If someone disconnects the anti-rollbar drop links, you can freely move the roll bar up and down with your hand and feel/hear the same noise.
I lubricated mine with silicone spray but it only lasted a few months.
The bushes are not availabe from Audi as a sperate part, but if you can get after-market ones, I think you can replace them but not 100% sure.
http://www.mister-auto.co.uk/en/bush...7920_g331.html