ToolsSound, propagation & hearing
Sound pressure, intensity & SPL
Convert between dB SPL, pascal, sound intensity, particle velocity and their levels.
dB SPL
Pa
mPa
W/m²
dB
mm/s
dB
°C
Characteristic impedance of air: 413.3 Pa·s/m
| 0 dB | 2e-5 Pa | Threshold of hearing at 1 kHz |
| 20 dB | 0.0002 Pa | Recording studio, very quiet |
| 30 dB | 0.000632 Pa | Quiet bedroom at night |
| 40 dB | 0.002 Pa | Quiet library |
| 60 dB | 0.02 Pa | Normal conversation at 1 m |
| 70 dB | 0.0632 Pa | Busy office, vacuum cleaner |
| 85 dB | 0.356 Pa | Heavy traffic at the kerb; hearing-protection action level |
| 94 dB | 1 Pa | Calibrator reference (1 Pa) |
| 100 dB | 2 Pa | Loud nightclub |
| 110 dB | 6.32 Pa | Rock concert near the stage |
| 120 dB | 20 Pa | Threshold of discomfort |
| 130 dB | 63.2 Pa | Threshold of pain |
How it works
Sound pressure is what microphones and ears respond to. In a plane wave, intensity (power per area) and particle velocity follow from the pressure and the characteristic impedance of air.
Because the reference values were chosen to match, sound pressure level and sound intensity level are almost the same number in a free field.
Formulas
- p = 20 µPa · 10^(L / 20)
- I = p² / Z₀
- v = p / Z₀
- Z₀ = ρ · c ≈ 413 Pa·s/m at 20 °C
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