Distance Attenuation Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

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The value of a distance attenuation calculator is speed without losing the physics behind the answer. Wave and sound calculations are sensitive to the chosen medium and to whether the page is working with amplitudes, powers, or ratios. Keep that relationship in view as you replace the defaults with your own data.

What this calculator does

The Distance Attenuation Calculator is a focused solver for sound pressure level — point 2 using Distance from the source — Point 1, Sound pressure level — Point 1, Distance from the source — Point 2. Its job is to make the active equation and the quantities feeding it easy to inspect rather than model every possible real-world effect.

How to use it

Begin with Distance from the source — Point 1, Sound pressure level — Point 1, Distance from the source — Point 2. Do not strip the units from those values when copying them from a datasheet or measurement. Once calculated, vary the most influential input slightly and confirm that the response agrees with the equation before using the number elsewhere.

How the calculation works

The free-field point-source model uses L₂ = L₁ − 20log₁₀(r₂/r₁). Doubling distance therefore reduces sound-pressure level by about 6 dB in this ideal spreading model.

Example

Using the default example on the page (Distance from the source — Point 1 = 1 m; Sound pressure level — Point 1 = 90 dB; Distance from the source — Point 2 = 2 m), the calculator returns sound pressure level — point 2 of 83.9794 dB. This baseline lets you confirm the calculation path before entering a different geometry, material, speed, or operating condition.

How to interpret the result

For this acoustic result, first identify whether the headline is a linear quantity or a logarithmic level. Keep the medium and units fixed when comparing scenarios, and use the equation’s expected direction of change as a quick plausibility check.

Limitations and notes

The 20log distance law assumes free-field spherical spreading from a point-like source. Reflections, ground effects, barriers, absorption, source directivity, and near-field behavior can make measured attenuation very different.