# Reducing noise floor and cabin din in the car.



## tspence73 (Oct 14, 2008)

Hey all,

In my future plans for my car. Reducing driving noise is a big factor in getting the highest quality from my system. Here are the things I've come up with to help reduce my in-cabin noise:

1. Butyl rubber damper on the entire car interior, including the roof to calm metal resonance and vibration. I have chosen Damplifier and Raamat as the products I will use to accomplish this.

2. Possible second material foam or other damping/proofing material on top of the butyl rubber. (Taking suggestions on the proper material to go over the butyl rubber damper).

3. Sludge for the wheel wells of the car. (I need some product advice on this as well).

4. I will be doing 17" wheel eventually on my Sentra, so I can look at my car and get a woody.  But there is another purpose. Tires. What tires will most likely give me the quietest ride and lower the road noise?

Suggestions are appreciated.


----------



## Rudeboy (Oct 16, 2005)

You really need to look at a barrier to use on top of the vibration damper to block noise.


----------



## tspence73 (Oct 14, 2008)

Rudeboy said:


> You really need to look at a barrier to use on top of the vibration damper to block noise.


That's the question on step 2 above. If you have a suggestion or special product you prefer, please list it.


----------



## Mooble (Oct 21, 2007)

tspence73 said:


> That's the question on step 2 above. If you have a suggestion or special product you prefer, please list it.


Thick and heavy, that's the key. Ideally, you need to glue a dense barrier on top of foam. You want a foam that is rigid enough that it won't compress and thus lose effectiveness. You can see my trials and tribulations with various methods in the build section. If you are only trying to kill road noise, you probably don't need something as dense as lead. A 2mm rubber barrier worked for me. In my experience, however, killing something like aftermarket exhaust noise requires lead or a very heavy vinyl barrier. Nothing else seems to be effective enough.

Once you've blocked as much noise as you can, you then need an absorber. Recycled cotton batting does this very well.


----------



## Rudeboy (Oct 16, 2005)

Mooble said:


> Thick and heavy, that's the key. Ideally, you need to glue a dense barrier on top of foam. You want a foam that is rigid enough that it won't compress and thus lose effectiveness. You can see my trials and tribulations with various methods in the build section. If you are only trying to kill road noise, you probably don't need something as dense as lead. A 2mm rubber barrier worked for me. In my experience, however, killing something like aftermarket exhaust noise requires lead or a very heavy vinyl barrier. Nothing else seems to be effective enough.
> 
> Once you've blocked as much noise as you can, you then need an absorber. Recycled cotton batting does this very well.


Heavy is the key - if you have a sufficiently dense material, thickness doesn't matter. Lead is ideal, but mass loaded vinyl is easier to get and much cheaper. You could also use aluminum or copper, but 1 lb/ft² seems to be the sweet spot. You also want a resilient foam to lift the barrier off the sheet metal - the more air the better, but as mentioned, you don't want it to compress. You don't need to glue any of this down to horizontal surfaces, particularly if the carpet will hold it in place. Second Skin Luxury Liner Pro and Cascade VB 4.5 are very nice products that already have the barrier and foam sandwiched together. You can also find bulk sourcing intended for construction, but you have to be careful about the foam since most is OC.

Absorption is tricky in a car, especially in tight spaces like on the floor and in the doors. Since you need a material that is at least as thick as 1/4 the wavelength you want to absorb, you are pretty much limited to high frequencies. To give you an idea, to absorb 250Hz, you need a material at least 13.5 inches thick.


----------



## Mooble (Oct 21, 2007)

MLV is a little cheaper. I saw a 4x8 sheet of MLV for $125 and 4x8 lead sheets for $180. Both were 2 lbs sq/ft. The lead is only 1/32" thick whereas the MLV was a full 1/4". I think the lead would be easier to install because it retains its shape and it's thin. I don't know how easily you can bend 1/4" vinyl, but methinks it's not easy.


----------



## braves6117 (Feb 13, 2008)

How do you plan to mount MLV on your cieling? 

And if you don't plan to, what will you use on top of your damplifier?

And a good source for MLV,

http://www.mcmaster.com/

Search mass loaded vinyl


----------



## Mooble (Oct 21, 2007)

braves6117 said:


> How do you plan to mount MLV on your ceiling?



