it could be anything from a damaged engine mount to bearing on an alternator.

one thing, do a search on this forum for accessory belt tensioner or BELT TENSIONER.

If you have a stethoscope and are extremely careful you can listen to alternator, belt tensoner, water pump.


When you mention closing the front doors and hearing it I think windshield mounting or door straps even hood latch or inside rear view mirror.

Hopefully I mentioned some items you can eliminate.

Lots of times a helper who can listen to the car from the outside as you drive by can clue you in.