Alternator noise?

B6/7 S4/RS4
#1

So today while driving about 60mph or so and about to get off the highway I heard some whining/humming noise which initially i thought was the song on the radio, but after turning the volume down and then turning radio off, it didnt go away. Sounded like it was coming from speakers or something. When i gave it gas, the pitch increased with the RPM’s.

From searching around it seems like it could be related to the belt tensioner and the serpentine belt itself, I assume mine looks to be on the way out as seen on the pic attached.

I bought the car CPO on 7/21/2011 with 42682 Miles, so about 7 months of ownership, was the belt suppose to be replaced when car becomes CPO? could it be that the belt got this bad over just 7 months? I just crossed 63k miles today.

Also, would the belt be covered under CPO warranty?
What about belt tensioner?

Thanks in advance!

EDIT: Happened again and I got a video. Didn’t go away when shutting car off but it went away after I drove a bit
Videos
http://s114.photobucket.com/albums/n245/Coderedpl/?action=view&current=VID_20120312_151200.mp4
http://s114.photobucket.com/albums/n245/Coderedpl/?action=view&current=VID_20120312_150801.mp4

#2

(Throught the speakers) If it happened with the volume down but the radio still on I would have guessed at an amp not being grounded properly or a loose ground wire somewhere.

That was ruled out - my next thought would be belt & belt tensioner.

3rd - pulley bearing or hub bearing.

#3

So I just got my car back from the dealership after it being there for about 2 weeks for various things. One of the things I listed was a whine I got. So they replaced the alternator, and some seal, and also the belt since I requested it (it was worn already)

…so today I’m on my way back home and I hear the damn noise again!
I DO NOT have an aftermarket radio. OEM RNSE and all OEM speakers.

It sounds very close to this:
http://www.youtube.com/watch?v=RJoaCywHjlg&feature=related

And here are some videos of it before:
http://s114.photobucket.com/albums/n245/Coderedpl/?action=view&current=VID_20120312_150801.mp4
http://s114.photobucket.com/albums/n245/Coderedpl/?action=view&current=VID_20120312_151200.mp4

and from just now:
http://s114.photobucket.com/albums/n245/Coderedpl/?action=view&current=VID_20120331_010022.mp4

What I did notice on the invoice is that they DID replace the alternator, and they did replace the belt, but they did not replace any tensioners.
Could that be it?