2009 GMC Sierra Whine noise

When I start the truck everything is normal. When I put it into drive, it has a small whine to it. When I press on the accelerator the whine somewhat goes with the RPMS, kind of like a super charger whine, but more dull and a deeper tone. Does this in reverse too. There is no rattling, no shaking, no grinding. Going down the road I can gas on it slightly and the whine will go with the rpms but when I back off the throttle the whine will immediate back off; a fast decrescendo. The sound appears to be comming from closer to the front of the truck, not near the rear. This problem started maybe around 45,000 miles and overtime has gotten louder, but it seems as if the volume of the sound has capped and has just remained constant now.

There is no whine in park and no whine when I turn my steering wheel in either direction.