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Sound Dead

I ripped down the car, added 100lbs and over $600 of insulating materials, liquid sound deadener, and butyl mat dampener.  I've also added layers of closed cell neoprene foam, and a 1lb per square foot open cell foam/vinyl barrier to the entire floor of the car.

I am confident when I am done taking the fenders off and finish them along with touching up the wheel wells I will have the quietest 2006 Mazda3 out there...  I will soon have SPL measurements to show the difference from before and after for ambient noise at various speeds.  Smile

The white "snow" like stuff you see is an acrylic based dampening coating that has microscopic vacuum beads which at minimal thickness offers partial insulation "R" values.  After a long ride I can put my hand on the bare metal in my trunk right above the muffler and it's barely warm.  (Before I could almost cook an egg on top of that sheet metal)

Here's some of my pictures:






I have an 06 MZ3 GT 4-dr

I put in an order for some spectrum firewall, which is an insulation liquid dampener that can be sprayed on.  I was going to use about 80 square feet of "mat" dampener along with 5 gallons of liquid dampener applied at 2mm thick.  5 gallons should cover about 100 square feet @ 2mm.

On top of that, I was going to cover the floor with a barrier called luxury liner.  This is vinyl over foam which acts as a sound barrier.  There are 3 factors in sound control.  Absorption (foams and composites), barriers (usually lead or vinyl septum combined with foam), and then Dampener (Butyl or asphalt mat dampeners or liquid dampeners).  A fourth factor I guess is thermal insulation if you use an insulation additive with the liquid dampener.

5 gallons of insulation liquid dampener (Has microspheres similar to hytech paint insulation additive or cascade temp-coat)
80 square feet of mat damplifier, 18 square feet of luxury liner, and a spray gun.  Shipping is $70 from AZ to CA for all of this and I think retail is about $500-$600 or so.

There might be a forum member discount of 20% off for the mazda3forums, I'll have to talk to the owner Anthony...  The website had a make over not too long ago and prices have been changed.

I found that it's common for the protege and mazda3 for "rock" pinging in the wheel wells.  This can be an easy fix with spectrum sludge which can be an under body coating as well as vibration dampener.  I might do that to mine eventually.

Liquid dampener does have a better bang per buck ratio, weighs less than mat, but has to be put on "THICK" to get the same performance as mat.  Putting on mutliple layers takes time.

I've experimented with dynamat extreme and cascade audio's vinyl dampener and have had great results in my toyota 4runner.

Basically it will make "metal" panels sound like cardboard, reduce ambient driving noise...  however, I'd recommend that people treat the WHOLE car and not just one part.  If you just treat 2 doors, then the other 2 doors will be loud.  It's common to fix ONE area only to notice a new loud area you didn't notice before.

A budget of about $500 can really quiet a car, and a budget of $1000 will get you that top notch high end luxury car quietness.

People tend to tear out everything exposing as much of the firewall as possible all the way to the trunk exposing the metal and OEM thin black dampener.  Clean the surfaces, then apply mat over the existing dampener.  Then apply spray on top of that, then perhaps foam such as overkill or luxury liner.

For rattles, use foam gaskets like "rattlepad" from secondskin, or Cascade audio also has a closed cell gasketing material as well.

Here's my quick coverage estimate for a Mazda3 sedan:

4 Doors - 40SF
Roof - 15SF
Floor - 20SF
Trunk - 20SF
Firewall - 10SF
Wheel Wells - 20SF
rear deck - 10SF
Hood - 15SF

I'd say for good 1 layer mat coverage you should get about 160SF which will run about $350-400.

Doors are the most important.  Then maybe Floor, firewall, and trunk.  Roof is primarily wind noise which isn't TOO bad.  Wheel wells is for dirty roads with rock ping noise, and the hood is for engine noise which is also not too bad on the mz3.


I removed the stock fiber insulator/hood liner pad, and installed the following:

4 square feet of butyl/aluminum damping mat.  (Secondskinaudio damplifier)
Then I installed an engine box lining foam that's lined with high heat aluminum/mylar foil.

It has a very strong adhesive and can stick on without use of the pins, but I used the pins anyways.

The foam is light weight and is like 2 lbs, and the dampening material totals up to about 1.6 lbs.

The effect is the engine is drastically quieter than with the stock pad.  On freeway I can't tell if I'm on the engine or not in 5th gear because it's all absorbed by the sound absorbing foam.

Engine idle is barely noticeable, and the engine is quieter at all RPMS.

No noticeable heat increase.  Just quieter which I find good for the freeway droning I do...

If you've tossed your hoodliner or yours gets weathered, consider an aftermarket foam liner!


Here's the break down:

Entire Floor (plan about 30 square feet)

1 layer of 60 mil butyl mat dampener 0.4lbs per square foot (damplifier)
1 layer of spectrum firewall liquid/acrylic dampener with insulating additive applied at 2mm thick or 1 gallon per 20 square feet.
1 layer of 1/4" thick open cell foam bonded with vinyl sound barrier.  (luxury Liner)  1lb per square foot put where the "mat" locations are.
1 layer of 1/8" closed cell neoprene over the rear seats and inside trunk, with a 1mm layer of spectrum firewall painted on top of this.

Roof (14 square feet)
40% coverage of damplifier
1-2mm coverage of spectrum firewall

Rear Deck (underneath) (8 square feet)
1 layer of damplifier
1-2mm of spectrum firewall

Trunk Lid (12 square feet)
40% coverage of damplifier putting strips to connect the 2 panels together.
1-2mm of spectrum firewall

Trunk, spare tire well (24 square feet)
1 layer of damplifier
2mm of spectrum firewall
extra 1-2mm of spectrum firewall over muffler areas where the sheet metal gets very hot

Firewall (8 square feet)
1mm of spectrum firewall over existing OEM vinyl sound barrier (lower half of firewall)

1mm of spectrum firewall over air ducts from under radio to under the driver/passenger chairs

A-pillars, C-pillars
20% or maybe less damplifier coverage with marginal spectrum firewall coverage

Plastic Interior Panels
Marginal coverage of spectrum firewall to the inside of plastics...  Although acrylic can "peel" off the plastic, it seemed to stick ok.

Under License Plate
Small vinyl strip of dampening

Untreated Areas include:
Front Fenders, Doors, Hood, rear fenders, and wheel wells.

It's a lot of work that isn't cheap which is why you shouldn't expect to get a job like this done in a weekend.  Smile  I plan to set aside some time in the near future to finish the installation...

I probably won't hit the hood and it's possible I won't do the fenders.  The wheel wells will be done for sure since I know that will definitely help and the doors are supposed to make the biggest change in reducing sound.  I plan to spend a whole day on doors.

It's possible to treat only specific areas to give yourself maximum sound deadening with minimal weight.  I just chose to go the whole 9 yards... or should I say about 250-300 square feet...

Basically you can do the entire car with one layer with about 160 square feet.  I'd save about 40 square feet for the 4 doors since those have two metal panels.  Hood would be about 14 square feet.

The way I divided up the square footage among the sections is just a guess since I did not measure anything out so please don't budget your purchases based on my assumptions.  I suppose a helpful thing to do would be to post exact numbers...  hehe, but I was too carried away cutting up pieces and slathering on spectrum.

More tests should be done today and i'll post results when I have the time.

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Last modified: 03/24/10