What is SNR?
Every pack of hearing protection shows an SNR value, for example SNR 28 dB. This page explains what the number means, how it is measured and how to use it to choose the right hearing protection for concerts, sleep, work or your child.
SNR: one number for attenuation
SNR stands for Single Number Rating. It states by how many decibels a hearing protector reduces the sound level on average when worn correctly. It is determined in a standardised laboratory test to EN ISO 4869-2 with several test subjects and forms part of the EN 352 certification, the European standard for hearing protectors. A protector with SNR 28 dB reduces a level of 100 dB to roughly 72 dB on paper.
The calculation is an approximation. The lab uses the C-weighted level, whereas in daily life you usually only know the A-weighted value from an app or meter. The SNR is also an average across many people. If the protector fits you worse than it fitted the test subjects, it attenuates less. So the SNR is a comparison value between products, not a guarantee for your individual case.
H, M, L: attenuation by frequency
Next to the SNR you will find three more values: H for high frequencies (roughly above 2,000 Hz), M for mid and L for low frequencies (below 500 Hz). The SCHALLWERK Kiddies, for example, have SNR 28 dB with H 33 / M 25 / L 18 dB. High sounds such as whistling, screaming or hissing are attenuated more than low sounds such as bass or engine rumble. That is true of almost all hearing protectors, because low frequencies are physically harder to block.
For your choice this means: for bass-heavy noise such as concerts or engines, the L value says more than the SNR. For high-pitched noise such as circular saws or screaming children, the H value counts.
APV and the table on the packaging
The instructions often contain a table with frequencies from 63 to 8,000 Hz and three rows: mean attenuation, standard deviation and APV (Assumed Protection Value). The APV is the mean attenuation minus the standard deviation. It describes the attenuation that 84 percent of wearers achieve at least. For everyday use the SNR is enough, but the table shows at which frequencies a product is strong or weak.
Which SNR for which purpose?
More attenuation is not automatically better. If you want to hear the alarm clock while sleeping, talk to colleagues in the workshop or enjoy the music at a concert, you need protection that lowers the level without blocking everything. As a guide using SCHALLWERK products: Sleep+ for sleeping has SNR 22 dB, Music+ for concerts SNR 18 dB with even attenuation across the spectrum, Strong+ for everyday use SNR 23 dB, and the Work+ earmuffs for loud machinery SNR 33 dB. For children there are the Kiddies with SNR 28 dB and the Kids+ earplugs with SNR 29 dB, for babies the MINI+ with SNR 24 dB.
Rule of thumb: take the level of your situation minus the SNR. If the result is below 80 dB, you are well set for the typical duration of that situation. Typical levels of common noise sources are listed on the page Noise sources and their loudness.
SNR and NRR: do not mix them up
Products from the USA often show an NRR value (Noise Reduction Rating). It is measured differently and is usually several decibels lower than the SNR of the same product. Always compare SNR with SNR. All SCHALLWERK hearing protectors are tested to EN 352; the declarations of conformity are available under Declarations of conformity.
The SNR only applies with a correct fit
The laboratory value assumes that earplugs sit deep enough in the ear canal and that earmuff cups fully enclose the ear. Hair, glasses frames or an earplug that is too small quickly cost 5 to 10 dB. How to fit hearing protection correctly is explained on the page Tips on wearing and care. Which size suits you or your child is covered by the size guide.
Frequently asked questions
Is a higher SNR always better?
No. For sleep, concerts and conversations a medium SNR around 23 dB is often more comfortable because speech and music stay intelligible. A high SNR such as 33 dB is meant for machinery noise and construction sites.
What does SNR 28 dB mean for children?
The Kiddies reduce a level of 100 dB to roughly 72 dB on paper. The value applies to EN 352-1:2020 with a correct fit on a head circumference of 52 to 60 cm.
Can I add SNR values when combining earplugs and earmuffs?
No. Double hearing protection adds about 5 dB in practice, not the sum of both values.
Where do I find the SNR of my SCHALLWERK products?
On the product page, on the packaging and in the declaration of conformity. The values are identical in all languages of the shop.