Sound level vs distance calculator
Enter a measured level, its distance and a new distance to get the expected level there. Useful for estimating generator or AC unit noise further away.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter measured level, measurement distance and new distance.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
L₂ = L₁ − 20 × log₁₀(r₂ / r₁), about 6 dB less for every doubling of distance.
Example
Inputs: Measured level = 100 dB, Measurement distance = 1 m, New distance = 10 m. Result: Level at new distance: 80 dB; Change in level: -20 dB.
Limits and caveats
- It assumes a point source in a free field with no reflecting walls. Indoors the drop is smaller because of reflections.
- Air absorption and barriers are not included; both add extra loss over long distances.
Questions about this tool
Why 6 dB less for each doubling of distance?
The energy spreads over a sphere whose area grows with distance squared, so intensity falls to a quarter.
Does it apply to a busy road?
A continuous road behaves like a line source and drops only about 3 dB per doubling of distance.
Can I calculate moving closer?
Yes. Enter a smaller new distance and the level comes out higher than measured.