So this is a sound that occurrs while the car is rolling. It happens with the transmission in neutral.

Does it happen while the car is in gear and you're braking using the engine?

Does it happen in all gears? If not, which ones?

Do you hear noise when you hit the brakes?

Does the car make the sound at a specific temperature? For example, does it make the noise after it's warmed up? Or all the time? Or some other time?

It's doubtful that the timing belt will screech if it's under the cover. Timing belts will make a flapping sound if they're loose and hitting the cover.

Is it a screech like a brake screech, where it's very high pitched and constant? Or is it a screech that sounds like a buzzing or whirring sound? See if you can track down these answers, and we'll go from there.