Tools needed : A glass/cup half full of water

Step 1 : Open the hood and start the engine
Step 2 : Take the water cup in hand and position yourself at the front of the engine (passenger side of the car)
Step 3 : Dribble the water onto the drivebelt just past the steering pump.

If the noise abruptly stops it's the belt that needs changing.
This works on any car, not just caddys.