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Hearing: Loss and Protection – Part I

- October 26, 2017 by Mike Pettit (View all posts by Mike)

Have you ever had to lean closer to someone and/or raise your voice to communicate due to high noise levels? If so, there’s a risk of hearing loss if you are exposed to the noise levels for extended periods of time and without the appropriate hearing protection.

The best way to prevent hearing loss is to reduce noise at the source by engineering a noise control solution – an example could include isolating the noise source with an enclosure. Unfortunately, engineering out the noise is not always realistic or feasible.

If a person is exposed to sounds averaging greater than 90 dBA (the unit of measurement is decibel, which is the unit used to measure the intensity of a sound) without hearing protection for eight hours per day, hearing loss will most likely result. As the volume increases, the amount of time you can safely stay in the noise environment decreases.

Here are some loudness/time facts to consider:

    • 95 dB – damage will occur after four hours of exposure, per day.
    • 100 dB – damage will occur after two hours of exposure, per day.
    • 105 dB – damage will occur after one hour of exposure, per day.
    • 110 dB – damage will occur after 30 minutes of exposure, per day.
    • 115 dB - damage will occur after 15 minutes of exposure, per day.
    • 120+ dB - damage occurs almost immediately.
    • If you have to speak in a loud voice to be understood, background sound is probably in excess of 90 dBA. For example, most portable stereo music systems produce sound in the range of 95-108 dBA at level four, and in excess of 115 dBA at level eight.

      Once engineering controls have been implemented, yet noise levels still exceed permissible levels, what else can we do to protect ourselves and our workers from hearing loss?

      Hearing protection devices, or HPDs, are common within the workplace. As with all forms of personal protective equipment, HPDs should always be the last resort to mitigate the potential for hearing loss.

      Another thing to consider is that the effectiveness of hearing protection depends on the protectors being properly fitted and worn – when this is not the case, the intended protection is subsequently reduced.

      When calculating whether a Hearing Protector will be effective, we have to consider the Noise Reduction Rating (NRR) for your specific hearing protector.  Because people are all different and because the HPD may not be properly worn, OSHA requires that the NRR value be ‘adjusted’ in order to determine if it will be effective in your workplace.  My colleague Brian discussed performing proper calculations in his recent blog.

      Often times, people make the mistake of believing earplugs with a 25 dB NRR will reduce noise levels by 25 dB. Using the above calculating method, the reduction afforded by the earplugs would only be 9 dB.

      In summary, personal hearing protection should be a last resort once all engineering controls have been implemented. Once the level of required protection is determined, the appropriate hearing protection should then be properly fitted and worn by all affected workers.

       

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