whats that humming? i dont have a supercharger!

[bates]

Help! my engine(stock) akes a whining sound exactly like that of a turbo or supercharger when it revs over about 3500-4000 rpm. this sound sorta scares me! can any of yall tell me what it is??

 

[jimbo74]

sounds like either a vacuum problem or could happen if you have even a drop in high performance filter..... most explorers make a whine about that engine speed due solely to the fact that it is a big v6