NRR Calculator — Hearing Protector Noise Reduction
Find the real-world noise reduction from your earplugs or earmuffs: enter the ambient sound level and the NRR on the package, and see the protected exposure versus NIOSH and OSHA safety limits.
dBA
dB
Protector type
Метод вычисления
Below 85 dBA NIOSH REL — hearing is protected
- 1
Labeled NRR
33 - 2
NIOSH derating (75%)
33 × 0.75 = 24,8NIOSH applies 75% of labeled NRR for earmuffs. - 3
Protected noise level
95 − 24,8 = 70,3
Как работает этот калькулятор?
The labeled NRR overstates real-world protection. NIOSH recommends using 75% of NRR for earmuffs and 50% for foam plugs; the EPA/OSHA formula uses (NRR−7)/2. Subtract the result from ambient dBA to get your protected exposure. Target below 85 dBA for safe 8-hour hearing protection.
Формула
How this is calculated
A hearing protector's Noise Reduction Rating (NRR) is measured under ideal laboratory conditions where trained subjects insert or position the protector perfectly. Real-world protection is always lower because of imperfect fit, hair, glasses, or simply not wearing the device correctly. Two derating approaches exist to translate the label NRR into a realistic estimate.
NIOSH (National Institute for Occupational Safety and Health) published type-specific derating factors in 1998: use 75% of the labeled NRR for earmuffs and 50% for formable foam earplugs. These values were derived from field measurements and represent median real-world attenuation. Subtract the derated figure from the ambient A-weighted sound level to get the estimated protected exposure. The EPA / OSHA formula applies a blanket 50% derating after subtracting 7 dB to account for the difference between C-weighted laboratory measurements and A-weighted worksite readings: effective = (NRR − 7) / 2.
NIOSH recommends targeting a protected level at or below 85 dBA as an 8-hour time-weighted average — its Recommended Exposure Limit (REL). OSHA's Permissible Exposure Limit (PEL) is 90 dBA. If either limit is exceeded, choose a higher-rated protector, use dual protection (earmuff over earplug), or reduce time at that noise level. Actual protection varies with fit, noise spectrum, and duration; these formulas are estimates for engineering control planning, not guarantees.
Часто задаваемые вопросы
The NRR is measured in a laboratory with trained subjects who achieve an optimal fit. In workplaces, plugs are often inserted too shallowly and earmuffs may not seal fully around glasses or hair. NIOSH derating (50–75%) accounts for this gap between ideal and typical performance.
NIOSH recommends 85 dBA as the maximum 8-hour time-weighted average to prevent noise-induced hearing loss. OSHA's legal Permissible Exposure Limit is 90 dBA. Prolonged exposure above 85 dBA causes irreversible damage — the risk doubles with every 3 dB increase above the threshold.
Yes — dual protection is used in very high-noise environments (above 105 dBA). The combined NRR is not simply additive; the practical combined effective reduction is roughly the higher NRR plus 5 dB, then derated normally. Even so, any protected level above 85 dBA still requires hearing conservation measures.
Также известен как
TG we-Calculate Editorial Team. (2026). NRR Calculator — Hearing Protector Noise Reduction [Online calculator]. TG we-Calculate. https://we-calculate.com/ru/calculator/nrr-calculator
TG we-Calculate Editorial Team. "NRR Calculator — Hearing Protector Noise Reduction." TG we-Calculate. 2026. https://we-calculate.com/ru/calculator/nrr-calculator.
TG we-Calculate Editorial Team, "NRR Calculator — Hearing Protector Noise Reduction," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/ru/calculator/nrr-calculator
@misc{wecalculate_nrr_calculator, title = {NRR Calculator — Hearing Protector Noise Reduction}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/ru/calculator/nrr-calculator}}, year = {2026}, note = {TG we-Calculate} }
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