Rattles in door glass-Both D & P sides

Hi. I was hoping someone has a quick answer for me before I drive into this problem.
I have a 73 Dart Swinger and both the drivers and passengers door glass rattles really bad while the windows are up. Metal to Glass sound.When the windows are down it dosent rattle, just when they are up. Hoping someone has an easy fix or information on this before I tear into it.
Thanks.