Distance Attenuation Calculator

Your details

A point source radiates equally in all directions (-6 dB per doubling of distance). A line source spreads cylindrically (-3 dB per doubling). A plane source has no geometric spreading loss.
Sound pressure level measured or specified at the reference distance (dB re 20 µPa).
dB
The distance at which the reference SPL was measured.
m
The distance at which you want to know the sound level.
m
Adds air absorption loss (approx. 0.0048 dB/m at 1 kHz, 20 C, 50% RH per ISO 9613-1). Significant over long outdoor distances.
SPL at target distanceLoud
70dB

Sound pressure level at the target distance

Geometric spreading loss20dB
Atmospheric absorption loss0dB
Total attenuation20dB
Drop per doubling of distance6dB
70 dB
Near silence<30Quiet30-55Moderate55-70Loud70-85Very loud85-100Hazardous100+

SPL at target is 70.0 dB.

  • Sound drops by 20.0 dB between 1 m and 10 m from the source.
  • That is 3.3 doublings of distance, each costing roughly 6 dB for a point source.
  • Sustained exposure above 70 dB can cause fatigue and long-term hearing risk for sensitive individuals.

Next stepTo reduce noise at the target distance, halving distance to the source gains 6 dB (point source), or add barrier and enclosure treatments.

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