I don't think you need it on the ceiling. You aren't getting low frequency noise from on high. A layer of cotton batting should be sufficient to stop noise from above. You need the heavy stuff for the floor where all the low frequency rumbles come from.


----------



## Rudeboy (Oct 16, 2005)

Mooble said:


> I don't think you need it on the ceiling. You aren't getting low frequency noise from on high. A layer of cotton batting should be sufficient to stop noise from above. You need the heavy stuff for the floor where all the low frequency rumbles come from.


You do want the vibration damper on the ceiling though - reduces wind noise and makes a huge difference in the rain


----------



## bobduch (Jul 22, 2005)

My 2 cents FWIW:

1) Yes, the whole car including roof with deadener. That said you may not need to do the floor. Why? Think about it. Deadener is used to stop metal (or plastic) from vibrating. Most of the time floors are thick or heavy enough that they don't vibrate. Rap on the floor with your knuckle. Does it make a sound similar to when you do that to your door? Or is it more of a thud. If more of a thud deadener won't do much. (Of course if your into extreme overkill, go wild.) Try to get it up over the firewall. Hard to do but that can help alot. In my vehicle I also got it over the wheel wells as they were not as solid as the floor. And I did my roof.

2) I used Scosche AMT250 barrier on the floors and over the wheel wells and as far up the firewall as I could. It is a heavy rubber and foam product. It is a barrier as apposed to a deadener.

3) Again, I used the barrier over the inside wheel wells. Then I took the wheels off and cleaned the outside wheel wells with a power washer. Then sprayed on several thin coats of rubberized undercoating from PEP Boys or Autozone, forget which.

4) For low tire noise go to tirerack.com and search. They rate tires including noise. Never tried them but Goodyear makes a tire with an extra belt of something that they claim makes the tire quieter. I would expect a performance tradeoff. Just depends on what is most important to you. I always notice how much quieter new tires are. Thick tread is hard to beat.
Cheers!


----------



## tspence73 (Oct 14, 2008)

bobduch said:


> My 2 cents FWIW:
> 
> 1) Yes, the whole car including roof with deadener. That said you may not need to do the floor. Why? Think about it. Deadener is used to stop metal (or plastic) from vibrating. Most of the time floors are thick or heavy enough that they don't vibrate. Rap on the floor with your knuckle. Does it make a sound similar to when you do that to your door? Or is it more of a thud. If more of a thud deadener won't do much. (Of course if your into extreme overkill, go wild.) Try to get it up over the firewall. Hard to do but that can help alot. In my vehicle I also got it over the wheel wells as they were not as solid as the floor. And I did my roof.
> 
> ...


Cool thanks! Now we need more answers like this guy's! Those are the kinds of answers and info that when enough people contribute, everyone benefits and can plan projects with good options and ideas and answers.


----------



## bobduch (Jul 22, 2005)

Your welcome. I also used Scosche AMT750, high temperature 3/4" inch thick foam made to line the underside of your hood. Keep engine noise from going through the hood and back through the windshield. I also lined the engine side of the firewall with it.
If you want any Scosche stuff I can get it for you for about half retail. I actually have 3+ sheets (24"x27") of the AMT250 and a new box of AMT750 (2 sheets 24"x27") left from my last project.


----------



## tspence73 (Oct 14, 2008)

bobduch said:


> Your welcome. I also used Scosche AMT750, high temperature 3/4" inch thick foam made to line the underside of your hood. Keep engine noise from going through the hood and back through the windshield. I also lined the engine side of the firewall with it.
> If you want any Scosche stuff I can get it for you for about half retail. I actually have 3+ sheets (24"x27") of the AMT250 and a new box of AMT750 (2 sheets 24"x27") left from my last project.


Do you have pictures of how this stuff is installed? I'm a real novice at the advanced projects but with a few basic pictures and easy instructions I think I can do it.


----------



## bobduch (Jul 22, 2005)

I don't think I do. If you search you'll probably find plenty of pics from others. Look for csuflyboy. We used the AMT250 on his Audi's floor and I know he had pics (he competes (well) and so takes pics of everything). If ECA was still up I know they were on there. But check here.
It is very easy. The trick is getting the carpet and some trim pieces out, and then getting them back where they belong w/o losing pieces. The hard part is getting up the firewall.


