Sound Power & Distance

Datasheets quote sound power (Lw, a property of the machine); people and legal limits care about sound pressure (Lp, what you measure at a distance). Converting needs the radiating geometry — a machine on a hard floor radiates into a hemisphere and reads 3 dB louder than the same machine in free space.

Free field only — indoors, reflections raise the level and the inverse-square law stops applying beyond the reverberation radius. Doubling the distance always costs 6 dB outdoors, never the 3 dB often assumed.