Resolving the cabin vent sound issue

Feel like after dampening my reg cab with dynomat on the floors, doors and back panel plus MLV pads under the floor carpet it worth it try and tackle the vents. I didn't want to block them in any way. I padded the truck pillars with closed cell foam for low frequency and then inserted open celled foam to bounce high and mid frequency. A large chunk was stuffed up top (usually covered with moisture cover) and in the middle where the plastic vent is visible (sorry I lost that photo) which you can see in the 3M spray glue photo. The seat belt tensioner has closed cell foam around it on the plastic and I sandwiched open celled foam between it and the back panel (again sorry lost that photo). Happy to report it was a pain in the ass but I'm its quieter and I can't hear silly little sounds like bikes passing or people walking by. Hopefully it takes care of road noise as tractor trailers are insanely loud in these trucks. Worked for me. Hopefully it works for y'all!

 

I did something similar. I also sprayed the pack of the panels with rubberized undercoating to add density to them.