Interior sound deadening, noise reduction, and thermal insulation

[Tremelune]

I have a stripped down ex-track car that I plan to get as quiet as possible. It will be quite some time before I'm at this phase of my project, but I went down a rabbit hole of research this morning, and I figured I'd put it here for reference.

I see a lot of projects that throw layers of Dynamat over everything or spray in Lizard Skin, which was my plan. I read around a bit, and it seems that Dynamat only solves one of several issues with noise, and the Lizard Skin's main sound-proofing quality is simply mass and the ability to get into cracks and what not. They both do something, but are perhaps not optimal. I'm also not sure I want to spray a bunch of adhesive in the interior, but hell, my carpets are currently glued in, so maybe it's not a big deal.

I read a lot on Don Sambrook's website, wherein he discusses a three-pronged approach to reducing cabin noise. A lot of this is probably overkill (it depends on your goals), but stripping and rust-proofing the interior is the most annoying part of my interior project, so it makes sense for me to investigate noise reduction and thermal insulation while I'm getting in there. :

Welcome to Sound Deadener Showdown | Sound Deadener Showdown


1) CLD - Add a small amount of damping material in the flat spots to reduced the resonance of metal panels.

2) CCF - Add a gasket layer over everything to decouple the barrier from the vibration of the panels.

3) MLV - Add a barrier layer over everything to block the sound with mass.


I used to be a bit of an audio nerd, but I'd only read about the first bit, which is just to add mass to metal to reduce vibrations (via asphalt, Dynamat, Lizard Skin, or bed liner). The rest is similar to principles employed when building recording studios and practice spaces.

This guy is selling stuff, so I looked around a little more, and he seems legit. If nothing else, it seems other entities in the car audio space are adopting a similar approach.

Random praise from an install: Don Sambrook finally silences Jonymac's Catless down pipe

Well-worded dissection of the performance of FatMat, asphalt, and other cheap roofer tiles: Thoughts On Fatmat - Product Reviews - Post a review on a product you have first hand, personal experience with. - SMD Forum

Another report from a Tesla owner: Sound deadening work begins next week: will report before and after data

In terms of thermal insulation, that seems to be the spray stuff, mostly. Not sure how that would factor in, if at all. It seems to only make sense for air-conditioned cars, and that's a project that is way way in the future...but while I'm in there...

[nineball]

don is a good guy and his products are top notch. i have used them in many installs.

if you are after that "luxury car" quiet ride you do need the 3 step approach:

1. CLD - don's tiles, dynamat, damplifier, etc. these convert vibrations into low-level heat which is dissipated via the aluminum layer. you only need 25-40% coverage on flat panels, any more is a waste of time, money and product. several companies also make liquid-based versions of these but personally i have found it's much easier to work with something you can cut to size as needed. as you have found you want to stay away from anything asphalt-based in favor of a butyl-based product.

2. de-coupler - typically it is closed cell foam, sort of like a yoga mat or camping pad. this needs 100% coverage, seams taped.

3. MLV - mass loaded vinyl. this is where the weight comes in as you typically want a 1lb/sqft product and it requires 100% coverage, again taping the seams.


for heat insulation there are a few choices out there. second skin (who makes damplifier) has a couple products to choose from depending on how extreme you want to go. honestly i don't think it is needed in a 911 unless you live in a very warm climate, drive it daily and have no ac. doing the 3 steps inside the cabin and a quality mat inside the engine bay should suffice for 90% of the people.

[Tremelune]

Is this 3-step process known in the audio/interior industry? Like, is there a common term? Every build I've ever seen has, at most, simply covered everything in Dynamatish material and called it a day. I'd like to find out what benefits this 3-step process has over older methods to see if they are tried-and-true or merely dated.

I also hate doing interior work myself. I'm looking for someone to strip my interior and give it a serious sound-deadening treatment, but I am specifically looking for someone who is more knowledgeable and better-researched in the field of acoustic management than myself, not someone whose credentials top out at knowing how to install a subwoofer.

[wayner]

I added dynomat like many of the builds here. Waste of time.

Only add a little bit to panels that vibrate in order to dampen them.

