I changed my alternator pulley, as my clutch was slipping on it. Made a whine a bit like that while driving.
I removed my aux belt and ran the car for a seconds and the noise was not there, i checked the play on the tensinor and that was ok, so being in the middle of the range for life on the pull (60,000-80,000 miles) i had a stab and it was indeed that.
Hope that helps.
Youtube the noise, see if any match up with your noise.