Noise Exposure Calculator

The TWA and noise dose outputs describe the ambient noise environment itself -- noise level and exposure duration -- independent of what hearing protection a worker wears. Hearing protection instead affects the separate "protected noise level" and "protected dose" figures, which apply OSHA's derating formula to your entered NRR to estimate the noise level actually reaching the ear.

Under OSHA's 5 dB exchange rate, every 5 dB increase in noise level cuts the allowable exposure time in half -- the formula divides 8 hours by 2 raised to the power of (noise level minus 90) over 5. That's why relatively small increases in measured noise level can produce large swings in how long exposure is considered permissible.

OSHA's own Appendix B attenuation methods (29 CFR 1910.95) subtract 7 dB from a protector's laboratory Noise Reduction Rating -- correcting from C-weighted to A-weighted measurement -- before applying it to a TWA. This calculator adds a further 50% reduction on top of that OSHA correction, a commonly used, more conservative real-world adjustment that goes beyond what OSHA's formula alone calls for, because lab conditions consistently overstate the attenuation workers actually get from real-world fit and wear.

Yes -- across this calculator's full 0.25 to 16 hour exposure duration range, more hours of exposure at a fixed noise level always produces a higher (or equal) noise dose percentage, since dose is exposure hours divided by the allowable time at that noise level, and the allowable time itself doesn't depend on how many hours you actually enter.