What your hearing is the exhaust flap closing and opening. Your sounds to be a little extra loose.
What you can do to cure this problem is the 'golf tee mod'.. This will disable the valve from opening and closing. I have disabled my valve since i bought my car, i pinched the black wire that goes to the actuator on top of the exhaust tip that was in the video, and zip tied it. This stops air going to the actuator, hence stopping the closing/opening action.
Or tell the dealer that your valve for the exhaust is bad and see if they will warranty it, problem not.
Current: LCI ///M5 || ML63AMG || 13' Porsche Panamera S