I'm having the same issue, what year is your car and mileage? I have been told its the gearbox.
its like a grinding noise as I lift the clutch in 5th and then if I cruise about in 5th and take my foot off the accelerator I hear the whine as the speed drops under 50mph
I had this from the offset with my S3. Almost sounded like it was coming through the speakers and only when in 5th gear. I thought it was normal until I drove in another couple of S3's similar to mine. I was still just under warranty and Audi dealer had it for about 3 weeks as they kept replacing sections of the gearbox trying to resolve.
Turned out to be a synchromesh issue. Dealer said they'd of liked to just swap the entire gearbox but apparently Audi wouldn't let them under warranty so they kept taking apart and fiddling replacing till it went away.
Mind you not that I trusted the dealer one bit. But basically if it's the same thing, I don't think it'll do any harm, but if it drives you crazy get someone in the know or a trustworthy dealer to check out the gearbox.
Hi there. I have came across the same issue on my 2009 A3 Quattro. There is no whine when in 5th gear but when releasing the clutch there is a noise. I was wondering if you got discovered a solution for this problem.