Hearing Protection Calculator
Effective ear noise from NRR with derating, plus protection verdict.
What it does
Package ratings come from laboratories while ears live on job sites, so regulators discount the label before trusting it. Foam plugs keep half their NRR, earmuffs keep three quarters, and other plugs keep three tenths; subtract 7 dB more for A-weighted math. The tool above lands the estimated ear level with a verdict.
The default pairs 95 dBA with NRR 30 foam plugs. Derating halves 30 to 15, minus 7 leaves 8 dB of credit, and 95 minus 8 is 87 dBA, still above the 85 line. Stronger plugs, muffs, or quieter tasks close the last 2 dB.
Two federal sources frame the method. A NIOSH criteria document sets the variable scheme of 25, 50, and 70% off by protector type with the minus 7 step for A-weighted levels, while the OSHA standard appendix runs the same NRR minus 7 procedure for checking adequacy. Both warn that fit decides whether estimates hold.
Estimates never replace fit and wear time. A plug in a pocket protects nothing, and even perfect math fails with poor insertion, which is why modern programs verify with fit testing. Treat the verdict as a shopping filter, then train, fit, and recheck.
How to use
- Type the workplace noise in dBA.
- Type the package NRR in dB.
- Pick earmuffs, foam plugs, or other plugs.
- Read the ear level first.
- Read the verdict against the 85 dBA line.
Formula
- NRR (dB)
- Laboratory label rating.
- kept
- Derated credit by protector type.
- 7 dB
- A-weighting adjustment in the method.
NIOSH variable derating with the A-weighted minus 7 step. C-weighted sound needs no 7 dB step under the same appendix.
Worked example
Example: 95 dBA, NRR 30 foam
Defaults: noise 95, NRR 30, foam plugs.
- Derate: 30 x 0.50 = 15 dB kept.
- Adjust: 15 minus 7 = 8 dB credit.
- Ear: 95 minus 8 = 87 dBA.
- Line: 87 sits above 85, so Still over 85.
- Tool shows 87 dBA, Still over 85, 15 dB used.
Reference table
| Protector | Kept | Ear |
|---|---|---|
| Earmuffs | 22.5 dB | 84.5 dBA |
| Foam plugs | 15 dB | 92 dBA |
| Other plugs | 9 dB | 98 dBA |
Limits
- Estimates only; fit testing measures reality.
- Assumes full shift wear without breaks.
- Impulse noise needs separate treatment.
- 85 line is occupational, not concert, guidance.
Common mistakes
- Trusting the full label NRR as worn.
- Skipping the minus 7 on A-weighted math.
- Mixing protector types in one estimate.
- Wearing plugs half inserted.
- Ignoring the verdict above 85.
Try it yourself
Quick checks. Answers sit tucked under each question.
90 dBA, NRR 25 muffs?
Keep 18.75, ear 90 minus 11.75 = 78.3 dBA, Protected.
100 dBA, NRR 33 other plugs?
Keep 9.9, ear 100 minus 2.9 = 97.1 dBA, Still over 85.
Which type protects most here?
Earmuffs keep the largest share of their label.
Questions
What is NRR?
The laboratory label rating in dB on each package.
Why derate?
Field fit trails lab fit, so regulators discount the label.
Foam plugs at 95 dBA?
NRR 30 leaves about 87 dBA, still over the line.
What is the 85 line?
The occupational exposure marker used in verdicts here.
Does fit matter?
Enormously. Poor insertion erases the whole estimate.
Muffs or plugs?
Muffs keep 75% of label; foam keeps 50%.