Automotive sound damping

I’ve been wanting to improve the sound isolation of my car for some time now. A friend has just done this to his car, but since it had been a while since I’d seen him, I couldn’t tell just how much benefit he got from the treatment. Basically, a thin (but dense) sheet of rubber-like material with a backer sheet (vinyl or aluminum) is applied underneath all the finished surfaces, right to the chassis of the car. This serves to increase the mass of the metal, thus raising its resonant frequency (reducing rattles) and providing an even thicker barrier between the road and your ears (quieting the cabin).

My question is this: What should I use to do this? I’ve seen some potential materials here, but they’re pretty expensive. Have any of you improved the sound isolation of your cars? How did you do it, and were you happy with the results? I was thinking spray rubber undercoating, as it is cheaper, but it would be a pain to control the application, and it doesn’t fill or cover holes like the sheet stuff does. What should I do?

As an aside, if I did choose to go with the sheet stuff, I’d need to calculate the amount of surface area to be treated. Is there an easier (or more accurate) way to do this than guesstimating based on crude tape measurements? Thanks very much, everyone.

I’m assuming you’re planning on doing this to benefit your music-listening pleasure…

when I was into car audio, I used to go here
these are the guys who do car audio all the time… give them a try, as well as the wealth of information you’re sure to get here. :slight_smile:

one tidbit to add to your description of how the sound-dampening stuff works. (is it dynomat?) I think adding mass to the vibrating body (panels of your car) would lower the resonant frequency, not raise it. (Hey, more bass. cool :))

the rubber backing also helps by dampening the vibration itself. It actually converts vibration to heat, in minute amounts.

just something to keep in mind, if you’re trying to come up with homegrown materials that accomplish the same thing.