Whining noise when accelerating

I have a whining noise coming from the front, sounds like a supercharger but not as high pitched, and it only makes the noise in 1st or second while accelerating from a stop or slow roll (5mph) and it stops making the noise when it goes into 3rd or it goes faster than 20mph. Idle sounds fine, and in neutral there is no whine. Any ideas?

hmm, i don't use the A/C (i leave it on vent) and i still have motorcraft air filter in the stock airbox.