I have a 1997 A6 quattro and a couple of days ago i heard a noise while steering (even if i'm stoped). So I thought it could be the hidraulic fluid, which was low, but then i realized that the noise gets louder when i accelerate. Any idea what it could be? Thanks.

 

could be air in the steering since it was low on fluid ( the faster you go the faster the pump goes ) how to check and fix,

jack front wheels up of the ground ( engine switched off ) turn the steering to full lock both ways a few times then refill the fluid then see if the noise is still there