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Sound Deadening FAQ


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So just BXT? You might try some Ensolite over the top of the BT to then attenuate some of that low freq. noise...


I did it in the wife's car and it really helped with the BXT.



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  • 2 months later...



Using bitumen (asphalts) mats and isolation I fixed all four doors for less than 150 $.

Used bitumen mats, 3 mm and 1,5 mm thick. Then I used isolation mats in 10 mm or 30 mm size.


For bitumen mats


200*250*1,5 mm is around 1 $

400 * 400 * 3 mm is around 5 $


For isolation


1000 * 500 * 30 mm is around 12$


The result is fantastic, it feels better than my old BMW and Mercedes and the result is great in terms of sound isolation. The overall sound level in the car is reduced a lot, the doors feels thight and feels like "quality'".


Only on coarse roads, you can still heare some noice, but I thing that is related to the isolation in the chassis.


As a great bonus, the stereo sounds a lot better !


There are a lot of space in the door sides, fill it up with isolation, up to the level of the fasterners, and a little bit more. The tighter the better in terms of rattles etc.







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  • 5 weeks later...

I just installed dynamat in all 4 doors and also installed new Polk Audio DB650s. Took about 3 hours all together last weekend. I peeled back the plastic sheet on the inside of the door on the metal (NOT the plastic door panel) and put the dynamat in there, completely covered it pretty much, and I must say, I am very happy with the results.

What a huge difference! The car is so much quieter on the roads now. Very isolated cabin. The polk's make a difference too, I haven't noticed very much change on low end response, but the highs are definitely clearer and sound more true to life. I started noticing ticks of the cone on the ride symbol and high hats more clearly in rock. This is all using the stock deck.


I'd highly recommend this upgrade.

Go Cardinals!

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  • 1 month later...
Has anyone tried putting the sound deadening material under the hood to see (1) whether this makes a substantial change in dB level and (2) whether the additional insulation would adversely affect the heat level under the hood?
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So, after almost half a year, I have sound deadening almost the whole car.

The doors are fixed, with all possible stuffs. I have also removed all the interior in the back (have a wagon).

Extra materials all over the car, I guess it's at least 30 kg in deadening materials.

Yes, It has been better all the time, but after driving my old BMW and Mercedes = STILL A DISASTER.

I think the main reason for the extreme sound level is the horrible roads here in Sweden.

Couarse roads, you havent seen it at all.


The first trip make me almost cryed.. What the heck have I bought, my first personal payed new car!!


My wife in her new BMW 320d had an very pleasant time...


So I started to deadening the doors, the wagon parts etc. At least 500$ payed in different stuffs.

Also hired a sound meter.


Data of the car is 18" wheels with Goodyear Excellence tires. First, I got Yokohama Avance or something likely named.

Sounds horrible. They replaced it with mentioned tires. Sounds as hell, still.


I think I have reduced the sound level with at least 2-3 db, but I am embarriced to take a customer for a long trip..


So, finally I find my solution:


Change wheel (the original 17" tires with Yokohama SG2 winter tires) Even if this tire is the bottom 2 of 10-12 winter tires tested, at least the $£€@@ fcn car it QUITE now.



1. If the roads are bad or like in a war condition (like here in the great country of Sweden) you cant sound deadening the road noise.

2. But if you take the time to do it anyway, you can make it a whole lot better

3. But (hate to say it) if you go for smaller wheels, and higher tires its gets a lot better.

Just let us be comfortable with that the Japanese manufactures with medium size (size $$$) cant make cars with a

low sound level droven on couarse roads (not to mention Lexus etc)

4. Change to that booring wheels you dont like, and it sounds....nothing, even less it you really have completed the point2 above.



ps 1. Will never forget the horrible, terrible trip in Stockholm in June, it was our 10th weddingday,

new car and my military service was a less hearing experience.


ps 2. all respect to Toyota who made a "swedish" road in Japan, just to eliminate the sound waves going throut the chassis.


ps 3. Pray to whatever you like, it you think your car is quite, it is because your roads are perfect.... Dont think you live here in Sweden.

