Liz what you have is combustion air grills. By code for every 1000 BTU there needs to be 50 cubic feet of air space to provide enough oxygen for proper combustion. It can come from other rooms via grills like you have or it can come from outside. Anther option would be to get rid of the noise 80% furnace and replace it with a 90% the brings in its own combustion air from outside.