Audi Hums a Bad Tune
This bulletin applies to the 2012 Audi A5/S5 models. A humming or metallic rattling noise may be heard from under the vehicle, mostly during engine idle or slow acceleration.
The noise may be coming from the exhaust system due to movement in the rear mounting of the exhaust system’s rear silencer. Reducing the tension of the silencer mount should fix the problem.
Loosen the mount at the rear of the exhaust system, and re-tighten the mount while pressing it together with a pair of pliers.