I added closed cell foam, that cut noise in half at least (subjectively particularly compared to dynomat)
Now that I have experimented with those I now plan to add the third layer this summer, attached using velcro fasteners so that I can pull it up if I need in the future.

Glue down the velcro to the metal, cut a hole to allow access to the velcro in the middle layer.
Attach the top layer to the velcro patch.
That way if water gets in you can lift it all out.

Coincidentally, when I went mouse hunting in my aunts honda, it had the three layer system from the factory.

[nineball]

Originally Posted by Tremelune

Is this 3-step process known in the audio/interior industry? Like, is there a common term? Every build I've ever seen has, at most, simply covered everything in Dynamatish material and called it a day. I'd like to find out what benefits this 3-step process has over older methods to see if they are tried-and-true or merely dated.

I also hate doing interior work myself. I'm looking for someone to strip my interior and give it a serious sound-deadening treatment, but I am specifically looking for someone who is more knowledgeable and better-researched in the field of acoustic management than myself, not someone whose credentials top out at knowing how to install a subwoofer.

the "3 step process" is an aftermarket thing. auto makers are concerned with weight and cost more so than the end results. add on even $1 per car made and the figure is staggering.

1. apply a cld (constrained layer damper). this is what dynamat xtreme, sds tiles and second skin damplifier / damplifier pro are: a butyl-based rubber with a layer of adhesive on one side and a layer of aluminum on the other. the adhesive side is applied directly to the metal panel, the butyl converts vibrations into low level heat which is then dissipated by the aluminum. you only need 25-40% coverage on large flat panels for this to be 100% effective. there is no need to do 100% coverage as you are just wasting time, effort and product (money).

2. apply a ccf (closed-cell foam) decoupler. most people use ensolite, or a similar closed-cell foam product. thickness varies but a minimum is 1/8", up to 1/4" will work as well. this acts as a decoupler between the cld and mlv and also serves to block some of the spectrum of sound. some come with adhesive applied already but if not something like 3m super90 spray adhesive will do the trick. this needs 100% coverage.

3. the last step, and the one that actually blocks (or repels) the sound is mlv or mass loaded vinyl. the optimal solution for most car applications should weigh approx. 1lb/foot, and this needs 100% coverage to be effective. you also need to seal up any seams as noise (like water) will find the path of least resistance. overlapping the mlv and sealing it with a contact cement-type glue is the best method but you can also use a heavy duty tape.

ps> applying steps 1 and 2 to the inside of the outer skin and inside of the inner skin of the doors will greatly improve your audio output as well. the cld helps with vibrations caused by the speaker and the ccf absorbs the backwaves of the speaker.

you can also browse FAQ | Sound Deadener Showdown and read up.


if you are going to pay someone else to do it don't expect a cheap bill. this is a very labor intensive project considering you need to gut the entire car, install everything and then put it all back. i've done more than my fair share of cars and it still took me about 4-5 weekends to get the job done, long hours each day.

[Tremelune]

Have you ever done an old 911? I'm curious to know what weirdness might be there, what with the strange frunk and what not...I'm happy to work on my car, but stripping interiors is tedious, tiring work that I'm happy to pay for. The hard part is finding someone who will really do it right.

[nineball]

it seems like everyone else has done it, so why not me... (interior)

there really isn't anything to do to the frunk.

[Tremelune]

Ha, oh man—that was the thread that ultimately convinced me to pay someone else to do it!

[nineball]

it's not that hard to do, just labor intensive. plus you get that great feeling of doing something yourself

[nilknarf]

When I did my interior, I painted in a thick layer of Lizard Skin, followed by two full layers of an eBay-sourced dynamat-like material (adhesive-backed rubber/aluminum sandwich construction) over the entire interior before installing an RS carpet kit... I don't know how it would have sounded without my measures, but like wayner, I've been very disappointed with my results- my car is much noisier than I hoped it would be (mostly engine noise that gets in the way of conversation).

[Pstallo]

I'm currently stripping out my interior and planning on installing Dynamite before new carpet. This is making me think that I'll need another layer or two of sound deadening before I reassemble everything.

