I had a late 2009 21.5" iMac with a 500GB hard drive and I could barely hear the drive at all. The entire iMac was pretty much silent. Even the fan was whisper quiet. My new 2011 21.5 iMac with a 1TB drive is very easy to hear. Much louder than the old one. I can hear it accessing even with ambient noise in the room. Not a big deal but I was wondering if anyone else noticed the difference.