I was driving today and it was quite cold outside so I had the heater on. Then I noticed that I felt cold air coming in through the door and hitting my left hand. I found out that the air from the outside somehow sneaks into the cabin through the cracks in the window switches and the inside door handle (the plastic one not the metal one). You can really feel the air pushing in. It also did this for the passenger side.

I have noticed this as well, although I'm not concerned about it. There is no noise, and I actually like the idea of an air flow through the innards of the door. Obviously assures that any moisture will evaporate quickly rather than attack the metal and cause corrosion.