27 imac hd rumbing sound

Apple replaced my 24" imac after they couldn't solve a problem with the display. They gave me a brand new 27 inch iMac with a 3.2 i3 and a 1 tb hd. I'm hearing a soft rumbling sound from the drive, maybe every 10 to 15 seconds (maybe longer sometimes) It also makes the noise when opening up an application.

Is this normal? I've only had it today (as I write this post) and was wondering how many others have had this. The machine is wonderful otherwise. But I don't have this problem with my MB Pro or my old 24" machine -- that was as quiet as a churchmouse.

The noise, as I said, is soft and not particularly annoying (at least not yet) But I'd really like to see if there's a problem. I went into the "about this mac" and looked up the serial ATA and saw that the model is ST31000528AS. Can anyone tell me about this (brand, etc)

Congratulations on getting a new 27" iMac in place of your 24" model. That was quite a swap! Regarding the rumbling you hear, it may be normal. The 1TB drives have more platters closer together than most drives and may be a bit noisier. Live with it for awhile and if it gets worse or begins to annoy you, take it on in to Apple and let them look at it. Make sure you keep your backups up to date just in case.

That is normal from hard drives-- they are a mechanical moving part afterall. It is likely that you're hearing it only now because it's a large capacity workstation class hard-drive embedded in a unibody all aluminum chassis that would only amplify the noise.

That's the HD doing it's work and completely normal..the sound should be fairly subtle and infrequent (unless you're doing something that specifically has to write to the HD)..

Regards