How much level do you lose when distance doubles?

About 6 dB for a point source in free field, or about 3 dB for an ideal line source segment.

SPL Distance Calculator

Inverse-square law SPL loss and combined level from multiple sources.

SPL at reference distance (dB)

Reference distance (m)

New distance (m)

Propagation

Number of identical sources (coherent sum)

How the SPL distance calculator works

Enter SPL at a reference distance, new distance, propagation law (point or line source), and number of coherent sources. The tool applies inverse-square (or cylindrical) loss and optional power summation for identical sources.

Key terms

SPL (sound pressure level) - loudness in dB relative to 20 -Pa.
Point source - ?6 dB per distance doubling in free field.
Line source - ?3 dB per doubling (e.g. long line array segments).

Frequently asked questions

How much level do you lose when distance doubles? About 6 dB for a point source in free field, or about 3 dB for an ideal line source segment.