There's no serious weirdness in the removal of the interior. It's actually surprisingly easy. The trick is scrubbing out all the gunk so the deadening material will adhere. I've been working on that for two days.

[nilknarf]

Originally Posted by Pstallo

I'm currently stripping out my interior and planning on installing Dynamite before new carpet. This is making me think that I'll need another layer or two of sound deadening before I reassemble everything...

Wise man! You might also check out B-Quiet | Porsche 911E- I seem to recall someone else on the boards using their products to good effect- money was a bit tighter when I did my interior so I went the cheaper (and in my opinion, less effective) route...

Curt

[nineball]

Originally Posted by nilknarf

When I did my interior, I painted in a thick layer of Lizard Skin, followed by two full layers of an eBay-sourced dynamat-like material (adhesive-backed rubber/aluminum sandwich construction) over the entire interior before installing an RS carpet kit... I don't know how it would have sounded without my measures, but like wayner, I've been very disappointed with my results- my car is much noisier than I hoped it would be (mostly engine noise that gets in the way of conversation).

sounds about right. i personally have never been a fan of the spray/paint-on versions. in this case you added a cld, then put more cld on top of that then more cld on top of that. in the end all you did was add mass to your panels and change their resonant frequency.

Originally Posted by Pstallo

I'm currently stripping out my interior and planning on installing Dynamite before new carpet. This is making me think that I'll need another layer or two of sound deadening before I reassemble everything.

There's no serious weirdness in the removal of the interior. It's actually surprisingly easy. The trick is scrubbing out all the gunk so the deadening material will adhere. I've been working on that for two days.

not sure if i would install dynamite in my 911 but to each his own

[Pstallo]

durn spellcheck! Actually, maybe dynamite would be a better option to get all this glue gunk off! I think I am about to switch from acetone to Citristrip, though. It has to be a more pleasant alternative.

[tirwin]

When I did my interior I used a layer of Dynamat (or Damplifier? I can't remember), then a layer of 1/4" closed cell foam and finally a layer of MLV.

I just put in the Ultimate sound pad from Appbiz in the engine bay. I'll be interested to see how that changes things.

At the end of the day, it's a sports car not a luxury sedan. One of the benefits of the 911 is that if someone calls me and I'm about to get in the car I just say "gotta go. It's about to be too loud to talk."

[david.avrahami@]

3 years ago I removed the whole interior of my 87 Carrera and recovered it all with 2 layers of : 1. B-QUIET product to mainly eliminate vibrations (B QUIET ULTIMATE)
2. MLV (see below)
3. blanket for the inside of the motor compartment fire wall - sold by pelican

I have a free flow cat and muffler that produce great music to my ears BUT are much more subdued NOW.



MASS LOADED VINYL

What is Mass Loaded Vinyl?


MLV

MLV or Mass Loaded Vinyl is a sound barrier blocking material known as a “Limp Mass Barrier.”

The material is comprised of two principle ingredients: vinyl — to give the MLV flexibility (the so called limpness) and, a naturally occurring, high mass element. Often Barium Sulfate is used due to its unique properties – it is non-toxic and has a high relative density. This latter attribute of high density is what makes Mass Loaded Vinyl so effective in blocking sound.

[TheSt|G]

I've used dynamat a number of times on past projects(generally shutting up domestic and JDM cars), and have always been very pleased with the results. Perhaps those who have been having poor results used their cheap stuff?

On the 911 I plan on doing a combination of QuietRide and dynamat coverage.

[wayner]

Dynomat doesn't absorb anything It just dampens panel vibration. The wrong stuff to use over the entire surface in my opinion. Weight with not much value.

If on the other hand you have a strut tower on a civic that goes"bong" over bumps, or a floor pan that resonates, small pieces of dynomat help with that , but you don't; need full coverage. Save the weight and effort for the proper sound materials

[Tremelune]

If you guys are interested in sound deadening, you should really really read the first link in this thread:

Welcome to Sound Deadener Showdown | Sound Deadener Showdown

[1-ev.com]

My method...
if i am running an Electric motor - its Very quiet and FAST...

when I am running 2.8L with pipes - its is Very Loud... so I'll swap Motors as needed...