Tech Tools / SPL Drop-off
SPL Drop-off
Enter source SPL at a reference distance. See level at each seat row with inverse-square (−6 dB per doubling) or near-field line-array (−3 dB per doubling).
Use at your own risk. Real rooms have reflections, air absorption, and array geometry that change measured SPL. Inverse-square is a free-field point-source model. Line-array −3 dB/doubling applies only in the near/cylindrical zone and is a simplification. This tool is a planning aid only. Always verify against manufacturer documentation and on-site measurements before deploying to a show.
| Label | Distance | SPL | Δ from ref |
|---|
Sources
- Inverse-square law: SPL₂ = SPL₁ − 20·log₁₀(d₂/d₁) → −6.02 dB per distance doubling (point source, free field).
- Cylindrical/line near-field approximation: −10·log₁₀(d₂/d₁) → −3.01 dB per doubling (simplified line-array near zone).
- Air absorption: ISO 9613-1 qualitative note only in this tool.
Tuning coverage?
Kynetic designs PA systems for corporate and medical shows.