Dell actually has a section where all of the "environmental" specs of their systems are provided. Inexplicably hidden, from my POV:
http://www.dell.com/content/topics/glob ... =en&s=corp
To find it, you have to go... dell - about dell - commitment - design for environment - product data sheets ---- not exactly intuitive.
Anyway, these data sheets include BEL (sound power) and dBA @ operator position SPL measurement. The latter corresponds to a distance of about 0.6m. Compared to the SPL at 1m in a normal (quiet room), these will be 1~2 dBA higher. Noise is measured at idle, and with various drive activities -- but not at full load.
If you look through all the desktop data sheets, you'll find that most average ~30 dBA at idle. This means about 28~29 dBA as SPCR measures it (@ 1m). A handful are at 28~29. A couple are as low as 25 dBA. Now those 25 dBA ones should sound pretty quiet in any environment unless the noise quality is terrible.
No comments about what they'll do under load.
I suspect the Dells would ramp up and down more in noise level and quality than PCs made by quiet obsessives like so much of the SPCR crowd (or SIs like End PC Noise). Would probably depend partly on what options are chosen for the particular model. IE -- if you choose the most powerful CPU and vidcard, then you can expect great ramp up/down, and perhaps a higher base noise level that spec'd -- because the specs are usually for a base option model.