Odd noise from engine

[Captnbr at aol.com (Captnbr@aol.com)]

Well this noise that I have is getting louder.  Engine runs and pulls fine.  
Take two hammers, one in each hand and tap them on the concret and thats what 
it sounds like at idle.  Now tap them faster like your playing a snare drum 
but do it lightly then do it hard, then back light again and so on, and thats 
what it sounds like when I rev the engine.  I open the hood and I can't hear it, 
I can only hear it from inside of the car with the windows or door open.  And 
when I'm driving next to a wall I can hear it good too. I can't figure out 
what it is.  Anyone?


Brian 86 16v
98 Jetta GLX Vr6