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SNR Vs NRR – Explained Noise Reduction Rating Chart

Understanding SNR (Single Number Rating) and NRR (Noise Reduction Rating) is key for choosing effective hearing protection. SNR, used in Europe, and NRR, prevalent in the US, both measure how well ear protection devices reduce noise in decibels but differ in testing methods. This distinction helps ensure you select the right protection based on your regional standards and noise exposure levels, enhancing safety in high-noise environments.

What Is SNR?

SNR gives you a specific rate of how much noise can be reduced. SNR stands for single noise rating. It also specifies how much the device in use is giving security to the hearer. It analyzes the protection rate of the same device too.

This evolves in a way that if you experience a product that gives 30 SNR, it can be said that the device can lower the noise up to 30 db.

It is mostly used in countries like the UK & USA. It is also used in the United Kingdom than in the United States of America. The most reasonably accurate value can be given through an SNR device.

What Is NRR?

NRR or noise reduction rating, qualifies as the term that eases the surrounding voices reaching their way to a person’s ear. As the term has the most meaning, it helps in reducing the excessive and loud sound waves that a person can bear up to an extent.

The number checks the amount of ease and its units in decibels. An average person can hear up to 20 db in a normal environment and 25 db in a noisy place. Most of the thorough tests are done in order to check whether a NRR device is working properly or not.

The object being tested mainly approves that the devices fit into the ear or not. When the ear protector is mixed with an ear socket, it is possible that NRR can be increased.

How Is NRR Measured?

Under the absolute and most fine circumstances, NRR is measured using ANSI/ASA S12.6-2016 standard, which is asked by organizations named EPA ( Environmental Protection Agency) & OSHA. As beneficial it is to compile the EPA to NRR , it is necessary that the device is tested in an certified provision. The methods for testing are properly described.

The person that is going to perform the test is required to be a professional from an authorized institution. Added to this is that he should also be able to perform the test. Before this the test for the significance of NRR was done with a reference to a method that was released in 1947, that required 10 people (human professional listener).

Everyone was asked to test the hearing protection device. And the number of frequencies that were used for testing were  9. The value that gave the approved NRR value was medium one.

ANSI S3.19 got replaced by ANSI S12.6 in 1984, and that got further updated in 2016. Two methods were introduced in this standard. One was called (Designated trained-subject fit). It was thought to know what is the utmost decrease that was given by a specific hearing protection device. Only a trained professional is required to get the proper value for this NRR test.

Only he can use it. The second was called (designated in experience subject fit), and this device can examine the maximum amount of noise decrease in a hearing protection device. It is not required for this to be tested by a professional. We can think that the second method is more likely to give near to real-world situations.

When the testing is complete, the device is given an EPA sticker with a specific NRR. People should choose hearing devices that are professionally tested by a proper organization and have a specific authorization sticker so that a person can be safe with the device.

An example can be taken as if an employee is continuously open to the elements of 100db, he is required a device that would decrease the noise level by 10db for him to bear, and in this way, the sound will be 90db.

What Is The Difference Between SNR And NRR?

The basic difference between NRR & SRR is that the decibel rate is slightly higher than the past rate. There has been no new formula made that changes the SNR into NRR, but it is said that the SNR value is 3db higher when compared to the frequencies of NRR.

The values differ because the frequencies taken are different. The tests done on both of the values are also not equal to each other. HML data is likely to be said to be patched up with an SNR device.

There are three primary frequency levels present High, Low, & Medium, which permits users to change the noise cancellation level depending on the noises they are experiencing in the background. It helps them to set a certain level.

If someone notices the possible difference between an SNR & NRR device, then it will be said that NRR ratings are lesser than SNR. These two terms can also be differentiated by the formulas used to calculate their average ratings.

Noise Reduction Rating Chart

Frequency In HZ 125 250 500 1000 2000 4000 8000
Mean Attenuation In dB 13.2 15.3 16.7 18.3 20.8 18.3 21.6
Standard Deviation in dB 2.5 2.3 2.2 3.1 2.8 2.0 2.9
APV in dB 10.7 13.0 14.5 15.2 18.0 16.3 8.7
H = 17, M = 16 dB, L = 14 dB, SNR = 18 dB
  • H: Average Attenuation Characteristics in the High Frequency Spectrum (> 2 kHz)
  • M: Average Attenuation Characteristics in the Mid Frequency Spectrum (0.5-2 kHz)
  • L:  Average Attenuation Characteristics in the Low Frequency Spectrum (<0.5 kHz)

Is SNR The Same As NRR?

No, it does not have any type of similarity, but the work they perform is slightly equal. A person cannot say that if he is given an NRR of 26db, he will have an SNR of 26. Both of them differ. The only difference between both is that NRR is not used in UK & USA, but SNR is definitely used in these places. Also, they are not identical.

Is the NRR Accurate?

No, NRR is not accurate enough. It can be too optimistic for the situation sometimes. The real sound level can be far less than it can appear on an NRR device from a hearing protection device. There can be a few reasons for that.

Application in real-world situations is different from the application in highly noisy factories where these devices are tested, this can be a reason why the NRR device label differs. Secondly, if by any chance a hair or piece of glass gets in the way or a person is not wearing a hearing protection device correctly, it can also affect the rate of the NRR device.

These minor mistakes often happened, so to avoid this, there was an urge to correct the real rate of an NRR device into something that is more accurate. The process that is done is called Derating.


There are a lot of dangers to a person if they are exposed to a high level of noise. Many methods can be used to protect the ears from getting damaged or getting the ear drum shatter.

Therefore, there are devices that can help you with that easily. The performance of hearing devices is dependent upon various factors as well, but it is said that SNR and NRR are both devices that can help in the reduction of extra noise in the surrounding. NRR and SNR help you to have a minor idea about up to which extent a device is capable of giving protection to the ears.

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