Sound Level and Distance Calculator
Sound level at a new distance, the intensity and pressure behind it, and the level from several identical sources.
Results
Sound level
65.000
dB
Sound intensity
0.000316228
W/m²
Sound pressure
0.35566
Pa
Sound level
85.000
dB
What this tool does
Sound from a point source spreads over a sphere, so the level drops six decibels every time the distance doubles — the inverse square law written in decibels. This assumes open air with nothing to reflect off; indoors, walls bounce sound back and the drop is much smaller.
Formula
L = 10 log₁₀(I ÷ I₀) (I₀ = 10⁻¹² W/m²)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
db | Sound level | dB |
d1 | Distance | m |
d2 | Distance | m |
ns | Identical sources | — |
L2 | Sound level | dB |
IN | Sound intensity | W/m² |
PR | Sound pressure | Pa |
LN | Sound level | dB |
Worked example
- Sound level85 dB
- Distance1 m
- Distance10 m
- Identical sources1
- Sound level65.000 dB
- Sound intensity0.000316228 W/m²
- Sound pressure0.35566 Pa
- Sound level85.000 dB
Limitations
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.
- This tool is informational only. It does not diagnose, treat or replace a qualified health professional. Speak to a doctor before making decisions about your health.
Frequently asked questions
Why do two identical machines not make twice the decibels?
Because decibels are logarithmic, not additive. Doubling the sound energy adds three decibels, not doubles the number: two 80 dB machines make 83 dB, and it takes ten of them to reach 90. The same scale explains why moving twice as far away only takes six decibels off.