----------



## What? (Jun 5, 2008)

I recommend Michelin for quiet tires. You could also go to Lexus, Benz, etc dealerships and see what they use from the factory on the high end sedans.


----------



## tspence73 (Oct 14, 2008)

Remember guys,

This is all long term (like a 1-year plan). I don't know how much of a budget I will have after my front door pods and likely trunk damping. I will try to snatch some extra overtime here and there and scrimp and scrape for the extra dough.

Today, I did my preliminary parking lot SPL test with my meter. I got an unbelievably high 72-75db SPL! I wasn't even driving faster than 18-20mph!  I had no idea cars were so noisy. I have a bad feeling this will get up to the 80's at 45-50mph. This will be an uphill battle for every lost db of low-level sound!  Can I ever hope to have like a 67db SPL average at 45mph on a good road?

Does anyone have a simple SPL meter they can test in their 'quiet' car and tell me what SPL they get at 45mph on a good road?


----------



## sqshoestring (Jun 19, 2007)

Look up tests on car and driver or some other auto mag, some of them do show db levels at idle and 60mph or something. Not sure on cost but you can do more outside the car too, you can spray something like stone/gravel guard inside the wheel wells and floor areas. Just stay away from brake likes or moving/hot parts and exhaust/etc. or see if a bodyshop will do it for you as it may be hard to get it thick enough with spraycans. Then you can spray the asphalt stuff on. Before they used plastic wheel wells they sprayed the metal with some thick rubber stuff. I'd recommend you take those loose and spray the metal under the plastic wheel wells also. Alternately you could have bedliner put in the wheel wells or try it yourself. Anyway, since that is likely largest source of noise (tires) it may help and you can still put whatever inside the car. I used to do the above with my cars, well ones that needed it. Another budjet way is if you have access to junk cars or junkyards you can take the insulation out of another car and put it in yours, under the carpet. Just cut to fit, but some cars just have molded carpet and no removable sound insulation. Here they have a DIY junkyard, it is great you can just tear through cars until you find what you want. I'm too busy to do that stuff anymore but some of the factory stuff is pretty high quality. Cadillac used to use some nice recycled cotton looking stuff. Also check around the steering column at firewall, some cars leak noise there but make sure nothing can interfere with the steering of course, could be very dangerous.


----------



## CobraVin (Jul 31, 2007)

i took readings in the vette with a radio shack digital db meter as well as my m audio mic/laptop setup at different speeds as well as idle before my install, im finishing it up so i will take after tests to see how much of a difference it made

i used sound deadener and mlv(1/4" closed cell with 1/8" mlv already attached and sealed the seams with lead tape, i did the entire cockpit,somewhat up the firewall, rear hatch area,the doors, i removed the rear inner fender wells and covered them with mlv as well, after i get the interior buttoned up ill take tests again, then im going to dynamat extreme under the hood and use some mlv there as well as what i can in the front fender wells(theres not much i can do there)

im going to cover the inside removable glass top with something, not sure what right now, mlv would be to heavy there. plus i wouldnt want it falling on my head while im on the highway if it lets loose, i like the removable top but i hate the sun always in my eyes, so ill kill two birds with one stone there

ill post the results


----------



## gijoe (Mar 25, 2008)

There is a diffident trade-off for tires. Usually when you up the wheel size you make the profile of the tire lower, this means stiffer, which is great in the corners, but not so great for noise. A good all season or touring tire will be the quietest. As mentioned above, check out tirerack. I have a set of Michelin Harmony's on my Subaru and love them. They are nice and quiet they do well in all weather and they don't look too bad.


----------



## tspence73 (Oct 14, 2008)

gijoe said:


> There is a diffident trade-off for tires. Usually when you up the wheel size you make the profile of the tire lower, this means stiffer, which is great in the corners, but not so great for noise. A good all season or touring tire will be the quietest. As mentioned above, check out tirerack. I have a set of Michelin Harmony's on my Subaru and love them. They are nice and quiet they do well in all weather and they don't look too bad.


So, do you think a 15" wheel's tire is quieter than a 17" wheel's tire?


