use blue painters tape and seal the door crevice all the way around. See if noise goes away. Then remove a small portion at a time of the tape to see when noise comes back. You can also tape the inside of door to further locate the trouble spot.

Also depending on model, bent exhaust heat shield bent down into the airflow underneath the car can sound like a bad rubber door/window seal or bent body panel.

On my c-class door rubber stripping is easy and cheap, But it is the preparation. cleanliness and proper application of adhesive that makes for a good job