Noise Exposure (TWA / Dose) Calculator

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.

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.

0.0%

Total Noise Dose

Equivalent 8-Hr TWA (dBA)

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.