Protection


Noise Reduction Rating (NRR)


What's your number?

Hearing Protection Devices (HPDs) are rated based on the amount of noise reduction they provide. Through independent laboratory testing they are given a Noise Reduction Rating, or NRR. The NRR is expressed in decibels and is printed on the packaging. The higher this number is, the greater the noise reduction ability of the hearing protection device.

Since the NRR is determined under lab test conditions, it may not reflect 'real life' conditions. It is possible to insert and wear HPDs incorrectly, which can lead to a false sense of security. If used incorrectly, it is like wearing no hearing protection at all, so be sure to follow manufacturer instructions. Or better yet, check with your hearing health care professional for guidance.

Here are some examples of NRR and how it might be found on packaging:


Changes to NRR are coming...

Researchers continue to improve how hearing protection is designed and tested. The trend towards testing the NRR of different HPDs involves a 'Fit Test'. To do this, a small probe microphone is inserted into the ear canal and then the HPD is put into place. Then a signal is presented from an outside source and the probe microphone can measure how loud the sound is in the ear canal. This will give the researchers information about how effective the HPD is under 'real life' conditions, which is different from a standard laboratory condition.

When you see the numbers printed on the packaging of HPDs, keep in mind that the number printed will be higher than you would actually get under real-life use. Hopefully in the future there will be changes to the labeling of HPDs to take into account the results from the real-life measurements.

Due to the differences in NRRs obtained in the lab and in a real-life setting, there have been some standards set into place. If laboratory data are used then there has been a recommendation to derate the NRR by the following amounts as specified by NIOSH (National Institute of Occupational Safety and Health):

Hearing Protection Device Type Subtract from NRR (derate)
Earmuffs 25%
Formable Ear Plugs 50%
All other Ear Plugs 70%

The most important aspect of using HPDs is proper insertion and use. If used as directed you will be able to protect your hearing.

For more information about this please visit the Canadian Center for Occupational Health and Safety.

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