For a single piece of hardware they should give levels in Sound Power (SWL), not pressure. It's easier to calculate and there is not the same problems, becuase the power level is the power level, regardless of distance.
Better in terms of a repeatable value but definitely not easier... unless you have the gear, time, expertise. Sound power is an expression of the total acoustic power emitted while SPL is a measure of the sound intensity at a specific distance and position from the sound source.
SPL only requires a sound level meter; in an anechoic chamber when high precision and repeatability is needed. Sound power requires measuring the sound at 1m distance at multiple point all around the sound source. The resulting data is then used to calculate sound power. SWL usually requires a larger chamber.
This photo from Dell, provided to The Silent PC and posted on its ISO 7779 information page
, show's a typical Dell setup in a hemi-anechoic chamber for measuring sound power. It's a hemispherical array of 18 measurement mics so that all the acoustic data for SWL can be captured at once. (The cost of those mics alone could be more than SPCR's annual revenue.
In my experience, SWL does not have very good correlation to perceived sound; the A-weighted 1m SPL has better correlation to what I
hear. That's based on the sound power values cited for various gear by various brands -- because I cannot measure sound power in my lab -- versus the SPL I've measured for these devices over the years.
Whan i say easier to calculate, i mean that its easier to do caculations when you know the sound power of the source, as compared to knowing the sound pressure at 1m.
Sound power level is independant of size, so it is no suprise that there is a difference in what we hear, a small object with the same sound power as a large will be noisier at 1m. Besides, sound pressure is what we actually sense. But that doesn't mean sound power shouldn't be used, just as we use the power of and oven, not the temprature. Sound power is easier to caculate with, and you get none of the problems with "how was this measuered " (as long as you can assume the sound power level i actually correct). Sound pressure should be introduced when you are measuring the real sound for the people near the equipment, for instance on the work-station from an assembled PC or similar. For single pieces of equipment, i would much rather have the sound power.