I recently purchased a used '01 Insight and drove it up from Monterey, CA to Renton, WA. Two full days of freeway driving really shows how much this car needs some sound deadening. So I started looking into what others have done and posted about.
grebe and Mr. Salty have used Quietcoat's QuietCar liquid product and seem happy with the results. From Quietcoat advertising, the QuietCar seems very flexible in that it can be used as undercoating on the exterior or inside the car.
Rick (AZ) and BlueInsight1701 used .25" generic insulation mostly just laid out without glue except in the doors. This was fairly cheap and gave 4-5 dB noise reduction.
Rick Reece used Brown Bread, LComp, and foam with satisfying results. (I swear I read someone getting 8 dB reductions with this same type of install, maybe the yahoo forums)
After reading about all of this done last year, 2003, reading all of the propaganda from the marketing departments, and trying to get a sense of what is going to work well, I am leaning towards a combination of QuietCar to damp panel vibrations and generic .25" thick insulation material to absorb the sound that gets through.
Does anyone have updated information on their installs from last year? For the QuietCar installs, is the material still holding up? Has it flaked off or degraded in quality? Any regrets? Any odors resulting from installs that people are regretting now? Any changes to the insulation/damping materials installations since last year?
I plan to decide what path to take in April sometime and do the install in May along with my stereo system.