What the NRR Label Shows
The label format comes from the US Environmental Protection Agency (EPA) rules for hearing protectors, 40 CFR Part 211. The primary label must show:
- The words "Noise Reduction Rating" and the NRR value in decibels for that model.
- The statement that the range of NRRs for existing hearing protectors is approximately 0 to 30, with higher numbers meaning greater effectiveness.
- The phrase "When used as directed".
OSHA describes the NRR as a laboratory-derived estimate of the attenuation a protector achieves. For earmuffs whose headband can be worn in different positions, the label must give the worst-case NRR.
The NRR is measured with continuous noise. EPA requires a warning that it may not be an accurate indicator of protection against impulsive noise such as gunfire, so compare shooting ear protection on more than the NRR alone.
How to Work Out the Level Under Your Earplugs
OSHA's technical manual gives the formula. It depends on how the noise was measured:
- Measured in dBC: subtract the NRR from the noise level.
- Measured in dBA: subtract the NRR minus 7 dB from the noise level.
OSHA's example: a workplace level of 100 dBA and earmuffs with an NRR of 19 dB give an estimated 100 − (19 − 7) = 88 dBA under the muffs.
A phone decibel meter reads in dBA by default, so use the 7 dB correction with its readings. For what the A means, see what dBA is.
Why Real Protection Is Lower Than the Label
OSHA says the NRR in most cases overstates the protection workers get. The lab test uses careful fitting that people rarely match in daily use, and OSHA cites studies in which roughly half of workers got less than 5 to 15 dB of attenuation without training.
So when deciding whether noise must be reduced at the source, OSHA also halves the corrected NRR. Its example: a worker at 98 dBA with protectors rated NRR 25 dB gets an estimated 98 − (25 − 7) × 50% = 89 dBA. For judging whether the protection itself is adequate, OSHA only subtracts the 7 dB, which gives 80 dBA.
NIOSH now recommends individual fit testing instead of adjusting the label. A fit test gives a Personal Attenuation Rating (PAR), an estimate of how much one person's protector reduces their noise exposure. NIOSH's 2025 science update replaced its 1998 advice to derate the NRR by protector type.
NIOSH's quick fit check: count aloud while cupping and uncupping your hands over your ears. With a good fit, your voice sounds the same either way.
Earplugs and Earmuffs Together
Wearing both does not add the two ratings. OSHA's method takes the higher NRR, subtracts 7 dB for a dBA reading, and adds 5 dB for the second protector.
OSHA's example: at 110 dBA, earplugs rated NRR 29 and earmuffs rated NRR 25 give an estimated 110 − [(29 − 7) + 5] = 83 dBA. Double protection adds only 5 dB.
NIOSH recommends earmuffs over earplugs for workers exposed to 100 dBA or more, or to impulse sounds.
NRR vs SNR
SNR, the single number rating, is the figure on hearing protectors sold in the UK and Europe. The UK Health and Safety Executive (HSE) uses it to match protection to the noise level:
- 85–90 dB: SNR 20 or less
- 90–95 dB: SNR 20 to 30
- 95–100 dB: SNR 25 to 35
- 100–105 dB: SNR 30 or more
HSE says to aim for a level at the ear below 85 dB, and to avoid protectors that bring it below 70 dB. Too much protection makes it hard to talk and to hear warning signals. Its table does not suit noise with strong low frequencies, such as generators and boiler houses.
NRR and SNR come from different test methods, so a product often shows two different numbers. Compare products on the same rating.
Choosing a Rating
Measure the noise first with the decibel meter, or the workplace noise meter for a work shift, then pick a rating that brings the level at your ear under 85 dB without dropping it below 70 dB.
- Concerts and playing music: low, flat-attenuation plugs keep music clear. Compare musician's earplugs by rating and filter.
- Children: earmuffs sized for small heads, in our kids' ear defenders guide.
- Sleep: a high rating helps with snoring, but comfort matters more for side sleepers. Compare sleep earplugs by rating and type.