I have a 2000 Oldsmobile Intrigue and a 1999 Chevrolet Silverado 1500. They are not quiet on the inside. Lots of air leaks and stuff. I just don't understand how people hear other loud vehicles going 70MPH or so. I have good hearing (according to my latest hearing test) and unless the loud vehicle is extremely loud (like big truck with a jake brake) then I've never hear the neighboring vehicles in any vehicle, not just the two I currently have.

Edit: If I'm able to hear them, it's immediately after they have passed me.