Sound pressure Lp and sound power Lw are not interchangeable

Know which quantity you are comparing

Sound power level, Lw, describes the acoustic output of a source under stated operating conditions. Sound pressure level, Lp, describes the sound at a particular position. Both use decibels, but they have different reference quantities and cannot simply be compared as if they were the same measurement.

Follow the transmission path

When I assess HVAC noise, I look beyond a single catalogue number. Distance, room absorption, directivity, duct attenuation, breakout noise and the installation all influence the result at the listener. Octave-band data is often more useful than a single overall value when selecting attenuation.

My practical rule is to check what was measured, where it was measured and under which operating conditions. A low catalogue value is not a room-noise guarantee. The design needs a source, a transmission path and a receiving-space assessment.