RSR

I have a 95 SR5 that I'm in the process of sound deadening -- I've just replaced all weatherstripping thus far and they've made a load of difference. But there's still a direct noise funnel in the SR5 design, and that's the rear body vent.

So for the rear quarter windows' weatherstripping replacement, I had to remove all rear (back wall before sides) paneling.

On the paneling, it's in the bottom rear corner behind the seatbelt:


And closeup:


Full quarter panel wall with panels removed:
-The whole bottom of this section is open -- can slightly see the yellow foam insulation that ends right blow the support beam (right behind the speaker wire in the pic).

Closer up of the vent hole:

-The vents right behind the metal panel you see there at the hole -- so airflow goes down - back - up

And the exterior vent hole (size is maybe 4" long x 2" wide):

-can't see it too well but immediately between the bed and cab.

*Should also note that this cavity below the speaker box does contain the rear sunroof drain and is exposed to the elements -- humidity, dust, dirt, etc (cleaned a bunch of funk out of here when I had panels removed).

So I'm looking for ideas on how to actually soundproof this feature. I thought about possibly like an air filter foam between the panel and the frame hole, but unsure of how effective that will be as it'll have to be fairly thin. Open to other ideas. Dynamat might work to make the whole cavity not an echo chamber, but I'm guessing the reason that Toyota stops foam and Dynamat behind speaker box at approximately the seat/box level is due to moisture issues. So not sure here.

Help and any ideas are appreciated!

RSR

Any ideas? bump