I have heard it said that the difference between a Lexus in a Camry is about 300 pounds and sound deadening. After years of experience of applying these products. I would have to say that I agree.
Even a small amount of damping material can have a profound effect on noise reduction. In a typical application, applying damping material to the doors of your vehicle can reduce road noise up to 6 dB! This is a huge reduction in noise. Complete coverage for an average vehicle can reduce road noise as much as 18 dB!