Guide to Earplugs and Decibel (dB)
Loudness of sound is expressed in decibel (dB) values. A high value means a loud sound. A sound with 40dB is quiet and a sound with 90dB starts to be loud.
How strong earplugs are is also expressed in decibel (dB) values. For earplugs the decibel value means, that the earplug reduces the loudness by that amount of decibel.
Wearing a 20dB earplug in a noise environment of 100dB results in 80dB sound in your ears.
The more dB an ear plug has, the quieter it will be when the plug is worn.
Hearing damage may occur, if the ear is exposed to specific level of noise for more than a specific amount of time. The table below shows loudness in dB, how to recognize it, and how long it is safe to experience it.
| Loudness dB | Description | How long it is safe per day |
|---|---|---|
| 30 | whisper | – |
| 60 | normal conversation | – |
| 80 | > 8 hrs | |
| 85 | 8 hrs | |
| 88 | 4 hrs | |
| 91 | subway, passing motorcycle, loud and noisy restaurant | 2 hrs |
| 94 | a comparatively quiet club | 1 hr |
| 97 | 30 min | |
| 100 | hand drill | 15 min |
| 103 | clubs, must shout to talk with another person | 7 min 30s |
| 106 | 3 min 45s | |
| 109 | concerts and louder clubs, must shout very loud directly at another person to talk | 1min 53s |
| 112 | 56s | |
| 115 | loud car horn nearby | 28s |
| 120 | loud concerts or loud clubs, verbal communication only barely possible even when shouting directly into others’ ears, jet plane takeoff | 9s |
| 130 | < 1s | |
| >140 | gunshot, fireworks |
In the above table the safe values for the exposure time are taken from recommendation for occupational noise exposure of the National Institute for Occupational Safety and Health (NIOSH). The table is only an approximation of what is how loud. However, it is clearly visible that almost all clubs, concerts, and loud work environments are significantly above 85dB and are very likely to cause hearing damage without hearing protection.
As visible from the table, as soon as the noise is above 85-90dB, the time you can stay safe without a risk of incurring hearing damage is very low. Many clubs have sound levels above 100dB, which gives you even less than 15 minutes of safe exposure time.
The earplug should get the exposure level down to a safe zone, which is at or below 85 dB. This means that a weak earplug with 15 dB sound reduction is sufficient for a quieter club with 94 dB noise, because 79 is below 85dB (94-15=79).
The same earplug would not be sufficient in a loud club with 106db if you wanted to stay longer than 2 hours. This is because 91 dB (106dB-15dB=91dB) is only safe for about 2 hours
The decibel data for each brand of earplugs is sometimes written on the packing or available on the internet. There are different numbers for each frequency and an overall number labeled as NRR (Noise Reduction Rating – US) or SNR (Single Number Rating – Europe).
Use the lowest number of any frequency mean, NRR, or SNR. If the NRR is provided, then it is usually the lowest number. Use this lowest number to make your calculation for whether the earplug is sufficient for your use or not.
But also pay attention to your ears when wearing the plugs. If you’re ears hurt, you fell pain, or are uncomfortable due of the noise, then the earplugs are probably too weak for you and you should use stronger plugs.
Example 1:
The Bilsom 303 foam earplugs have the following sound reduction properties according to the American Standard
| Measurment Standard: | ANSI S.3.19-1974 | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| NRR: | 29 dB | ||||||||
| Frequency Hz | 125 | 250 | 500 | 1000 | 2000 | 3150 | 4000 | 6300 | 8000 |
| Mean Attenuation dB | 34.4 | 35.0 | 36.2 | 35.9 | 36.4 | 38.9 | 39.8 | 42.6 | 43.0 |
| Standard Deviation dB | 3.4 | 4.2 | 3.8 | 3.0 | 2.9 | 3.0 | 3.2 | 4.2 | 4.1 |
And the measurments of the same ear plug according to the European Norm
| Measurment Standard: | EN 352-2:2002 | |||||||
|---|---|---|---|---|---|---|---|---|
| SNR: | 33 dB | |||||||
| H: | 32 dB | |||||||
| M: | 29 dB | |||||||
| L: | 29 dB | |||||||
| Frequency Hz | 63 | 125 | 250 | 500 | 1000 | 2000 | 4000 | 8000 |
| Mean Attenuation dB | 28.4 | 37.3 | 37.9 | 39.1 | 36.0 | 34.6 | 42.5 | 46.4 |
| Standard Deviation dB | 6.4 | 9.0 | 9.2 | 9.7 | 7.9 | 4.6 | 4.9 | 4.7 |
| Assumed Protection dB | 22.0 | 28.3 | 28.7 | 29.4 | 28.1 | 30.0 | 37.6 | 41.8 |
So which number to use? The lowest of NRR, SNR, or frequency mean. In this case, this is 28.4dB from the European Standard.