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  • 1 month later...
  • 1 month later...
I just sound deadened my trunk and door panels. It is awesome! This should have been one of the first mods that I have done on the car. I have had it for almost 2.5 years! Damn, anyway I am writing because I used Peel n' Seal instead of the alternatives. I did not have a bunch of money to spend so this was well worth it. I was very impressed.
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  • 1 month later...
i just did my car with the b quiet. couldn't be happier with price, ease of use and results. i certainly would recommend b quiet to any and all, plus i manage a body shop. so i will be purchasing more of this as it costs less than the sound deadening pads i currently use for repairs to Honda, Lexus and Volvo's.
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  • 3 weeks later...
I posted this over on ImprezaWRXSTI:


Some information on sound and vibration that some of you might be able to use.

I've noticed that a lot of folks who apply, or paid to have applied, a Dynamat type product are getting a bad deal. They either just don't know how noise attenuation works or they are maximizing profits.


Here's a semi-technical explanation, from a Master's level Mechanical Engineer, on the proper way to install the stuff.


There are two ways to attenuate noise in a car.

1. Sound wave Absorbsion

2. Resonance reduction



This is when you have a fiber batt that actually traps and prevents sound waves from propogating. The thicker the batt the lower the frequency that will be absorbed. Thin batts absorb high frequencies. (The thickness of the batt absorbes up to the freqency that is 1/2 the wavelength of the batt thickness) The denser the batt, (normaly ~5 times as dense as fiberglass insulation) the more of the frequencies that are to be affected are absorbed. So dense, thick batts will absorb the most sound.


Body cavities or deap space will collect and potentially amplify the noise, much like a wind instrument or guitar. This is where this stuff works best.


Resonance Reduction

This is what Dynamat and its clones are trying to do. Every panel in the car will have a natural frequency that it will vibrate at then excited; Doors, firewalls, pillars, roofs, etc.


simply: Frequency = SQRT [ Stiffness / Mass ]


Dynamat essentially adds mass to the panels to alter the vibration charateristics of the panel. They also break up the standing vibration waves in the panels. (denser the better)


It doesn't really add stiffness, unless you make a structure and glue or bond it to the panel to increase the cross sectional area.


This is the main acoustic differnce between the tinny sounding doors of a stock subaru and the bank vault doors of a lexus.


What does this mean?

You don't need to plaster the entire inside of the car with dynamat. Simply put 1-2" strips of the stuff over about 20-30% of the surface of the panels, in a chevron, or checkerboard pattern. This will get you 95% of the sound improvement of a full application without all that wasted mass or expense. (Dynamatt is EXPENSIVE!)


In the body cavities (firewall, behind the cosmetic peices in the trunk and package shelf, etc.) is where you want to put the batt. This will prevent a megaphone effect.


You can also get a drum effect, where a closed cavity (trunk) will make a panel (seat back) vibrate. Applying either one will work there, although Dynamatt is normally easier. The batt will also stuff between a hard structure and a cosmetic panel to keep the panel from humming (like the rear parcel shelf)


All strips should be about 1-2" wide, AT MOST


So, for the most cost effective solution I would:

1. Chevron the interior wall of the door skin with about a 20-30% surface area application.2. Put a few strip on the interior door structure around the speakers.

3. A few 1-1.5" strips of the stuff on the rear shock mounts from floor to top in sort of a spiral pattern.

4. A few strips on the underside (or topside if you remove the cosmetic shelf) of the package shelf.

5. A few diagonal strips on the rear seat back and the structure around the shock towers.

6. A few strips in the trunk bottom and side walls, but not too much.


Probably 20-30 square feet AT MOST for all of this. (it goes fast) Which will add like 6 pounds to the car.


This should get you 90% of the benefit of a full application with minimal cost and added weight.


If you are brave you can take out the headliner and the dash to get to the firewall. An X or >> pattern in the roof would be enough. Adding two, 1", strips in an X or // pattern under the carpet in each footwell won't hurt either.


