I've installed Lobocrud's insulation in my cab walls, roof, doors, and firewall and hushmat on the floor. It is reasonable quiet (I can hear someone talk) until I get t0 65-70 MPH, then I get a loud howl (can't hear anyrhing) that sounds like it is coming from air being trapped under the windshield visor. Anyone have this problem and how did you fix it. I've seen the visor louvered and/or drilled and I assume that helps but I don't want to do that. Appreciate any ideas.