I own a 2009 Punto Diesel. I was fairly happy with the Stock sound proofing in my car, ie., until I sat myself in a 2013 Punto. The sound insulation in the new car is unbelievable! My car feels like a tractor in comparison!! I now plan to go the DIY way to boost up the sound proofing level in my car. I've identified the 5 doors, spare wheel well and firewall as potential areas to sound proof. I won't tamper with the wheel arches, roof, floor ( I have the rubber matting on the floor, so don't want to tear it apart ) unless it is absolutely necessary. Also, I don't want to go the Dynamat or other off the shelf product way. I plan to use neoprene rubber pieces as mass dampers (on the bare metal surface), followed by a closed cell foam layer (the dark grey coloured one commonly used in packaging) as absorber and finally another layer of neoprene sheet as a barrier. Am I heading in the right way? My logic says that 2 rubber layers enclosing a foam layer in between is correct as it'll keep the outside noise away, at the same time retain the 'inside' sound.