What does a whinning or humming noise mean while your driving? on 2002 Ford Escape

What does it mean when u hear a whinning or humming sound in your engine?

Asked by for the 2002 Ford Escape
If it is a 4-cyl engine,the most common cause is the belt tensioner pulley.It also is dependent on vehicle speed or engine speed.Does it make the noise when sitting still and revving the engine? It's all a process of elimination.
It dosent make that sound while sitting still just when revving the engine or driving.
is it a 4 or 6 cyl?
6 cylinder
I agree with bmdouble, remove (have the belt removed) and run engine to see if the noise is now gone. If so there is a problem with the belt drive/driven system. Turn componets by hand (key off) to see if anything shows up. Feel, look & listen while turning.