I have a ton of sound deadener, in my car.
Where I get noise, being an older car, is;
#1 Wind Noise. The old windows do not seal air tight, and there is a ton of tubulent air around the vent windows, roof drip rail, chrome trim and mirrors.
#2 Engine and header noise. More solid motor mounts and headers contribute to some noise, and exhaust. I wrapped the mufflers and primary exhaust pipes with header wrap (that worked)
#3 Suspension noise, rod ends, firmer rubber bushings contributes to more direct transfer of road noise.
Only the wind noise really bothers me. Even if you have the windows down a crack at freeway speeds, you cannot even talk to your passenger. Radio = forget it. I have a/c bu my wife insists on having a window down, usually (I don't bother arguing
)