----------



## bobduch (Jul 22, 2005)

Is your meter measuring with "A" weighting or "C" weighting. Different scales-with different readings.
In my van I get as high as 74db at 70 mph on concrete pavement and as low as 64db on smooth tar. (I love fresh pavement!)
If your car is that loud you'll get very noticable improvements.
And yes, you take off plastic wheel well trim before spraying on undercoating.
Don't worry about what Lexus etc. use. My 5 series has high performance tires (supposedly noisy) and the car is quiet. Very quiet. Those cars are quiet because of what is engineered into the car for sound proofing, not the tires they use.


----------



## AAAAAAA (Oct 5, 2007)

Paying attention as I am having troubles making my SUV quieter.


----------



## tspence73 (Oct 14, 2008)

bobduch said:


> Your welcome. I also used Scosche AMT750, high temperature 3/4" inch thick foam made to line the underside of your hood. Keep engine noise from going through the hood and back through the windshield. I also lined the engine side of the firewall with it.
> If you want any Scosche stuff I can get it for you for about half retail. I actually have 3+ sheets (24"x27") of the AMT250 and a new box of AMT750 (2 sheets 24"x27") left from my last project.


Hey. Another question. Does this stuff go over/work with the metal damper products like Second Skin or even the Quiet Car paint-on damper?


----------



## guitarsail (Oct 12, 2007)

So all this talk about noise reduction..btw my wallet hates you guys...all this talk about noise reduction...i've got myself a couple layers of damppro/dynamat extreme, sludge, layer of OKPro...now the question....I've got some MLV, enough to cover the interior floor with...should I put that strait onto the OKPro or get another layer of foam are some sort of decoupler in between it then the MLV? Would a nice thick layer of recycled cotton do the trick for a absorber slash decoupler....I have enough recycled cotton to also do a layer on top of the MLV before carpet as well...I was good on my plan right up to the MLV then I got a little lost as to decouple from the OKPro, or not. sorry for the noob question....


----------



## tspence73 (Oct 14, 2008)

Hey,

Any opinions on Quiet Car liquid paint-on damper? The company claims better damping and sound proofing than any butyl mat damper by more than 2 times. Is this true? Anyone have an opinion?


----------



## Rudeboy (Oct 16, 2005)

tspence73 said:


> Hey,
> 
> Any opinions on Quiet Car liquid paint-on damper? The company claims better damping and sound proofing than any butyl mat damper by more than 2 times. Is this true? Anyone have an opinion?


This should tell you all you need to know:


QuietCar Web site said:


> QuietCar, on average, is less expensive, lighter, and takes less time to apply than mats. With QuietCar, significant noise reduction can be achieved without removing the seats and carpeting. Just and undercoat and wheel wells can have a significant impact. *Moreover, QuietCar absorbs the actual noise and vibrations across a wide frequency range, rather than just mask it or try to shift the frequencies. QuietCar literally absorbs the energy, and this is a key difference between QuietCar and other products. With QuietCar, even if you don’t get every nook and cranny, vibration is absorbed and dissipated nevertheless.* So QuietCar is easy to use.


Pure marketing BS. "rather than just mask it" - what the hell does that even mean outside of active damping systems. Also notice that even though the link claims to be taking you to a comparison with Dynamat, this illustration








compares it to asphalt mat - which I'm finding to be less than 1/4 as effective as butyl/aluminum foil. Yeah, yea, maybe they are referring to Dynamat Original, but they are certainly letting the ambiguity work in their favor. The implication that mats require full coverage is nonsense. Liquids are almost certainly going to be at least somewhat less effective than mats because they don't employ a constraining layer. In my experience (which doesn't include QC), they range from slightly less effective to significantly less effective. 

You have to ignore claims like this. At one point, everyone was claiming their liquid was "lighter, better, cheaper" - until people started doing some simple arithmetic. At recommended thicknesses, the liquids weighed the same as mats and no testing has ever shown them to be superior. As far as being easier - yeah, if the car is alreay stripped and masked and you have a spray booth. Otherwise, applied with a brush, it takes much longer to cover a surface with liquids since you need to apply several coats and allow each to dry. eDead and FatMat have also claimed to be "better than Dynamat" and neither are even close to being as good.

Just noticed - what the hell are they charting on the y-axis? Damping is described by acoustic loss factor. 1.00 is perfect. Their chart goes to 9.00.


