SNR Versus NRR

LAST UPDATED: September 17th, 2021 | BY: Stacy Merci

In order to select hearing protection which is well suited for our needs there are numerous simplified and numerical attenuated ratings that have been conceived. The purpose of these ratings is to inform us buyers exactly by how many decibels it is, that a sound or noise shall be reduced when this noise or sound is heard using hearing protection, be it ear defenders or ear plugs.

Some of the most commonly known attenuation ratings are SNR and NRR. Both of these ratings are denoted by decibel numbers, or DB. It is believed that the higher the decibel number is, the more protection from noise it is going to provide the user with.

If you wish to know more about exactly what it is that these ratings constitute and how these ratings differ from one another, read on.

What is NRR?

NRR

NRR is essentially a noise reduction standard that is used widely across the USA, and it mentions the level of noise reduction that is offered by a hearing aid, with this noise reduction level being stated in the form of decibels.

For instance, if you buy a set of ear defenders whose NRR is 30 decibels, then the noise reduction capacity of this hearing aid will be by thirty decibels, in ideal circumstances.

A rigorous series of tests are conducted by hearing protection manufacturers to determine the NRR of a hearing protection device, with the testing procedure being quite clinical in nature, at times. The testers usually ensure that the subject of the tests have fitted the hearing protection onto their ears properly.

What this often entails, is that the results of the tests that are conducted, can often overstate the actual performance that is rendered by hearing protection devices.

It is possible for the NRR to be increased when ear defenders are combined with ear plugs. According to Cooper Safety, this can be done by adding approximately 5 decibels to the item that is characterized by a higher NRR, instead of summing up the value of two NRR ratings.

Thus, ear plugs that have NRR of 30 decibels and ear defenders that have NRR of around 27 decibels will have a combined NRR of 35 decibels when clubbed together.

What is SNR?

SNR is an acronym that stands for single noise rating, and it is extensively used in the countries of the European Union, as a standard that demonstrates the attenuation level of hearing protection aids. SNR is far more commonly used in the United Kingdom than in the USA, with an NRR number being featured on hearing protection products here, only if these have been imported in from the USA.

An approximate estimate of the type of noise reduction that is provided by a hearing protection product, is given by SNR in the format of decibels. When the SNR is 20, this implies that the noise reduction level that is offered by the hearing protection device that has this SNR, will be by about 20 decibels.

SNR

If an obvious difference between NRR and SNR ratings is to be identified, then this will be that the SNR ratings are usually a couple of decibels higher than the NRR ratings.

For determining the SNR rating, this is paired with yet another attenuation rating, which is known as HML rating. The latter provides the user with a sufficient understanding of the attenuation that is offered by a hearing protection device at various frequencies, low, medium, and high.

This makes it possible for the wearer to pick up protection at a time when the noise levels of the environment that he is in fall in a specific area of the frequency spectrum.

A downside associated with the SNR rating is that it does not provide an accurate representation of how effectively a hearing protection device can perform in real world situations. The noise reduction levels are not likely to be sufficient if the hearing protection is loose in terms of fitting.

It is recommended on the part of experts that both NRR and SNR are to be derated if an accurate figure is to be arrived at for noise reduction levels in real world circumstances rather than in ideal conditions.

It is recommended on the part of the health and safety representative of the UK government for instance, that a derating of four decibels ought to be applied to an SNR number. What this entails is that ear defenders that are characterized by an SNR rating of 30 will be expected to offer noise reduction of approximately 26 decibels in real world conditions.

What is the Difference between SNR and NRR?

Some of the specific differences between SNR and NRR lie in the type of formulas that are utilized to calculate these ratings. NRR is evaluated between 125 hertz and 8000 hertz while SNR is evaluated between 63 hertz and 8000 hertz.

A figure of 100 decibels is taken as reference level when calculating SNR while in the case of NRR, 107.9 decibels is taken as a reference level, and from which 3 decibels is subtracted to arrive at an accurate understanding of the NRR.

Noise Reduction Rating Chart

Highest NRR Ear Plugs

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Conclusion

To sum it up, NRR and SNR are two unique standards that have been developed to measure attenuation of hearing protection products. NRR is the standard that is used in the USA while SNR is the standard that is used in the EU and in the UK.

Both ratings aim at providing hearing protection users with a correct notion of the noise reduction levels that they can expect when using the hearing protection device, in real world conditions.

The actual performance of the hearing protection aid is, however, dependent on various other factors as well, given that both the NRR and the SNR have been designed to bring about a reduction in noise attenuation complexities to a single digit.

The noise environment in which the hearing protection product is going to be used and how well fitting it is, are factors that need to be taken into consideration, to determine the performance of the same, over, and above, the SNR or NRR ratings of the product.