Hey! I`ve tried to buy 27" iMac but had troubles buying a silent one. First that Reseller gave me was really loud. That wasn`t really the sound of air stream, but seemed that cooler touches something inside and makes a noise for every twist. They have me another one and it`s wasn`t really that silent as well. There were no sound of cooler touching something, but there is notable sound of air flow. I`ve placed iMac on solid table and temperature in the room isn`t high. I`ve download a tool that shows fan speed and it shows that they are ~1500rpm. From iMac users and according to official information on Apple site iMac`s are really silent or dead silent as some users described it. So, maybe something changed with latest models or I just had a bad luck? I have sensitive hearing and I can`t accept computer with notable hum, so this was one of main reasons why I decided to get iMac.