----------



## sqshoestring (Jun 19, 2007)

That is likely the stuff I've seen on cars factory, its a thick rubber type stuff sprayed on. It looks like spray bedliner material but is very rough so must have been sprayed thick. Most road noise is from tires, so if you did what they say and blast wells/etc around the tires you will cut a lot of noise and can also apply other things inside the car. Is likely the rubber type stuff dampens typical frequency of tire/road sound, seems that way in my experience. 

How well it works compared to other things is hard to say, but I do think exterior materials are more effective from the standpoint that _they protect from noise rather than only dampen the noise already there_. Once the noise gets to the steel it travels.

From what I read it is best to have layers, the sound has a harder time moving through layers of different material. That is why lead layered works so well. Or it could be different layers hit different frequency too, that seems pretty obvious.


----------



## bobduch (Jul 22, 2005)

I have found the mats better than the liquids.
The two best I've used are Dynamat Extreme and Scosche AMT60. I find them to be so close that in a blind test I don't think I could tell one from the other except I think the Scosche may stick better.
I get Scosche at dealer cost (and will get it for anyone here at dealer cost too-just as a gesture to help out my fellow crazies). Last time I ordered a box (8 sheets 24"x27") of AMT60 it was $120. I assume that has not changed. Retail is $250, same as Dyn Extreme last I looked.


----------



## tspence73 (Oct 14, 2008)

bobduch said:


> I have found the mats better than the liquids.
> The two best I've used are Dynamat Extreme and Scosche AMT60. I find them to be so close that in a blind test I don't think I could tell one from the other except I think the Scosche may stick better.
> I get Scosche at dealer cost (and will get it for anyone here at dealer cost too-just as a gesture to help out my fellow crazies). Last time I ordered a box (8 sheets 24"x27") of AMT60 it was $120. I assume that has not changed. Retail is $250, same as Dyn Extreme last I looked.


24"x27" is barely bigger than 2 square feet. 8 sheets at most would be like 18 square feet? For $120? Isn't Raamat 62.5 square feet for $130 shipped? What would be the difference between the two? I will be looking into doing my car hood with some kind of damper that can take high heat and stay stuck.


----------



## snaimpally (Mar 5, 2008)

Several DIYMA folks helped me deaden my car a few months ago. It worked well for me so here is what I suggest:
- 2 layers of Damplifier or similar on all metal surfaces - doors, ceiling, floor etc.
- Closed cell foam (volara or ensolite) glued on top of the Damplifier. I used 3/8" volara (from thefoamfactory.com) on the ceiling and doors. 1/8" ensolite on the floors.

I put a coat of Spectrum on most surfaces before adding the foam but you could probably skip that. My roof is so quiet that when it rains all I hear is the splat of drops hitting my windshield. Outside noise is significantly reduced. 

If I had to do it over again, I might add MLV to the mix.


----------



## bobduch (Jul 22, 2005)

It's actually 36 sq ft. And I like it better than the other. It was worth the extra $ to me. And I'll leave it at that.


----------



## Jimi77 (Jul 4, 2005)

bobduch said:


> I have found the mats better than the liquids.
> The two best I've used are Dynamat Extreme and Scosche AMT60. I find them to be so close that in a blind test I don't think I could tell one from the other except I think the Scosche may stick better.
> I get Scosche at dealer cost (and will get it for anyone here at dealer cost too-just as a gesture to help out my fellow crazies). Last time I ordered a box (8 sheets 24"x27") of AMT60 it was $120. I assume that has not changed. Retail is $250, same as Dyn Extreme last I looked.


AMT60 - is that stuff you showed me? Foam with a vinyl barrier?


----------



## tspence73 (Oct 14, 2008)

bobduch said:


> It's actually 36 sq ft. And I like it better than the other. It was worth the extra $ to me. And I'll leave it at that.


I'm looking eventually for something effective that can damp external car panels and the engine hood. Can this stuff work good to damp the engine hood.


----------



## drocpsu (May 3, 2005)

am i allowed to push the "you should have searched first" button here?


----------



## Rudeboy (Oct 16, 2005)

drocpsu said:


> am i allowed to push the "you should have searched first" button here?


