Hearing Protection Attenuation Calculator
Estimate the noise level reaching the ear under a hearing protector using the SNR (Single Number Rating) method, then check it against the 85 dBA criterion. Enter the workplace exposure level and the protector's SNR to see the protected level, the effective attenuation applied, and whether the fit is adequate or over-protective.
Enter Values
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How to use this calculator
- Enter the measured workplace noise exposure level in A-weighted decibels (dBA).
- Enter the hearing protector's SNR (Single Number Rating) in dB from the product data sheet.
- Read the protected level at the ear, aiming for at or below 85 dBA but not below about 70 dBA (over-protection).
How it works
The SNR method gives an effective attenuation of SNR − 4 dB (the 4 dB is a standard correction), so the protected level = exposure level − (SNR − 4). A protected level at or below 85 dBA is treated as adequate for the common 85 dBA criterion; below roughly 70 dBA the protector is over-attenuating, which can cut the wearer off from alarms and speech.
Worked example
Worked example. For a 95 dBA exposure with an SNR 25 protector, the effective attenuation is 25 − 4 = 21 dB, so the protected level is 95 − 21 = 74 dBA — adequate, and close to the point where over-protection would start to be a concern.
Common mistakes
- Assuming the full laboratory SNR is achieved in practice — real attenuation is usually much lower, so many programs derate it by 25–50%.
- Ignoring wear-time: removing the protector even briefly in a loud area sharply reduces the effective daily protection.
- Over-protecting: choosing the highest-rated device available can push the level below 70 dBA and isolate the wearer from warnings.
Frequently asked questions
Why subtract 4 dB from the SNR?
The SNR method includes a fixed 4 dB correction to account for real-world variability, so the effective attenuation applied to the exposure is SNR − 4, not the raw SNR.
Is a lower protected level always better?
No. Bringing the level to around 70–80 dBA is usually ideal; below about 70 dBA the wearer can become dangerously isolated from alarms, vehicles and speech, so over-protection is its own hazard.
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Tip: Enter any known values to calculate the remaining results.
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