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Noise Monitoring: A Sound Strategy
It depends on the local legislation, but in the United States, there are two different types of “action levels” or values. OSHA implemented a permissible exposure limit (PEL) of 90dBA for all workers for an eight-hour day. 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 over eight hours to minimize occupational noise-induced hearing loss.
The eight-hour exposure period is referred to as the Time Weighted Average (TWA). These exposures are all standardized to an eight-hour working day so that individuals with different exposure times and shift durations can all be compared to the same action values.
With the eight-hour averaged action levels, employers must measure representative samples of employees’ exposure to noise. To do this, an average measurement must be taken which is known as the LAVG, a logarithmic average. This is done with a handheld sound level meter or a noise dosimeter which can be work throughout the day. In the case of the noise dosimeter, as it is worn through the day it will display the eight-hour noise exposure.
If the workplace in which the sample is taken is continuously noisy—and will remain so over the workers’ shift—then the measurement can be taken over the course of a few minutes, as this is a representative average of the conditions throughout the day. If the noise level fluctuates throughout the day, longer samples must be taken to achieve a representative average when using devices such as a sound level meter. A noise dosimeter is a bodily worn device that can be worn to measure exposure during a working day, which is especially useful if the worker is mobile and therefore it becomes increasingly difficult to measure exposure using a handheld sound level meter.
Controlling Noise
Any sound over 85 decibels(dB) can damage hearing, meaning the operation of concrete mixers, forklifts, jackhammers, nail guns and masonry drills all pose a permanent risk to worker health if effective control measures are not put in place.
The hierarchy of controls should always be used with hearing protection being the last resort, or a first aid measure until noise can be controlled at the source. They are listed from the most to least effective and include elimination, substitution, engineering controls, administrative controls and personal protective equipment (PPE).
This article originally appeared in the September 2024 issue of Occupational Health & Safety.