I am going to have the carpet replaced. I thought there was some material made to go on the floor under the rug to cut down on road noise. I thought it was called Dynomax or something. Any help would be appreciated. Thanks. Bob.

 

The product is called "Dynamat", but there are multiple grades of the material. It works well, but is not the most sophisticated material. It works mostly by adding weight to the panel, which lowers the fundamental vibration frequency of the panel below audible. More effective materials are those using a heat-cured adhesives and an outer skin as a sheer layer. However, the work required to do this would amount to a total PITA for the consumer.

FWIW: I used to work in R&D for a Tier-1, formulating these asphaltic damping materials for floor, firewall, and pillars of all Big-3 OEMs. The science behind them is actually quite complex, and requires sophisticated spectrum analyzers and environmental chambers to measure the effects. Still, it truly is amazing what they charge for their product. The last material I worked on was an expanding damping compound which was heat staked between the two layers of metal in the firewall/body, which 'blew' to fill the voids when the body entered the bake booth. If memory serves me correctly, the raw materials cost us about 42 cents / lb. We sold it in sheets to the OEM at about $1 / lb. Dynamat costs something like an order of magnitude more than this, and isn't as sophisticated. Still, I'd rather buy $150 worth of the stuff than try to mix, calendar, and bond the product myself.

On a 5000lb truck, even 50lb of Dynamat is negligible for street-going vehicles.