Hearing protection NRR calculator
Enter the noise exposure and the NRR printed on the label. The calculator applies WorkSafeBC's derating method to estimate the level reaching the worker's ear, and tells you whether that protects enough without cutting the worker off.
Estimated level at the ear
Example from the guideEnter the exposure and the NRR to see the estimate.
80.3dBA
Acceptable
At or under 85 dBA at the ear. The best range is 75 to 80 dBA.
Optimal is 75 to 80 dBA. Under 70 is overprotection. Over 85 is insufficient.
The working
- Take the higher NRR and add 5
- 33 + 5 = 38
- Credit 65% of it
- 38 × 0.65 = 24.7
- Take off 3 dB to express it in dBA
- 24.7 − 3 = 21.7 dB
- Subtract the protection from the exposure
- 102 − 21.7 = 80.3 dBA
At 102 dBA Lex, the recommended protector class is A or AL.
Averages, not individuals. These factors estimate average protection for a group of workers. They can't show what one worker's earplugs or earmuffs deliver. That takes field-attenuation testing, often called fit testing.
Method from WorkSafeBC, Sound Advice: A Guide to Hearing Conservation Programs.
How the estimate works
The NRR on a label comes from laboratory testing, and workers on the job rarely get that much protection. WorkSafeBC's guidance credits earplugs with 50% of their NRR and earmuffs with 70%, then takes 3 dB off so the result is in dBA. The protection that remains is subtracted from the worker's noise exposure, Lex.
When both devices are worn, the guide takes the higher of the two NRRs, adds 5 for the second device, and credits 65% of the total.
| Worn | Estimated level at the ear |
|---|---|
| Earplugs | Lex − [NRR × 0.5 − 3] |
| Earmuffs | Lex − [NRR × 0.7 − 3] |
| Both | Lex − [(higher NRR + 5) × 0.65 − 3] |
Worked example
The guide's example is a faller exposed to 102 dBA Lex, with earmuffs rated NRR 26 and earplugs rated NRR 33. The calculator opens on these values, so you can check it against the guide.
| Worn | Calculation | At the ear |
|---|---|---|
| Earplugs only | 102 − [33 × 0.5 − 3] | 88.5 dBA Insufficient |
| Earmuffs only | 102 − [26 × 0.7 − 3] | 86.8 dBA Insufficient |
| Both | 102 − [(33 + 5) × 0.65 − 3] | 80.3 dBA Acceptable |
Neither device on its own brings the level under 85 dBA. Worn together, they do.
Reading the result
| Level at the ear | Outcome | What it means |
|---|---|---|
| Over 85 dBA | Insufficient | Not enough protection. |
| 80 to 85 dBA | Acceptable | Under the 85 dBA limit. |
| 75 to 80 dBA | Optimal | Protected, and still able to hear speech and warning sounds. |
| 70 to 75 dBA | Acceptable | Under the limit, close to cutting the worker off. |
| Under 70 dBA | Overprotection | Too much attenuation. |
Where a result lands exactly on 80, 75 or 70, the calculator rates it Acceptable.
Overprotection matters because the goal is a level under 85 dBA but not under 70. Too much attenuation leaves workers feeling isolated, and it can change how they hear speech, machinery and warning signals. That affects both productivity and safety.
Which class of protector?
| Exposure, Lex | Recommended class |
|---|---|
| Under 90 dBA | C |
| 90 to 95 dBA | B or BL |
| Over 95 to 105 dBA | A or AL |
| Over 105 dBA | Dual protection: at least a Class B earmuff and a Class A earplug |
Class A protection is not recommended below 95 dBA. Hearing-impaired workers in particular tend to resist it, because it stops them hearing warning signals or speech. For them, Class B or specialized protectors are more likely to be worn consistently.
What the estimate can't tell you
The derating factors estimate average protection for a group of workers. They cannot determine protection for an individual. How an earplug is inserted, or whether an earmuff seals over safety glasses, changes what one person actually gets. WorkSafeBC's guide says individual protection can only be estimated with a field-attenuation estimation system, often called fit testing.
A yearly hearing test is how you find out over time whether protection is working for each worker.
The factors, bands and class guidance on this page come from WorkSafeBC, Sound Advice: A Guide to Hearing Conservation Programs.
Short answers
What is the NRR?
The noise reduction rating is a single number on a hearing protector's label that expresses how much it reduces noise in laboratory testing.
Why isn't the NRR on the label the protection a worker actually gets?
Laboratory results overstate what workers achieve in real conditions, so WorkSafeBC's Sound Advice guide derates them: 50% of the NRR for earplugs, 70% for earmuffs, and 65% of the higher NRR plus 5 when both are worn. Then 3 dB is taken off to express the result in dBA.
What is overprotection?
Protection that brings the level at the ear below 70 dBA. The worker can feel isolated and miss speech, machinery sounds or warning signals, which affects safety and productivity.
How do I find my Lex?
Lex is the average noise level over a shift. A noise survey or personal dosimetry measures it. We offer noise surveys, and our guide on what 85 dBA means explains the limit.
Can I use the result for one worker?
No. The derating factors estimate average protection for a group of workers. How an earplug is inserted or an earmuff seals changes what one person gets, and individual protection can only be estimated with field-attenuation testing, often called fit testing.
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