How to: Sound deadening mat on a budget.

[jblair]

The previous owner of my car liked to put his two big dogs in the cargo area. After extensive scrubbing, vacuuming, cleaning, etc. of the entire inside of the car, I determined that the rear cargo carpet needed to be pitched. It is stained, stinky and downright dirty. The same can be said for the sound deadening mat underneath.

I won a rubber cargo mat from a '99 Legacy Wagon off eBay and I plan to use that instead of getting new carpet. However, I wanted to have some sound deadening mat to absorb exhaust and road noise. I looked around on various Web sites for replacement mat, and all I found was expensive mat for car audio purposes (i.e. Fatmat 2'X4' floor liner for $50 + $18 shipping).

So I went to Lowe's.

What I found was carpet padding for 49 cents a square foot (or $4.50 a square yard) for the thicker stuff. The thinner stuff was about half as much, but it was too thin. Here is a comparison of the old sound deadening mat (on bottom) and what I picked up at Lowe's:



As you can see, they are about the same thickness. However, the carpet padding is much denser and has a blue plastic coating on one side.

So I used the old deadening mat as a stencil, outlined it with a Sharpie and cut away. Here is what the cargo area looks like:



It's not perfect, but it gets the job done. I purchased about two square yards, and the guy gave me a foot extra for free because the end was kind of cut up. It ended up costing me $8.82. With what I had left over, I used underneath the rear seats, as seen here:



And with the carpet in place:



I haven't driven it yet, so I can't comment on how much it helped, but I like to think that it will make the cabin a little bit quiter. There were even a few odd-shaped pieces left over and I stuffed those around the rear wiper fluid container/scissor jack storage area and around the spare tire.

[Brat4by4]

Nice! This is probably what I will end up doing in my wagon I just picked up that will have a sound system in it.

That should cut down on some of the road noise and make the back more comfy to sleep in.

[jnorion]

Be careful with that stuff... it does help keep the car quieter, but it absorbs water and holds it like a sponge. It will mildew very quickly if you ever get it wet.

[Brat4by4]

Doesn't the stock stuff absorb water, too? You just have to make sure to dry it out if it gets wet, correct?

Then maybe I won't use this stuff under the floorpan carpet. The less real sound deadening stuff I have to buy, the better. I'll have to check into getting scraps from the local audio shop.

[jnorion]

As far as I know the stock stuff is more of a fiber mat than a sponge style. That's how it was in a couple of my other cars at least... I haven't taken it out of the Subaru yet.

[jblair]

The stock stuff most likely doesn't absorb water as much, but it will still absorb water. I put the plastic-coated side up so if water hits it, it won't absorb it as much. Also, I'm getting a rubber cargo mat, so most water will be collected by that.

[jnorion]

Sorry to bump an old thread but I'm curious about the outcome of this. I'm getting ready to do some major sound deadening in my car. Does this significantly reduce noise? Is water absorption a problem?

[BAC5.2]

The "car audio guy" on the cheap method of sound deadening is using tar-backed aluminum used for roofing purposes. The downside is that it makes the car smell bad, and it melts.

I am going to order a 100st ft roll of FatMat (100mil) from e-bay. The stuff retails out at about $130 shipped for 100 square feet. That should be sufficient to cover the whole floor pan, the roof, the doors/hatch, and the fire wall, with an extra layer around the rear strut towers, and on the firewall. If enough is left over, I'll do a second layer on the roof and spare tire well.

It'll be worth the weight for the quietness of a Lexus.

[jnorion]

Yeah, I'm not interested in going cheap on that type of deadener. I was planning on using RAAMmat myself. But I want to also add soft matting as well for more insulation and to block more road noise, and there are a lot of options. I've always been told to stay away from foam-based carpet padding like we were discussing in this thread, but I've never actually come across someone who used it so I'm interested in real-world results.