What does the SNR value on earplugs mean? How to read SNR, HML and dB

The SNR value of earplugs is a single number that shows how many decibels they reduce on average. If you subtract the SNR from the noise level in dB(C), you know roughly how loud the sound still is in your ear, in dB(A). A filter with SNR 24 brings 98 dB(C) down to about 74 dB(A) in this way. In practice, earplugs reduce less than on paper, which is why the British Health and Safety Executive (HSE) adds 4 dB to be on the safe side.

Besides the SNR, you often see the letters H, M and L. They give the attenuation for high, medium and low tones. Below, you can read how to read these values, with a worked example and a table of all the filters Audibling uses.

At Audibling, you choose the filter, and with it the SNR, yourself. A partner hearing care professional takes the impressions for your earplugs. The ear impressions are included in the price and you pay at the hearing centre.

What is the SNR value of earplugs?

SNR stands for Single Number Rating. It is the average attenuation across all frequencies, expressed in dB. The higher the number, the more the earplug reduces. Manufacturers of hearing protection are required to state the attenuation. You will find the SNR on the packaging or in the instructions for use.

In a custom earplug, the filter controls the attenuation. The custom earplug seals your ear canal, and the filter determines how much sound gets through. That is why Audibling gives the SNR for each filter, on our filter page and in the table further down. In a custom earplug, the actual attenuation can differ slightly, depending on the fit. Note that the number in a filter's name is not the SNR. The DR 20 grey, for example, has an SNR of 19 dB.

What do dB, dB(A) and dB(C) mean?

Sound is measured in decibels. According to the guideline on occupational hearing loss from the NVAB, the Netherlands Society of Occupational Medicine, this is a logarithmic scale, where every 3 dB extra means a doubling. So a few dB of difference matter. Two measurements are important for the SNR.

• dB(A) follows how our hearing perceives sound and counts low tones less. You use this number for the level in your ear and for the limits in the Dutch Working Conditions Decree (Arbobesluit).
• dB(C) counts low tones almost fully. You need this number to calculate with the SNR.

For sound with a lot of low tones, such as a compressor, a diesel engine or a press, dB(C) is clearly higher than dB(A). Read more about decibels in decibels and hearing damage explained.

A worked example with the SNR value

Say a noise measurement in a workshop gives 98 dB(C). You are considering a custom earplug with the DI 25 red filter, which has an SNR of 24. This is how to calculate with the HSE's SNR method.

1. Subtract the SNR from dB(C). 98 minus 24 is 74 dB(A). That is the estimate based on the lab value.
2. Add 4 dB for real-world use. 74 plus 4 is 78 dB(A). The HSE uses these 4 dB because hearing protection reduces less in real life than in the lab, for example if it does not fit properly.
3. Compare with the target. The HSE advises aiming for a level in your ear between 70 and 80 dB(A). At 78 dB(A), you are within that range.

This is how four filters work out in the same 98 dB(C) workshop.

Do you only know the level in dB(A)? Then do not simply calculate dB(A) minus SNR. With sound that has a lot of low tones, you would underestimate the sound in your ear, as the example below shows. If in doubt, have a noise measurement done in dB(A) and dB(C).

What do the HML values tell you?

The SNR is an average. The HML values show how the attenuation is spread across the tones.

• H is the attenuation for high tones, such as grinding, squealing brakes or hissing compressed air.
• M is the attenuation for mid tones, such as voices and a lot of machine noise.
• L is the attenuation for low tones, such as a diesel engine, a compressor or the bass in music.

If H, M and L are close together, the filter gives flat attenuation. Everything gets quieter without the character of the sound changing. You see this with the DM 25 black, at 19, 19 and 18 dB. If H is much higher than L, the filter mainly reduces the high tones. The DR 10 black reduces 11 dB for high tones and 3 dB for low tones.

Calculating with HML when there are a lot of low tones

With the HML method, you use both dB(A) and dB(C). The difference between the two shows how many low tones there are in the sound. The bigger the difference, the more the L value counts.

Here is an example using the HSE calculation method. Say a machine with a lot of low tones produces 95 dB(A) and 105 dB(C), a difference of 10 dB. With a DR 20 grey (H 19, M 17, L 14), the calculated attenuation then comes to 14 dB, equal to the L value. What remains in your ear is 95 minus 14, which is 81 dB(A), and with the real-world margin 85 dB(A). Anyone who had calculated 95 dB(A) minus SNR 19 would have arrived at 76 dB(A) and so would have been 5 dB out, even before adding the real-world margin.

