IMac :: How Much Computer Noise Should You Hear?

i have had my imac little under a week i been looking for any faults so can change soon as. I have 1 dead pixel, not yellow tinting, no buzz or hum noise but not sure about the hard drive it could be just me.

So how quiet should a imac be? i hear the hard drive working wen sometimes going through sites or doing program stuff nothing extremely loud though just quietish sounds that last few sec which different from the standard leave alone computer noise, which i think is normal with any computer but since i found at thread on hard drive noises i not sure now.

so question is really how quiet should a iMac be? i guess you should be able to hear it running but wen you are doing stuff should you hear the hard drive at all? just bit paranoid at moment since first mac.