I think I may have started suffering from this problem, I can hear what sounds like a moped in the distance sometimes when driving. To me though it sounds like it's coming from the A pillar direction on the drivers side, at first I thought it might be some form of lose trim flapping in the wind but then this came to mind. My Wife commented about what that noise was which is saying something as she would never normally notice.
What do you think, is this possibly the cause? I was thinking of buying some anti rattle felt tape or sound insulation tape but that seems a bit too thick to try for the fix.