Noise Dose Calculator
Calculate OSHA noise dose percentage and TWA from segmented dBA exposures using the 5-dB exchange rate formula.
About this calculator
Under OSHA's 29 CFR 1910.95, a worker's noise exposure isn't judged by a single decibel reading but by an accumulated dose across the whole shift, and this calculator implements that math directly: for each of up to four exposure segments you enter, it computes the allowable hours at that sound level as Ti = 8 / 2^((Li − 90) / 5) — OSHA's 5 dB exchange rate, meaning every 5 dB increase halves the time you're allowed to be exposed — then sums each segment's actual hours divided by its allowable hours to get the total dose fraction, multiplied by 100 for a percentage. A dose of 100% corresponds exactly to the Permissible Exposure Limit (a full shift at 90 dBA); 50% is OSHA's Action Level (equivalent to 85 dBA), which is the trigger for a hearing conservation program even though it isn't itself a violation. The code also back-calculates an 8-hour Time-Weighted Average in dBA from the dose using TWA = 16.61 × log10(D/100) + 90, and projects an annualized dose-days figure by multiplying the daily dose percentage across 250 assumed workdays per year, useful for spotting cumulative risk in mixed-exposure jobs.
One important detail: segments below 80 dBA are treated as having infinite allowable time (they don't count toward dose at all) per OSHA's rules, so low-level background noise legitimately contributes zero even if you're exposed to it all day. Enter each distinct noise level and its duration honestly — dose calculations are very sensitive to the loudest segments, since the exchange rate is exponential, not linear.
Inputs
Results
Noise dose (%)
81.3%
Figures current as of 2026. Source: U.S. Department of Labor, Occupational Safety and Health Administration, 29 CFR 1910.95, Occupational Noise Exposure — Table G-16 (Permissible Noise Exposures) and 1910.95(c)(1) (85 dBA 8-hour TWA hearing conservation action level)
How to Use This Calculator
- Enter Segment 1 level (dBA), Segment 1 duration (hrs), and Segment 2 level (dBA).
- Set Segment 2 duration (hrs), Segment 3 level (dBA), and Segment 3 duration (hrs).
- Adjust Segment 4 level (dBA), Segment 4 duration (hrs) as needed.
- Review the Noise dose (%) result.
- Use 8-hr TWA (dBA) and Total exposure hours to inform your decision.
How the result changes with Segment 1 level (dBA)
| Segment 1 level (dBA) | Noise dose (%) |
|---|---|
| 48 | 31.3% |
| 71 | 31.3% |
| 143 | 38,833.6% |
| 150 | 102,431.3% |
What each input means
- Segment 1 level (dBA)
- Sound level in decibels (A-weighted) during segment 1.
- Segment 1 duration (hrs)
- Hours of exposure at segment 1 level.
- Segment 2 level (dBA)
- Sound level during segment 2.
- Segment 2 duration (hrs)
- Hours of exposure at segment 2 level.
- Segment 3 level (dBA)
- Sound level during segment 3.
- Segment 3 duration (hrs)
- Hours of exposure at segment 3 level.
- Segment 4 level (dBA)
- Sound level during segment 4 (leave 0 if unused).
- Segment 4 duration (hrs)
- Hours of exposure at segment 4 level.
What each result means
- Noise dose (%)
- Total noise dose as percentage. 100% = OSHA PEL (90 dBA TWA).
- 8-hr TWA (dBA)
- Time-Weighted Average sound level over an 8-hour shift.
- Total exposure hours
- Sum of all segment durations.
- Exceeds action level?
- 1 if dose ≥ 50% (TWA ≥ 85 dBA), 0 otherwise.
- Exceeds PEL?
- 1 if dose ≥ 100% (TWA ≥ 90 dBA), 0 otherwise.
- Annual dose-days
- Projected cumulative dose over 250 working days.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersSegment 1 level (dBA) = 95, Segment 1 duration (hrs) = 2, Segment 2 level (dBA) = 85, Segment 2 duration (hrs) = 4 = 8 input(s) provided
- Calculate Noise doseNoise dose = doseFraction * 10081.3 = 81.3
- Calculate 8-hr TWA88.5 = 88.5
- Calculate Total exposure hoursTotal exposure hours8 = 8
Figures and sources
- OSHA 29 CFR 1910.95 — permissible noise exposures (Table G-16), 5 dB exchange rate, and hearing conservation action level (2026) — U.S. Department of Labor, Occupational Safety and Health Administration, 29 CFR 1910.95, Occupational Noise Exposure — Table G-16 (Permissible Noise Exposures) and 1910.95(c)(1) (85 dBA 8-hour TWA hearing conservation action level)
Engine last updated . Checked against 4 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why does a 5 dB increase cut my allowed exposure time in half?
OSHA's exchange rate formula, Ti = 8 / 2^((Li − 90) / 5), doubles the exponent's effect for every 5 dB step, which is what makes the allowable-hours curve fall off so steeply — 90 dBA allows a full 8-hour shift, 95 dBA only 4 hours, and 100 dBA just 2 hours. It reflects the assumption that sound energy (and hearing-damage risk) roughly doubles for every 3 dB in physical terms, but OSHA specifically chose a more lenient 5 dB rate for regulatory purposes.
What's the practical difference between the Action Level and the PEL?
The 50% dose Action Level (equivalent to an 85 dBA TWA) is the trigger for OSHA's Hearing Conservation Program — audiometric testing, hearing protection availability, and training — but by itself isn't a citable violation. The 100% dose PEL (90 dBA TWA) is the actual Permissible Exposure Limit; exceeding it is a compliance violation requiring engineering or administrative controls, not just monitoring.
Why doesn't a segment below 80 dBA add anything to my dose?
The calculator's allowableHours function returns Infinity for any level under 80 dBA, meaning OSHA treats time at those levels as contributing zero dose regardless of duration. This reflects the regulation's own threshold — sound below 80 dBA isn't considered part of the noise-dose accounting at all, even if you're exposed to it for the entire shift.
How does the calculator convert my dose percentage into an 8-hour TWA in dBA?
It applies TWA = 16.61 × log10(D/100) + 90, which is the OSHA-specified inverse of the dose formula — it answers 'what single, constant 8-hour sound level would have produced this same dose?' Because the relationship is logarithmic, a dose of 200% only adds about 5 dB to the TWA (95 dBA), which is a useful sanity check when comparing dose percentages across different jobs.
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