simple! wear ear plugs!!
i remeber one of my mates parents bought a toyota(camry, i think) and they were saying that is really quiet because it had a tar layer in the cabin and all over the under carrage and as a result it was heavier than a commodore, another fellar that owned a 1600(510) he thought of a bright idea of filling the guards with an expandable foam,the kind used by buiders. The original idea was for strength while rallying, the idea was on the off chance that he stuffed up and side swiped a tree the car would just bounce off and keep going, he comented that it significantly reduced the noise, only problem with the idea was when he finished the race he had that much gravel in all four wheel arches you could use it as road base for a drive way, there was sh#t loads, so that idea can canned. Me personally, i love the noise, i wouldn't have it any other way. From memory if you ring companies that rustproof cars, some of them also sound deaden, they might might be able help you or lead you in the right direction. let us know how you go.