permanent hearing loss. Neither surgery nor a hearing aid can help correct this type of hearing loss. Short term exposure to loud noise can also cause a temporary change in hearing (your ears may feel stuffed up) or a ringing in your ears (tinnitus). These short-term problems may go away within a few minutes or hours after leaving the noisy area. However, repeated exposures to loud noise can lead to permanent tinnitus and/or hearing loss.
The noise monitoring is conducted using Integrating and Logging Sound Level Meter (ISLM), 01dB Metravib, Quest 2900 UL, Quest SoundPro, or Bruel&Kjaer 2238 (based on availability of the equipment). The ISLMs can use ‘A’, ‘C’ or ‘Z’ weighting for noise measurements and can also use various ranges for measurements in order to appropriately monitor varying noise levels.
The ISLM will be placed on a tripod with its microphone pointing towards the equipment / plant. Noise levels will be monitored as A-Weighted Equivalent Continuous Noise (Leq). In addition, Minimum (Lmin) and Maximum (Lmax) Noise Levels will also be monitored. The monitored values will be logged into the ISLM memory, which will be downloaded upon completion of monitoring.