In a loud club with 113dB of sound and wearing the Bilsom earplugs, this results in 84.6dB for the ears (113dB – 28.4dB). This is below 85dB and therefore should be save for a whole 8 hours. 113dB is already a loud club.
If it get louder than that, let’s say 123 dB, then the Bilsom 303 gives 94.6dB (123dB-28.4dB). This is only safe for a little less than an hour. But few places for entertainment, should be in this range.
There are a few stronger earplugs available than the Bilsom 303, but somewhere around NRR 33 the air gets thin.
If you work in a loud environment above 115dB, then you should seriously consider using earmuffs in addition to the earplugs.
Example 2:
The Erasers Musician’s Hi-Fi Earplugs has written on the packing as a selling point “Reduces up to 19dB of dangerous high frequency sounds”. A decibel table is also contained in the packing and reads as follows:
| Measurment Standard | ANSI S.319-1974 | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| NRR | 5 | ||||||||
| Frequency Hz | 125 | 250 | 500 | 1000 | 2000 | 3150 | 4000 | 6300 | 8000 |
| Mean Attenuation dB | 2.7 | 3.2 | 1.2 | 6.7 | 14.9 | 19.2 | 16.7 | 14.8 | 11 |
| Standard Deviation dB | 3.5 | 3.1 | 6.5 | 4.2 | 5.3 | 4.0 | 3.7 | 48 | 3.8 |
According to the rule of the lowest number to use, this would be the 1.2 dB. So in an environment of 100 dB you get your sound exposure down to 98.8 dB (100dB-1.2dB=98.8dB), which is almost no difference.
Even when using the NRR of 5dB for the calculation, it results in 95db (100dB-5dB=95dB) which is still very far above the safety threshold of 85dB.
This example shows why it is important to look at the detailed dB tables or the NRR (which are usually both measured and calculated according to standardized rules).
The Earasers earplugs only provide enough safety if the environment is just a tiny little bit above 85dB.
Example 3:
If you attend a loud rock concert and want to stand in front of the speaker, you may have 120dB of environment noise or even more. The strongest earplugs have around 30dB of noise reduction. So you will still be left with at least 90dB, which gives you a maximum of 2 hours time.
If you have read until here, then you have got the most important point of this article. It is to estimate how loud your environment is in dB and then deduct the dB of your earplugs (usually the NRR) and the result must be at or below 85 dB. And if your ears hurt or you feel uncomfortable, then also use stronger ear protection.
If you are also interested in choosing earplugs that gives you a good sound quality and good speech recognition, then read the article on earplugs, decibel curves, and high sound quality. Not all earplugs are the same.
Or if you are interested in invisible earplugs, then read the article on invisible ear plugs and high sound quality.
Sources:
Safe exposure times:
The National Institute for Occupational Safety and Health (NIOSH). Occupational Noise Exposure – DHHS (NIOSH) Publication Number 98-126. Retrieved from http://www.cdc.gov/niosh/docs/98-126/ on May 14, 2016.
United States Department Of Labor – Occupational Safety & Health Administration.Occupational Noise Exposure. Retrieved from https://www.osha.gov/SLTC/noisehearingconservation/#loud on May 14, 2016.
Bilsom 303:
honeywellsafety.com. Instruction Manual – Bilsom 303/304 (global). Retrieved from http://www.honeywellsafety.com/Supplementary/Documents_and_Downloads/Hearing_Protection/Earplugs/4294986710/1033.aspx on May 14, 2016.
Earasors:
Virginia Tech. Hearing Protector Attenuation Test for Earasers High Fidelity Ear Plugs. Retrieved from http://docs.google.com/viewer?url=http%3A%2F%2Fcdn.shopify.com%2Fs%2Ffiles%2F1%2F0560%2F1421%2Ffiles%2FVTECH_ANSI_TEST.pdf%3F253&embedded=true on May 14, 2016. The Document is linked to by http://www.earasers.net/pages/specifications, also retrieved on May 14, 2016.
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Thank you for the detailed info!