I was thinking the same thing.


----------



## bretti_kivi (Dec 3, 2007)

hell, let's make it easy: 

http://www.diymobileaudio.com/forum/showthread.php?t=33449
http://www.diymobileaudio.com/forum/showthread.php?t=48995

to the OP: *go read*

Bret - who is going to go press "YSHSF" now.


----------



## bobduch (Jul 22, 2005)

James, the AMT060 is dampener-butyl and foil-like Dynamat Extreme, but I like it better.
Your thinking of the AMT250, which is the foam and rubber barrier.
The AMT750 is 3/4" high temp foam for use on the hood and firewall.

I think you could use the 060 on the hood and then 750 over it to keep it from getting too warm. I wouldn't bother though. Just use the foam. Your not getting any hood vibration that you can hear in the car.


----------



## tspence73 (Oct 14, 2008)

Yeah, after doing some preliminary test tones, even my old amp is strong enough to show that my interior cabin just has so many resonances from the plastic panels throughout the car, including the front dash. Frequencies from 70Hz - 150Hz cause various plastics to resonate in the car. I don't normally hear them during music playback, but they are there when the right tone is played loudly. It's like trying to plug a thousand hole in a leaky boat. Just when you think one thing is taken care of, another bunch pop up.  Is there any treatment for plastic panels other than to put foam between the buzzing plastic? What about when you can't put foam between a buzzing plastic panel? What about when it's a visible section where two plastic panels meet and you can't get anything between them?


----------



## Jimi77 (Jul 4, 2005)

tspence73 said:


> Yeah, after doing some preliminary test tones, even my old amp is strong enough to show that my interior cabin just has so many resonances from the plastic panels throughout the car, including the front dash. Frequencies from 70Hz - 150Hz cause various plastics to resonate in the car. I don't normally hear them during music playback, but they are there when the right tone is played loudly. It's like trying to plug a thousand hole in a leaky boat. Just when you think one thing is taken care of, another bunch pop up.  Is there any treatment for plastic panels other than to put foam between the buzzing plastic? What about when you can't put foam between a buzzing plastic panel? What about when it's a visible section where two plastic panels meet and you can't get anything between them?


Get some butyl camping sheets and rip out all your panels and damp them that way. I've had mixed results doing this and have actually made the problem worse by lowering the frequency the panel vibrated at. 

You can jam folded up paper between panel seams to stop them from vibrating against each other.


----------



## tspence73 (Oct 14, 2008)

Jimi77 said:


> Get some butyl camping sheets and rip out all your panels and damp them that way. I've had mixed results doing this and have actually made the problem worse by lowering the frequency the panel vibrated at.
> 
> You can jam folded up paper between panel seams to stop them from vibrating against each other.


There are even vibrations at 110Hz that I swear are coming from my A/C vents. Like that tone is a perfect harmonizer for that plastic. It really makes me understand just how difficult to impossible it is to take a car and make it into a rolling listening room.


----------



## CobraVin (Jul 31, 2007)

tspence73 said:


> Is there any treatment for plastic panels other than to put foam between the buzzing plastic? What about when you can't put foam between a buzzing plastic panel? What about when it's a visible section where two plastic panels meet and you can't get anything between them?


yes, silicone


----------



## tspence73 (Oct 14, 2008)

CobraVin said:


> yes, silicone


You mean, like the clear goop? I actually have some of that!  I won't actually have to spend money?


----------



## sqshoestring (Jun 19, 2007)

I think I suggested that in the 6x9 thread for your door panels. You can drill/cut a hole in the back and squirt caulk tube of silicone right in to take care of vibration. They have it on sale for a couple bucks a tube all the time around here, I'd recommend only 100% silicone not the half breed stuff though in some things latex will work too. The silicone sticks to stuff better, if you put a glob inside panels every so many inches it will glue it right together and since it is like rubber it absorbs vibration. It does stink for a while, the latex based does not but will rust bare steel until its dry. If you can clean the plastic where you use it, some plastic still has a mold release agent on it. Something like lighter fluid or mineral spirits works well if you wipe it off all the way, or maybe a soap/foam cleaner would too.


----------



## supernova7 (Dec 30, 2009)

**SUPERBUMP** for random old thread and no apparent reason


----------

