INSIGHT INTO NOISE ASSESSMENT
Noise, or unwanted sound, is one of the most common occupational hazards in American workplaces. The National Institute for Occupational Safety and Health (NIOSH) estimates that 30 million workers in the United States are exposed to hazardous noise. Exposure to high levels of noise may cause hearing loss, create physical and psychological stress, reduce productivity, interfere with communication, and contribute to accidents and injuries by making it difficult to hear warning signals.
OSHA sets legal limits on noise exposure in the workplace. The limits are based upon a worker's time weighted average (TWA) over an 8-hour day. The permissible exposure limit (PEL) for noise is 90 dBA for all workers for an 8-hour day. Further, OSHA has established an Action Level of half the PEL (or 85 dBA for an 8-hour shift). It should be noted that this Action Level, unlike the PEL, adjusts for long duration work shifts. (i.e. the Action Level for a 10-hour shift is equivalent to 83.4 dBA, while it is 82.1 dBA for a 12-hour shift).
The preferred method to determine compliance to the OSHA PEL and Action Level is through personal noise dosimetry, using a small dosimeter that is clipped at the shoulder of employees and worn for the duration of the shift. This meter records the dose, average noise, and TWA and other relevant information for download and comparison.
Typically for spot measurements, noise mapping, and community noise, a sound level meter such as the one pictured at the left will be used.
These type of meters are much more accurate than dosimeters, and can also measure multiple frequencies simultaneously (commonly referred to as 1/1 and 1/3 octave bands), which is a requirement for some city/county noise ordinances for nuisance noise, and can also be useful for deploying engineering controls. This meter is also preferred for mapping activities.
Example Work Product – Noise Assessment
A typical facility will have noise monitoring data in hand, as OSHA requires that noise monitoring be performed whenever there is a potential for exposure to exceed 85 dBA.
However, the data from previous noise monitoring often will be aged. Processes change, equipment is replaced/upgraded, and the overall noise present within a facility can slowly change over time. The recommended approach is a two-tiered strategy, targeting both personal noise dosimetry and a background noise level assessment. First, a group of representative employees will be selected for noise dosimetry. For this activity, the employees will wear a noise dosimeter on their shoulder for the duration of the work shift. The Action Level adjusts for extended duration shifts, and as such, it is recommended that monitoring occur for the entire shift. An example of the typical results generated by this service is shown below:
As can be seen from the example table above. Thirteen (13) of the fifteen (15) work positions have been found to exceed the OSHA Action Level. This means that, at minimum, these employees should be provided with hearing protectors, and undergo annual audiometric testing and training. Two (2) of the fifteen (15) work positions exceed the OSHA PEL. Hearing protection should be required for these employees, and the feasibility of engineering or administrative controls should be considered to reduce noise at this location to below the PEL.
20 February 2019
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