Case side on: Sounds like someone in the next room with one of those big honkin' hair dryers, doin' their hair.
Case side off: Sounds like someone standin' behind you, doin' YOUR hair.. ???
Yeah, they're kinda loud. The first night I plugged mine in, my wife was watching TV down the hall in the living room. She could hear the Delta over the TV!! I went wandering thru, headed for the kitchen at one point, and she looked at me and asked, "What the heck are you doin' in there?"
Um...yeah, they're kinda loud...tee-hee-hee Cool the Hammers of Hades, though. =)
Its mainly the pitch that creates its loud and piercing qualities. That's why many people can't hear over them very well. If it were to drop, I'm sure people wouldn't complain about them as much. Vibrations can add to its noise, but they are usually easy to remedy
If you do the silicone trick its not that bad, you can find this out in the tips section. Ive done it to mine and its about as loud as a cheap 80mm case fan. [very tolerable] the vibrations are the biggest part of the noise and once you do the silicone trick all you will hear is some air noise, oh and thats with a duct coming straight off the HSF going to the sidecase cover which amplifies the sound.
I got a delta on my Globalwin WBK38.. I could hear it clear across the office, with the case on. Pretty much 50db worth of high pitched noise I could do without. Shortly after installing my Globalwin, my Delta threw a blade, solved that problem.. Got 4 other heatsinks..
My Delta isnt very high pitchesd it just sounds like your in an airplane...
I tried the silicone trick, but sadly i didnt hear any difference. If you keep your case on it wont be that bad. If it is for an office computer i wouldnt reccoment it, but if its at home where you can listen to music or play games then you wont even notice it.