Last week I talked about the basic categories of hearing protectors. Today I would like to talk about how we determine which product to pick based on the products’ individual “rating”. Before looking at ratings of products, we need to first understand how sound is measured.
The “decibel” (dB) is a logarithmic unit of measurement designed to convert sound pressure changes into a more convenient number to work with. Simply put, our ears are capable of hearing sound pressures over an enormous range of ratios. The decibel scale helps to keep this complex formula more simple to understand.
0 dB is the threshold of hearing and 130 dB is the threshold of pain (The absolute highest recorded measurement ever is about 190 dB…enough to make you instantly deaf within seconds). Sound level monitors and dosimeters are used to help identify sound levels in a workplace so that decisions can be made with regards to
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Is hearing protection required?
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Which hearing protection device should we use?
While OSHA requires mandatory hearing protection once a 90 dB TWA (time-weighted average) is reached, most safety professionals understand that an 85 dB TWA (or action level) is a much safer level to require hearing protection. The 85 dB action level is when all workplaces are required to implement a Hearing Conservation Program to evaluate and monitor potentially excessive noise concerns in a given workplace.
Every earplug/muff sold has a NRR (noise reduction rating) associated with it and it indicates the amount of potential protection that device will give in a noisy environment. Even though a higher NRR is intended to indicate a greater noise reduction capability, the reduction obtained in actual use is affected by the protector size, fit, and style as well as the user motivation and training. A safer, more realistic estimate of protection can be obtained by reducing the labeled NRR by 50%.
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