Or just loads and loads of heavy Dynamat
What's funny is the Caliber is supposed to have a noisy engine, but I never hear that thing while I'm driving it, it's only noisy from the outside. And it's not that loud of an engine either, it's just noisy.
Now the AMC Straight 6 in my Jeep... I don't know how I'd not hear that beside more speaker volume. I like it's noise though. It's pleasing at highway speeds.