Exposure to Noise
Background - Legal Requirements and Recommendations
OSHA
The OSHA standard for occupational exposure to noise (29 CFR 1910.95) specifies a maximum Permissible Exposure Limit (PEL) of 90 dB, A weighted, slow response for a duration of eight hours per day. When employees are subjected to sound exceeding a Time Weighted Average of 90 dB, feasible administrative or engineering controls shall be utilized. If controls fail to successfully reduce sound levels below 90 dB, personal protective equipment must be provided.
In addition to the PEL, the OSHA standard also specifies an ‘Action Limit’ of 85 dB. If the Time Weighted Average (TWA) exceeds 85 dB for an 8 hr workday, the employer must implement a Hearing Conservation program for exposed workers.
The regulation, in calculating the PEL and Action Limit, uses a 5 dB exchange rate. This means that in order for a person to be exposed to noise levels of 95 dB, the amount of time allowed at this exposure level must be cut in half (4 hours) to be within OSHA's PEL. Conversely, a person exposed to 85 dB is allowed twice as much time at this level (16 hours) and is within his or her daily PEL.
NIOSH Recommendation
Considerable research indicates that the current OSHA legal requirement is not sufficient to prevent hearing loss in the majority of workers. Therefore, the National Institute for Occupational Safety and Health (NIOSH), in its Criteria for a Recommended Standard, proposed an exposure limit of 85 dB for 8 hours, 5 dB less than the OSHA standard. Also in contrast to the OSHA standard, NIOSH has recommended that a 3 dB exchange rate be used to calculate time-varying noise exposures (instead of a 5 dB exchange rate). Thus, a worker can be exposed to 85 dB for 8 hours, but to only 88 dB for 4 hours, or 91 dB for 2 hours.
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