Noise Exposure (TWA / Dose) Calculator
Formula Reference
Permitted Duration at level L: T = 8 ÷ 2^((L − Criterion) ÷ Exchange) hours (segments below the threshold level are excluded)Dose: Dose (%) = 100 × Σ (Actual Duration ÷ Permitted Duration) for every included segment
Equivalent TWA: TWA = Criterion + Exchange × log₂(Dose ÷ 100)
| OSHA Hearing Conservation | 90 dBA / 5 dB / 80 dBA threshold |
| OSHA PEL Compliance | 90 dBA / 5 dB / 90 dBA threshold |
| NIOSH REL | 85 dBA / 3 dB / 80 dBA threshold |
Key Thresholds
Under OSHA (29 CFR 1910.95), a dose of 50% (85 dBA TWA) triggers mandatory enrollment in a Hearing Conservation Program (audiometric testing, training, hearing protection availability). A dose of 100% (90 dBA TWA) is the Permissible Exposure Limit (PEL) — exceeding it requires feasible engineering or administrative controls. NIOSH's Recommended Exposure Limit (REL) is more protective, treating 85 dBA as its own 100% dose reference point.Methodology, interpretation & sources
Purpose. Calculate an employee's noise dose (%) and equivalent 8-hour Time-Weighted Average (TWA) exposure from multiple sound-level/duration segments in a shift, using OSHA or NIOSH methodology.
How to use the result. Start with source data you can verify, enter values on a consistent unit and time basis, and record the assumptions used. The main inputs on this page include Reporting Standard Sets the criterion level, exchange rate, and integration threshold used in the calculation., Criterion (dBA), Exchange Rate (dB), Threshold (dBA), Noise Exposure Segments Add one row per distinct sound level the worker was exposed to, with its duration. Rows below the threshold level are automatically excluded from the dose., Your Name. Re-run the calculation when those assumptions change rather than carrying an old result forward.
Decision use. Use this result as a screening or planning aid for occupational hygiene work. Exposure decisions should be based on competent sampling, calibrated instruments, current limits and task-specific assessment.
Limitations. Short-term peaks, mixtures, PPE, work/rest cycles, environmental conditions and jurisdiction-specific limits may not be fully represented by a simplified calculator.
Primary references. Use the current edition/version that applies to your jurisdiction and organization:
Editorial note. Prepared and maintained by Impact Tech Solutions. Editorially updated 28 September 2026. No individual professional credential is claimed on this page; high-consequence, statutory, tax, engineering or health decisions should be independently verified against the current primary source and, where required, a qualified professional.