Recent increase in traffic noise

[kck7]

For the past few weeks I have noticed more noise from the driver's side environment on my 10 month old X5D. By this I mean when a car passes going the other direction on a non-divided road, or overtakes on the left. I have tried listening for this on the passenger side and it is definitely less.

I looked over the window and door seals and everything looks ok, nothing out of place, same as on passenger side.Yes the window is tightly closed :-)

Wonder if this has been experienced by any others? Am concerned if I take it in, since this is a very subjective thing, they'll simply say "normal". But I have pretty good hearing and this is not in my imagination. One of the things that turned me on to this car during the pre-purchase test drive was how quiet it was on the road once the engine reached cruising speed.