SPL Over Distance
See how sound pressure level falls as you move away from a source.
About SPL Over Distance
Doubling the distance from a point source drops the level by roughly six decibels, following the inverse square law. Placing speakers or microphones correctly is a level decision, and distance attenuation explains why far listeners hear so much less.
Formula
SPL Over Distance
Attenuation = 20 x log10(new distance / reference distance)
- reference
- The distance at which the original SPL was measured
Worked example
With the default values below, SPL Over Distance returns SPL at New Distance of 80.5. Change any input above and every figure here is recalculated in your browser.
Inputs used
- SPL at referenceaccepts 0–150 dB
- 90 dB
- Reference distanceminimum 0.01 m
- 1 m
- New distanceminimum 0.01 m
- 3 m
Results
- SPL at New Distance
- 80.5 dB
- Attenuation
- 9.5 dB
- Distance Ratio
- 3.00
Step by step
- 1Values used
- 2SPL Over Distance
- 3SPL at New Distance= 80.5 dB
- 4Attenuation= 9.5 dB
- 5Distance Ratio= 3.00
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is SPL Over Distance calculated?
Attenuation = 20 x log10(new distance / reference distance) Doubling the distance from a point source drops the level by roughly six decibels, following the inverse square law.
Why does SPL Over Distance matter?
Placing speakers or microphones correctly is a level decision, and distance attenuation explains why far listeners hear so much less.
What values do I need to enter?
This calculator takes 3 inputs: SPL at reference, Reference distance, New distance. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.