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Sound Insulation

9947 Views 21 Replies 9 Participants Last post by  dtlee
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.

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Nice summary of what people have done so far, kedge, thanks. My comments:

Futon mattresses are made from alternating layers of egg-crate shaped sheets of foam, cotton padding (I agree this is what it looks like Figgy used) and a polyester fiber such as Hollowfill from DuPont.

In mid-install of my ShoeBox subwoofer I drove the car across town to do some shopping, with all the rear carpet removed. The increase in noise was amazing, so I figured post-install it wouldn't hurt to add some sound insulation. I cut up old backpacking foam mattresses to fit under the rear carpet, in front and back of the cargo bin, and underneath the cargo bin atop the spare tire.

I also have wider (185/60R14) and quieter tires.

I suspect the cargo mat (shown here) would also help to damp sound from the rear of the car.

For those who have done door insulation, how much work is it? I am thinking of a dynamat-type solution on the inner surface of the exterior door panels, if possible. InsightCentral has excellent directions on removing the door panels but does not go beyond getting the interior panel removed. Judging from these pictures it looks like there is more work to get deeper into the doors (towards the exterior of the car from the inside). Also, that set of pictures shows that the moisture/water barrier on the door has been removed (a plastic sheet that is sealed along the still-visible white glue line in the top right picture). I have had problems with door modifications in the past (dealer repair to window regulator to fix auto-down issues on driver's side) that didn't reseal that barrier properly later leading to the infamous "wet seatbelt" issue, plus the eventual water damage of a speaker, and would rather not have it happen again.

Is there a way to do door sound insulation without removing that plastic? If so, how? What did you guys do? If not, what did you use to reseal it?
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One more question. If you stand at the rear of the car, facing forward, there is a large cavity to the right of the metal IMA box and forward of the install location of a shoebox subwoofer (which sits to the right of the cargo bin).

Anyone ever consider stuffing that area with sound insulation? Are there vents back there going into the IMA that would be blocked?
xcel said:
wouldn’t the Insight Cargo Mat accessory do just as nice a job then?
I speculated as much on the first page of postings here.

If you pull up the rear carpet and the cargo bin the next thing you will see there is the bare metal underbelly of the Insight. I think that is why adding any kind of insulation to the back area makes such a big difference. The 1/2" foam material I used is qualitatively similar to the "DynaLiner" product.

Similarly if you remove some of the sheet metal panels behind the passenger seat and to the rear of the car, you will see bare metal. Rick, I wonder if that is the area you referred to as the "dead navi brain" space, which I asked about earlier?
Rick said:
You need something up against the outer panels to absorb the noise.
Good point. This is also what I was hoping to do with the doors, but it looks like quite a bit of trouble. Perhaps when I find the time I will instead go after the floors, since I need to do some audio cable management anyway.

Since I have a shoebox sub, I obviously don't want to fill that space, but I am still curious about the space forward of the shoebox between the IMA and the right side of the car as another candidate for acoustic insulation.
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