Noise Level and Safe Exposure Calculator
Compare dB levels of common sounds and calculate NIOSH daily exposure time at any level.
Covers workplace, concert, traffic, and power tool noise.
Sound pressure level (SPL) is measured in decibels (dB): a logarithmic unit. Because of this logarithmic scale, every 10 dB increase represents a sound that is 10 times more intense in energy, but only approximately twice as loud to human perception (following the Stevens power law).
The decibel formula:
L (dB) = 10 × log₁₀(I ÷ I₀)
Or in terms of sound pressure:
L (dB) = 20 × log₁₀(P ÷ P₀)
Variable definitions:
- L = sound level in decibels (dB)
- I = sound intensity (W/m²)
- I₀ = reference intensity = 10⁻¹² W/m² (threshold of hearing)
- P = sound pressure (Pa)
- P₀ = reference pressure = 20 μPa (threshold of hearing)
Adding sound sources:
L_combined = 10 × log₁₀(10^(L1/10) + 10^(L2/10))
Two identical sound sources together are only 3 dB louder than one — not double.
Reference sound levels:
| Source | Approximate dB |
|---|---|
| Threshold of hearing | 0 dB |
| Whisper | 30 dB |
| Quiet library | 40 dB |
| Normal conversation | 60 dB |
| Busy restaurant | 75 dB |
| Lawnmower | 90 dB |
| Rock concert | 110 dB |
| Jet engine at 100 ft | 140 dB |
| Pain threshold | 130–140 dB |
Safe exposure limits (OSHA, US):
| SPL | Maximum Daily Exposure |
|---|---|
| 85 dB | 8 hours |
| 90 dB | 4 hours |
| 95 dB | 2 hours |
| 100 dB | 1 hour |
| 105 dB | 30 minutes |
| 115 dB | 15 minutes |
Noise-induced hearing loss is permanent and cumulative. Wear hearing protection at any sustained exposure above 85 dB.