Point-source far-field geometrical spreading per distance doubling; setback economics depend on land and receptor geometry
~6 dBderived
| Value kind | derived — Derived values are guide calculations; their result is only as fixed as the stated inputs, scope, and method. |
|---|---|
| Scope | About 6 dB per distance doubling for unchanged far-field point-source directivity and propagation terms. Setback adds no attenuation hardware or its maintenance, but consumes land; compare its land and layout cost with source treatment. An extended line-source regime approaches 3 dB per doubling. |
| As of | 2017 |
| Source | ASHRAE Handbook, Sound and Vibration, logarithmic distance attenuation. · Sound propagation; point-source geometrical spreading |
| Derivation | For unchanged far-field point-source geometry, 20 log10(2) = 6.0206 dB, rounded to approximately 6 dB per doubling; an extended line has a different spreading law. |
| Review | checking…review by 2027-09-08 · standard cadence |
| Recorded changes | last 2026-09-16 · 2 revisions tracked |
| Claim id | attenuation-per-doubling-of-distance-from-a |
Where the guide uses it
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