Word of warning.
Recently I was riding as a passenger in the smart with my wife driving while we were out doing some shopping.
We had already done our wallyworld Christmas dinner shopping and had to make another stop for some more stuff.
As we got out of the car I closed my door while the other door was open and It sounded really different. I thought it was because I rarely close one door while the other is open so it didn't have the tight seal on the car.
When we came back to the car I noticed the Window was down. Car was still locked and the groceries were still in the back, but it was a bit freaky.
I must have bumped the window button on the way out. Since its Auto Down and rigged to work without the key, a simple bump while exiting opened the window without me noticing.
SO, If it sounds different when you close the door than your used to, check and make sure your window is still up.