Living in Western Canada and near the mountains, we've experimented with a few things to cut down on the COLD AIR swirling from the back through to the front. Not so much a problem with the noise, but it can get pretty cool!
We've found anything blocking the air movement between the seats helps a lot.
A small duffle bag (if going on a trip) or even my FB jacket across held in place by putting the arms pinched under the headrests. NOTE: Remove jacket first
If you position the jacket right, the logo looks pretty good while driving too.
This is an easy, non permanent, way to combat that cold air flow.
I agree with others that have said the back seat is no place to be on the highway in a vert.