Hey guys thats nothing!!
Recently flew back to Oz on a CX A340 and reported a 'flapping' sound I couldn't identify to the crew.
They couldnt (or wouldnt) confirm the cause.
Sitting down towards the rear the noise became quite obvious at slow speeds.
Turned out a slide had deployed post despatch and was flapping in the slipstream!!!!!!
Now call me a liar but its true and was reported by the crew to the authorities according to my CX contacts.
PS: Not being an Airbus jock I thought their EICAM would report such a thing as it indicates when doors are armed etc.