Noise Exposure Calculator
Enter a sound level in A-weighted decibels (dBA) and optional exposure time. Get the maximum recommended duration and daily noise dose using NIOSH or OSHA exchange-rate formulas — the same math used in occupational hearing conservation.
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Result
The formula
Both standards limit how long you can stay at a given noise level before reaching a 100% daily dose. Allowable time halves every time the level rises by the exchange rate (3 dB for NIOSH, 5 dB for OSHA). Dose is exposure time divided by that allowable time, as a percent.
Worked example
- Concert at 100 dBA for 2 hours, NIOSH (L_c = 85, ER = 3)
- T = 8 / 2^((100−85)/3) = 8 / 2⁵ = 0.25 h = 15 min
- Dose D = 100 × (2 / 0.25) = 800% · TWA ≈ 94.0 dBA
Result: Allowable ≈ 15 min · dose ≈ 800% (far over the REL)
How noise dose is calculated
Occupational noise limits trade level for time. Louder sound is allowed for less of the day; quieter sound for longer — until the daily dose hits 100%.
NIOSH recommended exposure limit (REL)
NIOSH recommends 85 dBA as an 8-hour time-weighted average with a 3 dB exchange rate (equal-energy rule). Every +3 dB halves allowable time: 85 dBA → 8 h, 88 → 4 h, 91 → 2 h, 94 → 1 h, 100 → 15 min.
The REL is science-based guidance to limit noise-induced hearing loss over a working lifetime. It is not itself an enforceable OSHA regulation.
OSHA permissible exposure limit (PEL)
OSHA’s enforceable PEL is 90 dBA as an 8-hour TWA with a 5 dB exchange rate (29 CFR 1910.95). Allowable times are longer than NIOSH at the same level: 90 dBA → 8 h, 95 → 4 h, 100 → 2 h, 105 → 1 h.
OSHA’s action level is 85 dBA TWA (50% dose under the OSHA formula), which triggers a hearing conservation program. Engineering or administrative controls are required when the PEL is exceeded.
Dose and 8-hour TWA
For a single constant level, dose D = 100 × (C / T), where C is your exposure duration and T is the reference duration for that level. Multiple levels add as Σ(Cᵢ/Tᵢ) × 100 — this tool models one continuous level.
TWA converts dose back to an equivalent constant 8-hour level. NIOSH uses TWA = 10 log₁₀(D/100) + 85; OSHA uses TWA = 16.61 log₁₀(D/100) + 90.
Concerts, headphones, and tools
Typical A-weighted levels (approximate): busy traffic ~70–85 dBA, power lawn mower ~90–95, loud headphones or clubs ~94–105, rock concert ~100–110, chainsaw ~110–115. Peak/impulse sounds and bass-heavy venues can be higher than a phone app shows.
These limits assume the rest of the 24-hour day (and weekends) are relatively quiet. Stacking a loud shift, a concert, and loud headphones the same day understates total risk if you only check one exposure.
What this does not model
No frequency weighting beyond assuming dBA input, no impulse/peak (both NIOSH and OSHA also cite a 140 dB peak guideline), no hearing-protector attenuation (NRR), and no ototoxic chemical interactions. Consumer phone meters are approximate — use a calibrated meter or dosimeter for compliance.
Interesting facts
3 dB vs 5 dB changes everything
At 100 dBA, NIOSH allows about 15 minutes; OSHA’s 5 dB rule allows about 2 hours. Same sound, very different “100% dose” clocks — which is why NIOSH is often preferred for personal risk decisions.
Hearing loss is permanent but preventable
NIOSH estimates tens of millions of U.S. workers face hazardous noise each year. Noise-induced hearing loss and tinnitus do not heal — distance, quieter settings, and well-fitted protection do.
85 dBA is the usual hazard cue
If you must raise your voice to talk to someone an arm’s length away, levels are often near or above ~85 dBA — a practical field check when you lack a meter.
Action level ≠ PEL
Under OSHA, 85 dBA TWA (50% dose) starts hearing-conservation duties; 90 dBA TWA (100% dose) is the PEL. Many people confuse the two thresholds.
Equal energy is the science default
A 3 dB exchange rate matches the physical doubling of sound energy. International occupational guidance increasingly follows that model; OSHA’s 5 dB rate remains a U.S. regulatory compromise.
Frequently asked questions
Measure or estimate the level in dBA, choose NIOSH for a protective personal limit, and read the allowable time. At ~100 dBA NIOSH allows about 15 minutes at 100% dose — so a two-hour show is many times over unless you use hearing protection.
NIOSH recommends 85 dBA / 8 h with a 3 dB exchange rate. OSHA enforces 90 dBA / 8 h with a 5 dB exchange rate and uses 85 dBA TWA as an action level. NIOSH is stricter for the same loud level.
100% means you used the full daily allowance for that standard. 50% under OSHA is the action level. Values above 100% mean you exceeded the criterion for that day under the chosen formula.
Roughly: 85 is heavy traffic or a loud blender; ~94 is a motorcycle or mower; ~100 is a loud club, concert, or headphones turned up. Every few dB matters because of the exchange rate.
Proper protectors reduce the level at the ear. This tool does not apply NRR derating — enter the estimated protected level, or stay well under the unprotected allowable time.
Many apps are rough ± several dB. Good enough to see you are in a hazardous range; not enough for OSHA compliance. Calibrated meters and dosimeters are the workplace standard.
Many jurisdictions use a 3 dB exchange rate similar to NIOSH, with different action and limit values (for example EU Directive 2003/10/EC). This page focuses on NIOSH and OSHA formulas.
References
- Criteria for a Recommended Standard: Occupational Noise Exposure (Publication 98-126) Defines the 85 dBA REL, 3 dB exchange rate, dose, and TWA formulas.
- About occupational hearing loss Public-facing summary of hazardous noise, REL context, and prevention.
- 29 CFR 1910.95 — Occupational noise exposure Enforceable PEL, action level, and hearing conservation requirements.
- 1910.95 App A — Noise exposure computation Mandatory dose formula, Table G-16a reference durations, and OSHA TWA conversion.