Strange noise at low speeds and when idling... please help.

Hi, I have recently noticed a strange noise coming from my S3.

When the car is ticking over and you give it a slight rev there is a noise which i can only describe as a siren noise, also when you plod on slowly and change from 1st to 2nd gear and then 2nd to 3rd its also noticeable.
When the car is slowing down you can hear it pretty bad too

I have recently noticed tiny bits of oil on my drive which could be coming from the gearbox, is this related to the noise? Would the gearbox make a sound when revving even if not in gear?

It could possibly be something minor and relatively easy to repair (fingers and toes crossed) but who knows...

I dont think it is the turbo as mine is fairly new.

Any response would be so appreciated.

Matt
matthew_evans1984@hotmail.com

Yes, it is a whinning noise. Have you any thoughts which belt it could be.

It could be soo many things wrong its hard to distinguish what it is.