Noise Dose Calculation
This calculator helps determine OSHA noise dose and Time-Weighted Average (TWA) for workplace noise exposure assessment.
D = 100 × Σ(Cₙ / Tₙ)
Where:
- D = Noise dose percentage
- Cₙ = Time spent at a specific noise level
- Tₙ = Permissible time at that level (T = 8 / 2(L-90)/5)
TWA = 16.61 × log10(D/100) + 90
Where TWA is the 8-hour Time-Weighted Average sound level.
OSHA Requirements: A hearing conservation program is required for all employees exposed to TWA of 85 dB or higher.
Results
Noise Dose
TWA
Compliance Status
Action Required
Interpretation
Exposure Details
| Noise Level (dBA) | Exposure Time (hrs) | Permissible Time (hrs) | Partial Dose (%) |
|---|
Practical Examples
Example 1: Combined Exposures
A worker is exposed to 95 dBA for 3 hours and to 90 dBA for 5 hours.
D = 100 × (3/4 + 5/8) = 100 × (0.75 + 0.625) = 137.5%
This exceeds the OSHA limit of 100% dose.
Example 2: TWA Calculation
For a noise dose of 139.3%:
TWA = 16.61 × log10(139.3/100) + 90 = 92.39 dBA
This exceeds the 85 dBA action level requiring a hearing conservation program.
Example 3: Single Exposure
A worker is exposed to 100 dBA for 1 hour:
Permissible time at 100 dBA: T = 8 / 2(100-90)/5 = 8 / 22 = 2 hours
D = 100 × (1/2) = 50% (within limits)
OSHA Noise Exposure Limits
| Noise Level (dBA) | Permissible Exposure Time | Dose per Hour (%) |
|---|---|---|
| 90 | 8 hours | 12.5% |
| 92 | 6 hours | 16.7% |
| 95 | 4 hours | 25% |
| 97 | 3 hours | 33.3% |
| 100 | 2 hours | 50% |
| 105 | 1 hour | 100% |
| 110 | 30 minutes | 200% |
| 115 | 15 minutes | 400% |
Note: Continuous exposure to noise levels above 115 dBA is not permitted under any circumstances.