What is this hole in backwall behind plastic?

I pulled out the plastic bins behind rear seats of Crewmax for a subwoofer box build. I noticed this piece that has holes to outside covered by thin plastic flaps. It seems like this might be a big source of outside noise while driving.

 

I am guessing its to let air out of the hermetically sealed cabin when you have the HVAC system set to pull air from outside. How else would the HVAC be able to push fresh air in, it would pressurize the cabin otherwise.

 

I was told by a Toyota mechanic it is for air circulation and pressure relief when you close the doors so it doesn’t pop the front windshield seal. My 2002 Ford had them so not a new technology.

 

There is always some type of venting for the cab, normal stuff.

 

Yep, I worked in a Toyota factory - all vehicles have them to prevent over-pressure when closing doors and stuff. If you didn't have that and slammed a door, the people inside would feel like their ears were punched in.

 

Thanks for the insight!

 

I figured my door seals would have been enough to let the pressure escape.

 

Same. I understand the logic, however in custom car audio installations it is standard practice to seal up holes like that with CDL / butyl rope. If the pressure were a real world issue that blew seals, caused ear pops, etc - it would have surfaced already. I will be removing that part and sealing that hole in mine.

 

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If you close it and develop a water drip on your front grab handle you might need to reseal the front windshield and we will all learn something valuable. The thought of it makes me nervous with others reporting front windshield leaks without mods.