2015 Macan S
Interesting. Natural resonation is plausible, however unlikely to cause intermittent vibration. I would assume it would be constant (based on RPM).Just back from a 3000 mile trip and I can conclude that it isn't the wheel bearing as the sound has not changed. It did become a knocking sound on a really rough section of road for a short while which makes me suspect that the exhaust pipe is the culprit.
I think the whole pipe is oscillating or moving and this constant movement creates this annoying sound. All the brackets are fine but the rear part of the system does have a fair bit of movement anyway.
I'm going to swing by a good exhaust shop in the new year to see what they think.
Have you checked for play in your axles?
How old are your tires?