SPL Calculator & Distance Attenuation
Convert Pascals to dB SPL and calculate noise attenuation over distance. Includes OSHA/NIOSH safety zones.
Converter: Pa ↔ dB
Distance Attenuation
About
Acoustic monitoring is a health mandate in industrial and event environments. The human ear perceives sound logarithmically, meaning linear changes in pressure (Pascals) translate to complex changes in perception (Decibels). Engineers must accurately convert these values to assess compliance with noise control regulations.
This tool performs the conversion from Sound Pressure (p) to Sound Pressure Level (Lp) relative to the human hearing threshold. It also applies the Inverse Square Law to predict how noise levels drop as distance increases, a critical calculation for zoning safety perimeters around generators, PA systems, or heavy machinery.
Formulas
SPL from Pressure:
Lp = 20 ⋅ log10pp0
Where p0 = 20µPa (Reference)
Distance Attenuation (Inverse Square Law):
L2 = L1 − 20 ⋅ log10r2r1
Reference Data
| Source Environment | Pressure (Pa) | Level (dB SPL) | Max Safe Exposure (NIOSH) |
|---|---|---|---|
| Jet Engine (30m) | 200 | 140 | Immediate Damage |
| Thunderclap | 20 | 120 | < 9 seconds |
| Chainsaw / Rock Concert | 2 | 110 | ~2 minutes |
| Jackhammer | 0.63 | 100 | 15 minutes |
| Subway Train | 0.2 | 90 | 2 hours |
| Heavy Traffic | 0.063 | 85 | 8 hours (Work limit) |
| Vacuum Cleaner | 0.02 | 70 | Safe Indefinitely |
| Conversation | 0.002 | 60 | Safe Indefinitely |
| Quiet Library | 0.0002 | 40 | Safe Indefinitely |
| Hearing Threshold | 0.00002 | 0 | N/A |