You know the drill. Your car stereo sounds great in the parking lot, but start driving around town and it leaves something to be desired. The overall volume drops, the highs get muddy, and the bass all but disappears. You can turn it up to compensate, but as soon as you merge onto the highway it just gets worse — so you're forced to crank it up some more. By the time you get home your ears are numb from the pounding and your music has lost that crisp edge.

Hustle out to your car the next morning, turn the key in the ignition, and your radio is loud. How loud? Loud enough that you just about jump out of your seat. What gives? Chances are, road noise played a part in that heavy volume knob, sapping performance from your system and unnecessarily abusing your speakers (and your ears).

It can come from all over — tire hum, engine whine, wind, exhaust, and assorted body rattles — but road noise is universally irritating and can make any custom system sound like mush in no time. At its most basic level, road noise is the product of vibration — outside sounds vibrating your door panels and passing the vibration on to your eardrums. In a closed environment like a car, that's a lot of vibration, and a lot of noise to compete with your music.

The good news is that you can cut down that road noise dramatically by installing a sound-dampening product like Dynamat. These noise deadeners work by absorbing sound-causing vibration energy, eliminating speaker resonance, and baffling out excessive sound. And since they work as converters rather than simple noise blockades, a little goes a long way, saving you money and installation time.

And given the dramatic effect it can have on your sound system, Dynamat is surprisingly easy to install. Here's a look at how it went adding a complete door kit to a 2002 Nissan Xterra.