Estimate sound power from sound pressure using field measurements. Adjust distance, directivity, quantity, and corrections. See instant results, charts, exports, guidance, and examples below.
| Case | Method | Lp (dB) | Input Detail | Q | K (dB) | n | Total Lw (dB re 1 pW) |
|---|---|---|---|---|---|---|---|
| 1 | Distance | 78 | 1 m | 1 | 0 | 1 | 88.99 |
| 2 | Distance | 82 | 2 m | 2 | 0 | 1 | 96.00 |
| 3 | Area | 76 | 10 m² | — | 1 | 2 | 90.01 |
| 4 | Distance | 90 | 3 m | 4 | -1 | 4 | 109.54 |
This calculator supports two common estimation paths. The first uses measured distance and directivity. The second uses an equivalent measurement surface area.
Distance and directivity method
Lw(single) = Lp + 10 log10(4πr² / Q) + K
Surface area method
Lw(single) = Lp + 10 log10(S) + K
Multiple identical sources
Lw(total) = Lw(single) + 10 log10(n)
Estimated sound power in watts
W = 10-12 × 10Lw(total)/10
Here, Lp is sound pressure level, r is distance in meters, Q is directivity factor, S is measurement surface area in square meters, K is any applied correction, and n is the number of identical sources.
Sound pressure level depends on where you measure. Sound power level describes the source itself. A louder reading farther away implies a stronger source than the same reading taken closer.
For the same measured pressure, a larger distance means the source had to emit more energy to produce that reading. The distance method accounts for spreading over a larger spherical area.
Q represents how strongly the source focuses sound in one region. A free source often uses Q = 1. A source near one or more reflecting surfaces can use larger values.
Use it when your measurement procedure already defines an enclosing measurement surface. In that case, the area term replaces the distance and directivity term in the estimation.
Identical independent sources do not add arithmetically in decibels. The calculator adds 10 log10(n) to the single-source sound power level to estimate the combined total.
K lets you apply a known adjustment from your measurement procedure. It can represent environmental, setup, or standard-based corrections when you already know the required decibel offset.
No. This page is useful for planning, screening, and quick estimation. Formal compliance work should follow the relevant acoustic standard, instrumentation rules, and measurement protocol.
Sound power level is referenced to 1 picowatt, written as 1 pW or 10-12 watts. That reference is standard for reporting acoustic sound power levels.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.