There are few secrets left in rod-building, but this might be one of them: sound-cancellation mats. They are sheets of adhesive-backed, dense, rubberlike material that bond to the inside of your car's sheetmetal or fiberglass panels to damp vibration and block road noise. We've used them in everything from roadsters to truck cabs and found them to be spectacularly effective. This type of soundproofing is easy to do, and you'll be shocked at how much more you'll like your car when you're done. Treated doors will shut with a more pleasing thunk, exhaust resonance will be damped, road noise will be reduced, and your stereo will sound better.
We've used sound-killing products from both Scosche (Accumat) and Dynamic Controls (Dynamat) and like them both. The product we use most frequently is Accumat Lite in the 0.045-inch thickness, though a thinner 0.035-inch material is also available. The vibration-damping Accumat Lite is made of a material the company calls visco-elastic. Competitive items from Dynamic Controls are Dynamat Original (0.070-inch thick) and Dynamat Premium (0.040-inch thick) in a material called styrene-butadiene-rubber. Dynamat Premium contains greater inert mineral content.
Neither the Accumat Lite nor the Dynamat require heat to bond to sheetmetal, though warmth can help form the mats around contours. They stick well to clean sheetmetal (we use a grease and wax remover first), but are trickier to adhere to rough fiberglass. In theory, a single 12x12-inch square in the middle of a panel will help kill vibration, but we usually coat the entire inside of the doors and underside of the roof with the stuff. The dense sheets of matting can even be used to seal small gaps and air leaks where two panels meet. Use them on wheeltubs, too.
Both companies also make products that include a layer of open-cell foam. Accumat combines it with very dense rubber-like foam and offers it in thicknesses of 1/4 inch and 3/4 inch. The thinner version is recommended for the underside of carpet and interior panels—it's self-adhesive, and we prefer it over Dynamat's Dynaliner (0.050-inch thick), foam product that has no adhesive. However, we like the Dynamat Hoodliner, a 0.750-inch thick foam product with a heat-resistant aluminum skin, for heat reflectivity in underhood applications.
Try the stuff and you'll like it. Quietly.