If you think you can quiet it down more, you can always add more later. But there is no sense in plastering the whole car with $200 of dynamatt if $50 will get you 95% of the benefit.


These guys have the products I'm talking about, but I have no affiliation with them, nor have I purchased from them.




Sorry, I don't have pics, but I've done this on 3 cars so far with outstanding results.


I am getting ready to tackle this project and all I read is people plastering as much stuff as they can on all body panels. Has anyone tried this less is just as good approach? I was going to give it a try. If it does not make a great improvement I guess I could add more. I just don't want to have to tear it appart twice!!! Thanks J

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  • 2 weeks later...

How am I doin'? 3 layers in the front floor pans, 5 layers in the rear floor, 2 layers in the ENTIRE outer skin (doors rear panels and quarters) 2 layers in the inner skins and 7 layers in the trunk.












OHHH and who ever is running Focal +++++9848752934082093842893

Im running MB Quart Q series, IASCA baby!! Thinking about Focal or Dynaudio

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  • 7 months later...
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I'd also like to know about ^^ question.


I was thinking of following the other guide and doing the B-Quiet V-comp install in all four doors, but then also installing the b-quiet ultimate damper, but just doing the center portion of each door (outside panel itself). This would reduce cost for sure and if it's 90% of effectiveness of full coverage, then I'm fine with that.

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I think the 90% effective figure is subjective and untested, but I wouldn't be surprised to see that method permit positive results for you. I put a chevron inside my dented fender, as opposed to wasting sheets of dynamat on full coverage prior to getting the damage repaired, and it lessened vibration I was hearing in the exposed piece. Not sure it's as good as a skin-layer (or like 7, as above), but it will help some.
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I used 50 square feet of B-quiet on my car and tried to go sparingly knowing that I didn't have a whole lot. Took two evenings of peeling and sicking B-Quiet. I did a couple of chevrons on the outer skin of the doors, the closed off all the holes on the inner skin and put 1-3 layers on the whole panel using the knock test method. (If it didn't go THUD, I put on more deadener) Also did up my trunk really well including the spare tire area and then used a high density closed cell foam over the top of the deadener in the trunk.


All in all it was a ton of work for a little more quiet. Don't get me wrong, I would do it again, probably use more deadener though. It is noticeably quieter on the freeway than my dad's LGT, just still not Bentley quiet.


I added a sound system at the same time and it definitely makes that sound better!


Just my experience.

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So, it is hard to say if this mod is worth it?!?!? Some folks say yes, others say too much time!


There are definitely a lot of methods out there with a lot of different products. Did anyone measure their actual db reduction?

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I read a thread about guys measuring the db difference on a rag-top 2002ish vette. They went to town on the car pulling everything out, laying down tons of dynomite and foam on everything floors, doors, firewall, wheel wells. They dropped about 10 db on the project at highway speed on the same stretch of road. That is a lot of noise!


Basically, it does help some (more depending on how in depth and how much product you use). Its quiet a bit of work but nothing at all hard.


Plus it also helps tighten up the sound system! :)

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Hi, I finally got up on the noise in the Legacy, bougth a MB CLK and now it is quiet.


I mounted bitumen mats and noise dampening mats in the whole Legacy, and yes - it sound less, but the factor that generated the most sound - road noise - was never ever effected by the sound deadening methods. From my perspective, it is not worth either the time or the money spent!


Greetings from a happy CLK owner



Edited by petgre
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  • 1 month later...
go to home depot get a roll of ice and water mat for roofing 400sqft or something like that for 100 bucks you can do 6 cars with it and still have some left only downfall is it smells a bit like tar for a few days. i used it in my old blazer running 4 12's and had almost no odd noise rattle outside.
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  • 1 month later...
go to home depot get a roll of ice and water mat for roofing 400sqft or something like that for 100 bucks you can do 6 cars with it and still have some left only downfall is it smells a bit like tar for a few days. i used it in my old blazer running 4 12's and had almost no odd noise rattle outside.


Nvm, been doing more reading and I wouldn't recommend using peel and seal


Are we talking the same thing here?

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