Saturn Repair: loud whining noise on 95 SL1 while idling, serpentine belt tensioner, road speed

Question
The noise first occurred when I was sitting at a stoplight with the engine idling.  As I mentioned, the noise gets louder with engine speed, but goes away once the car reaches about 15-20mph.  It will come back at low speeds or if the engine idles again.

The noise is a high pitched squeal.  The type that I would associate with a problem with a belt.  I just wasn't sure what would cause the noise to go away at road speed.

Thanks.

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Followup To
Question -
I have a '95 SL1 with about 160K miles on it.  The car was running with no problems until today when the engine started making a very loud whining sound when I was at a stoplight.  The noise got louder with engine speed, but would stop when the car got to about 15-20mph.  The car has a 5 speed manual transmission and a 1.8L 4 cyl. engine.

Any help appreciated.
Answer -
Sam,
 Can you describe the noise in more detail to me.  What was going on when the noise occured?  Any and all info that you can provide me will help.  

Chris

Answer
Sam,
 It sounds like your serpentine belt tensioner is going out.  This would cause the belt to slip and squeal.  As your engine spins faster the tension on the belt evens out (both on the "pulled" and the "pushed" side of the belt).  At slow engine speeds more slack is produced on the "pushed" side of the belt.  If your tensioner is loosing it's tension, you will probably find your squealing noise at lower engine speeds.  Hope this helps,

Chris