NoiseCurbThe NRR on hearing protectors is a lab number that overstates real protection. For a quick OSHA-style estimate with dBA noise, subtract 7 from the NRR and halve the result: an NRR 33 plug gives about 13 dB. NIOSH now recommends individual fit testing. Choose by loudness, duration, need to hear and comfort, and fit foam plugs deeply.
The number printed on a pack of earplugs is not the protection you will get in your ear. That single misunderstanding is behind most bad choices in hearing protection. This guide walks you through choosing protection by asking four questions, then shows how to estimate the protection you will really get.
The rating on the box: what NRR means
In the US, the Environmental Protection Agency requires every hearing protector to carry a Noise Reduction Rating (NRR), measured in a lab under ideal fitting conditions. Typical foam earplugs are rated in the high 20s to low 30s; many earmuffs are in the 20s.
The lab result assumes a trained, perfect fit. Real people fit protectors less well, so real-world protection is usually lower, sometimes much lower.
Estimating real protection
OSHA's standard includes a simple method for noise measured in dBA (the usual kind):
- Subtract 7 from the NRR. This corrects for how the rating is measured.
- For a safety margin, halve the result. OSHA applies this 50% factor when judging whether protection is adequate.
For an earplug rated NRR 33: (33 − 7) = 26, then 26 × 50% = about 13 dB of real protection. That is a long way from 33.
Choosing protection: four questions
1. How loud is it?
Roughly: yard tools and power tools often run in the 90s to over 100 dBA at the operator's ear, concerts can exceed 100 dBA, and firearms produce sudden peaks far above that. The decibel chart lists common sources.
2. How long will you be exposed?
Safe time drops fast as sound gets louder. Under the NIOSH recommendation, 85 dBA is acceptable for 8 hours, 94 dBA for about 1 hour and 100 dBA for about 15 minutes. Longer exposure needs more protection.
3. Do you need to hear speech, music or alarms?
Too much protection has its own risks: you may miss warnings or conversation. This is where the type matters.
4. What will you actually wear?
The best protector is the one you wear correctly the whole time. Comfort, fit with glasses or a helmet, and heat all matter.
The main types compared
| Type | Strengths | Watch out for |
|---|---|---|
| Foam earplugs | High protection when fitted well, cheap | Must be rolled and inserted deeply; poor fit is very common |
| Pre-molded reusable plugs | Washable, quick to insert | Fit varies by ear size |
| Earmuffs | Easy to fit correctly, good for on-and-off use | Glasses arms and hair break the seal; hot in summer |
| High-fidelity (musician) earplugs | Lower the volume evenly so music and speech sound natural | Lower attenuation than foam; not for very loud machinery |
| Electronic earmuffs | Let quiet sounds through, block loud peaks | Cost; batteries |
| Plugs plus muffs | For very loud noise such as firearms | See the rule below |
Wearing plugs and muffs together
Two protectors do not add up. OSHA's guidance is to take the more protective device, work out its derated protection as above, and add 5 dB for the second device. For example, OSHA's own worked example gives a plug rated NRR 29 about (29 − 7) ÷ 2 = 11 dB, and adding muffs brings the estimate to about 16 dB. Doubling up helps, but modestly.
Fit is everything
For foam earplugs:
- Roll the plug into a thin, tight cylinder with clean fingers.
- Pull the top of your ear up and back with the opposite hand to straighten the canal.
- Insert the plug well into the canal.
- Hold it for 20 to 30 seconds while it expands.
A well-fitted foam plug should sit mostly inside the ear. If most of it sticks out, protection is far lower. With earmuffs, check that glasses arms, hats or hair are not breaking the seal around the cushion.
A quick check: with protectors in, your own voice should sound louder and deeper, and outside noise should drop clearly.
Myths worth dropping
- "NRR 33 means 33 dB quieter." Real protection is usually much lower.
- "Two protectors double the rating." The estimate adds about 5 dB.
- "Noise-cancelling headphones are hearing protection." Only products tested and labeled with an NRR count as protectors.
The short version
- The NRR is a lab number. For a quick real-world estimate: subtract 7, then halve it.
- NIOSH now recommends individual fit testing over fixed label reductions.
- Choose by loudness, duration, need to hear, and what you will actually wear.
- Plugs plus muffs add about 5 dB, not double.
Related reading: noise-induced hearing loss, earplugs for sleeping and hearing protection for mowing and power tools.
Questions people ask
Does NRR 33 mean 33 dB quieter?
No. It is a lab rating. OSHA's method for dBA noise subtracts 7 and applies a 50% safety factor, so NRR 33 is about 13 dB in practice.
Can I wear earplugs and earmuffs together?
Yes, for very loud noise. OSHA estimates the combination by adding about 5 dB to the derated protection of the better device.
Are noise-cancelling headphones hearing protection?
Only if they are tested and labeled with an NRR as a hearing protector.
Which is better, plugs or muffs?
Foam plugs can give more protection if fitted well; muffs are easier to fit correctly. The best one is the one you wear properly the whole time.
Sources
- Methods for estimating the adequacy of hearing protector attenuation (1910.95 App B) · OSHAchecked
- Occupational noise exposure · OSHAchecked
- Hearing protection device · Wikipediachecked
- Hearing protector use and care · 3Mchecked
- Criteria for a recommended standard: occupational noise exposure · NIOSHchecked
This guide is general information, not medical advice. For sudden hearing loss, pain, discharge, dizziness or ringing in one ear only, see a doctor promptly. Medical disclaimer.