Formula and example
How it is calculated
L₂ = L₁ − 20 × log₁₀(r₂/r₁)
Worked example
In a free sound field, 80 dB at 1 m becomes approximately 73.98 dB at 2 m.
Things to check
- The geometric spreading of sound energy produces a decrease of approximately 6 dB each time the distance doubles.
- Walls, the ground, other sources and air absorption can substantially change the real situation.