Sound Distance Attenuation Calculator
Calculate how much sound level drops in decibels as distance from the source increases, free and instant online.
Enter Values
How to use this calculator
- Enter the known sound level (dB) and the distance it was measured at.
- Enter the new distance you want the level for.
- Read the predicted level and the change in dB.
How it works
The Sound Distance Attenuation Calculator estimates how a sound level changes with distance for a point source in the open (free field), using the inverse-square law.
Level at the new distance = original level − 20·log₁₀(new distance ÷ reference distance). That works out to a 6 dB drop each time the distance doubles. Rooms, reflections and barriers change the real result.
Worked example
100 dB at 1 m. At 4 m the level is 100 − 20·log₁₀(4) ≈ 88 dB — a 12 dB drop (two doublings of distance).
Frequently asked questions
Why 6 dB per doubling and not more?
Sound intensity follows the inverse-square law, but the decibel scale is logarithmic. Doubling distance quarters the intensity, which is −6 dB on the dB (sound pressure level) scale.
Does this work indoors?
It's a free-field estimate for a point source outdoors. Inside, reflections build up a reverberant field, so the level falls off more slowly than the inverse-square law predicts.
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Cite this tool
Zerdly. (2026). Sound Distance Attenuation Calculator. Retrieved from https://www.zerdly.com/tools/sound-distance-attenuation-calculator/
Tip: Enter any known values to calculate the remaining results.
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