SNR and HML for each filter

These are the values of all the filters Audibling uses, in dB, from the acoustic specifications of Dynamic Ear Company. The H, M and L values are below each filter name. The last column is a calculation aid. It gives the noise level at which, with that filter and the SNR method including the 4 dB real-world margin, you end up between 70 and 80 dB(A) in your ear.

The calculation aid does not replace a measurement or personal advice. For sleep, focus or sensory overload, it is not about a particular noise level but about how much quiet you are looking for. The DIM filters are level-dependent and meant for bangs from shooting, hunting and fireworks. With bangs, it is mainly the peak that counts, and the SNR says little about that. Read more in hearing protection against impulse noise. How the four filter series differ is explained in how the DR, DM, DI and DIM filters work.

Which SNR do you need?

The HSE gives a rule of thumb based on the noise level during a task. That table is not intended for sound with a lot of low tones, such as from presses, generators or boiler rooms. If the noise is at the bottom of a range, choose an SNR at the lower end, to avoid too much attenuation.

For work, the law also applies. Under the Working Conditions Decree, the employer must provide hearing protection when daily exposure is above 80 dB(A), and from 85 dB(A) wearing it is mandatory. With the hearing protection in, exposure must not be above 87 dB(A). Read all about the rules in what does Dutch law say about hearing protection at work?

Is a higher SNR always better?

No. More attenuation only helps if you would otherwise end up above 80 dB(A) in your ear. The HSE advises against ending up below 70 dB(A). That overprotection means you hear colleagues, traffic and warning signals less well, and it can make you feel cut off. If that makes you take your earplugs out now and then, you end up not being protected at all. According to BeSWIC, the Belgian knowledge centre for well-being at work, hearing protection that is worn properly only half the time lowers the average level by just 3 dB.

Why do earplugs reduce less in practice?

The SNR comes from a measurement in a laboratory. According to the NVAB guideline, many studies show that hearing protectors reduce less in practice than the instructions for use state. BeSWIC also writes that the attenuation in the workplace is usually much lower, for example because of badly inserted or damaged hearing protection. That is why the HSE calculates with a 4 dB margin. So with a custom earplug, a good fit is important. A fit check tells you whether it still seals well. Read more in how long do custom earplugs last?

Frequently asked questions

Is SNR 19 or 21 better?

SNR 21 reduces 2 dB more on average than SNR 19. Whether that is better depends on how loud it is around you. If SNR 19 already brings you between 70 and 80 dB(A) in your ear, SNR 19 is the better choice, because you will hear your surroundings better. If you stay above 80 dB(A) with SNR 19, SNR 21 helps. Also look at the HML values, because with a lot of low tones the L value counts more than the SNR.

How many dB does an earplug with SNR 20 reduce?

On average 20 dB, measured in the lab. For real-world use, the HSE calculates with 4 dB less, so about 16 dB. How much it is for you depends on the fit and the type of noise.

Can I calculate dB(A) minus SNR?

As a rough estimate for sound with few low tones, you can. With a lot of low tones, you would underestimate the sound in your ear. The SNR method is meant for a measurement in dB(C).

Which SNR suits a festival?

For most concerts and festivals, an SNR of 15 to 20 dB is enough. Music still sounds natural and your ears are protected. At Audibling, the DM filter suits this, with an SNR of 10 to 20 dB. Read more on earplugs for concerts and festivals.

Can I choose the right SNR myself?

The table and the worked example in this article will get you a long way. If you don't know how loud it is around you, have the noise measured or ask for advice when your ear impressions are taken. Not sure which filter to choose? Use the filter finder on our filter page.

Where can I find the SNR of my custom earplugs?

At Audibling, the SNR for each filter is on our filter page. Which other markings and codes you see on hearing protection is explained in what do PPE-3 and EN 352 mean?

Sources

• HSE, Controlling noise at work, L108, third edition 2021, appendix 1 on SNR, HML and the real-world margin (PDF) (accessed 4 October 2026)
• HSE, Hearing protection (rule of thumb for SNR by noise level, and overprotection) (accessed 4 October 2026)
• NVAB, Multidisciplinaire richtlijn Preventie beroepsslechthorendheid (guideline on preventing occupational hearing loss, PDF in Dutch) (accessed 4 October 2026)
• BeSWIC, FOD Werkgelegenheid, Gehoorbescherming (hearing protection, in Dutch) (accessed 4 October 2026)
• Arboportaal, Wat zegt de wet over lawaai op het werk? (what the law says about noise at work, in Dutch) (accessed 4 October 2026)
• Dynamic Ear Company, acoustic specifications (H, M, L and SNR) of the DR, DM, DI and DIM filters, as shown on our filter page