I just received my 27" 3.4 i7 iMac with the 2TB drive this week and I can hear the hard drive in a pretty quiet room when it read/writes data. I typically use WD drives which I find mostly quiet (varies between drive) and this drive sounds a little louder than them. It is more of a low crunchy sound but doesn't bother me (I expect some drive noise and I am pretty anal about these things).
I can also hear my iMac fans running but it is more like a low whooshing white noise than anything else. I definitly don't have to put my ear right up next to it as some people claim (maybe they are hard of hearing) but again I expect to hear some sound when air is being moved around. I am comming from an old Dual G5 Power Mac that finally died (won't recognize any memory any more) which had fans that would sound like a jet taking off even when just doing something simple like changing songs in iTunes so the relative "quiet" of my iMac has been much appreciated. I have it placed on a hard surface so that may also amplify what little sound there is coming from it some. Considering I have a multitude of external drives and ceiling fan running most of the time I can probably say the iMac is the quietest thing in the room.
I'd call my system (1TB Seagate HD) pretty quiet. I thought I finally heard the fans last night, then realized it was actually an external 3.5" enclosure I left on.
I can hear the disk seek if I make the system do enough seeks (say copying a bunch of files while something else is trying to read a large file), but even then its a relatively quiet drive compared to others i've owned. Heck, the Momentus XT in my powerbook (hybrid SSD/HD) makes a lot more noise just coming out of sleep.
Maybe I'm hard of hearing like the previous poster suggested. But the iMac seems as quiet as my mini even under load. Both are *way* quieter than my PC was even in idle -- under load that thing got distractingly loud.
Glad to hear these reports, can someone compare these noise levels to previous iMacs? I think that the HD's in some of the original aluminum iMacs were practically silent to the user. Maybe they were farther away from the edge of the case?
I have 21.5'' iMac 2011 256 SSD + 2 Tb Hitachi HDD. That 2 Tb Hitachi HDD is the only source of noise in this model. And for sure this noise is well recognisable in a silent room. The read/write sounds are fine and probably better than some other drives, my problem is a constant rotational hum of this drive, which is for sure I can hear pretty well in a quiet room. People with 2 Tb HDD without SSD for sure are thinking it's a fan noise, but not. Fans in iMac 2011 are so quiet you won't hear them at all , even in a perfectly quiet room. So this 2 Tb Hitachi drive for sure has a noticeable constant rotational hum, which reminds a fan noise. But it's a drive noise. And this is the only thing I don't like in this model. I never had rotational persistent noises in my older iMacs. If somebody uses iMac 2011 in a perfectly quiet room with Hitachi 2 Tb HDD, they are welcome to comment whether they have any noise. Maybe my drive shouldn't be that noisy. Apple service does not bother, if a drive is working without errors - they don't bother. Very sad.