Decibel Distance Calculator
Enter a known sound level and distance, then find the SPL at any new distance using the inverse-square law.
Sound Source Parameters
Common Reference Levels
Threshold of hearing0 dB
Whisper (1 m)30 dB
Normal conversation (1 m)60 dB
Lawnmower (1 m)90 dB
Rock concert (1 m)110 dB
Jet engine (1 m)140 dB
Enter values and press Calculate to see the result.
SPL at New Distance
—
decibels (dB SPL)
dB Change
—
from reference
Distance Ratio
—
d2 / d1
SPL at Doubling Distances
Formula: SPL2 = SPL1 − 20 × log10(d2 / d1) — Inverse-square law for a point source in a free field.
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Summary
Enter a known sound level and distance, then find the SPL at any new distance using the inverse-square law.
How it works
- Enter the known sound level in decibels (dB) at a reference distance.
- Enter the reference distance where that level was measured.
- Enter the new distance at which you want the SPL.
- Select your preferred distance unit (meters or feet).
- The calculator applies the formula: SPL2 = SPL1 − 20 × log10(d2 / d1).
- Results show the new SPL and the dB change between the two distances.
Use cases
- Estimate noise levels from construction sites at surrounding properties.
- Plan speaker placement in a concert venue or home theater.
- Calculate safe listening distances from industrial machinery.
- Verify OSHA or occupational noise exposure compliance at workplaces.
- Design outdoor event sound systems with predictable coverage.
- Assess aircraft or traffic noise at various distances from a source.
- Educate students on acoustics and the inverse-square law.
Frequently Asked Questions
Last updated: 2026-06-09 ·
Reviewed by Nham Vu