SPL competition is a Car audio Sound pressure Level Competition. So you compete by trying to keep as much sound pressure within the vehicle as you can the dynamat reduces the amount of DBs lost within the vehicle as it also keeps things like road noise outside of the vehicle. My reasion for install was for competition. I still have my roof and floorboards to do but my doors were the first to try with this stuff. My Trunk floor and rear hatch was done with fatmatt when I was doing my system install so I cant say how much of an improvemt was done when that was installed first. I think a 1 DB gain is a good improvement. I think with dynamat you do your entire vehicle for a 3db gain so maybe after my roof and floors are done I can acheive that.