Battery light flashing and Whining sounds
 

Recently my alternator gave out and I had it rebuilt. The car has been driving fine since then which was a few months ago. Today the battery light started flashing and everytime I step on the gas I hear a whining noise. The belt was also replace along with the alternator.
Was wondering if anyone had any input to what they think it is? a pully maybe?
Its a 2005 BMW X5 3.0

Heres the video of the sound.

https://www.youtube.com/watch?v=mNueSFr-TXM

Have you tested the voltage/output from the alternator?

And FYI, the video is not showing up for me in your post

I have tested the volt, but I don't remember what it was; I just remember it was enough to be at the recommended voltage. I'll check it again.

Sorry about the video I thought I posted it.
https://www.youtube.com/watch?v=mNueSFr-TXM