Whining noise on 2006 Chevrolet Avalanche 1500

I have a whining noise whenever i rev my engine in nuetral or whenever i accelerate. Seems to go away aat high speeds but i think the whine just gets too high pitched to hear. 2006 chevy avalanche 5.3

Did you find out what is was? My truck is doing the same thing..

Update: It was the alternator on my truck..