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Foot-wells and firewall (if you can get to it) would be the biggest area's I would hit. Other then that you really only need one layer of MLV. IMHO the firewall, doors, and roof... are the areas you should focus on.
I think you're probably right.
I intend to do some test runs with several mics located very close to those areas to more exactly pin down the noisiest areas, and the frequency/amplitude of that noise at each location.

Unfortunately it seems that the normal Windows OS sound driver doesn't support multiple simultaneous mic inputs. The alternative is to use a multi-microphone interface intended for studio recording (too expensive) or the 3rd-part "ASIO4ALL" driver which evidently can support multiple simultaneous mic inputs with the appropriate recording/mixing software (though I'm still not sure which software actually works).


For best results, should i just do CCF, MLV, MLV? OR should I make a sandwich and do CCF, MLV, CCF, MLV?
I wondered the same thing (Use double alternating foam/MLV layers or one foam/MLV layer that's twice as thick). So I asked Doug at CAE.

While I was waiting for his reply, I found the answer in these two publications:
I ran across a couple of technical papers you might find interesting (if you haven't already read them).
1. Handbook of Noise Control Materials
2. Vehicle Noise Demands Tough Solutions

These excerpts are particularly pertinent::

1. (@ page 3): "For the design of composites, mass layers are typically at weights of 1 and 2 lb/ft2 and the thickness of decoupling layers varies from ¼" to 3". The effective frequency range of these materials varies with the square root of the weight of the mass layer times the thickness of the decoupler (See Fig. 2B).The 1 lb/ft2 material on ¼" decoupler is effective only above 500 Hz, and is generally not satisfactory for noise reduction in boats, except for special applications.The 2 lb/ft2 material on ¼" decoupler moves the effectiveness range down to 350 Hz (this is a construction generally recommended when there is minimum space available for the composite treatment). For a high level of effectiveness the decoupler layer should be 1" or greater and for the highest effectiveness this should be combined with 2 lb/ft2 mass layer, as demonstrated in Fig. 2B. Greater thicknesses of the decoupler increase the bass frequency effectiveness, while heavier mass layers increase effectiveness throughout the entire frequency range."

Here's a chart:


2. (@ page 5): "The double-wall barrier construction acts like a spring-mass system, where the performance of the spring is controlled by its stiffness and thickness. The lower the stiffness, the lower the frequency that sets the double-wall construction into resonance, the point at which it fails to impede sound waves. Similarly, the thicker the spring—in other words, the more deflection it exhibits—the lower the double-wall resonance frequency. In a double-wall barrier system, the decoupling foam acts as the spring. So, the thicker the decoupler and the lower the stiffness, the lower the double-wall resonance frequency."

Both these advise the same thing: for best performance in the hard-to-control lower frequency range, use the most massive (thickest) possible MLV along with the thickest and softest possible decoupler: open-cell foam, which also happens to be a better sound absorber than CCF. (Please refer to the difference between blocking the transmission of sound and absorbing sound.)

High Resilience foam, which has a very fast recovery and bounces back to its original shape faster after compression, is the best foam "spring." The optimal decoupler is a lot less firm (<1psi @ 25% compression) than the closed cell foams (>5psi @ 25% compression) commonly used in aftermarket automotive composite decoupler/barriers. Also keep in mind that MLV is a "limp mass barrier" and its performance is partly related to how limp it is. Being bonded to a layer of foam makes it less limp that MLV by itself. Which brings up the next point: anywhere is is possible to hang the MLV over an open space (such as over the open space of a door), use MLV without any foam behind it, except where it is mounted. That said, any added foam also has the secondary benefit of providing some sound absorption, but a thin layer of CCF doesn't absorb much.

Based on what I've seen on here so far, I expect that some will warn you against using open cell foam. While I understand their concern, you might want to consider that auto manufacturers do not totally avoid use of open cell foam (e.g.: seats). Also, you would have the opportunity to seal all the surfaces when you install it.

Doug at CAE and Don at SDS seemed to think my suggestion of using a much thicker decoupler than the normal CCF was ridculously impractical.
While that may be true under the carpet, the fact is there *should* be that much room behind the dash between the cabin and the firewall and/or front wheelwhells.

Additional references linked in this post.

Also, there is a tremendous amount of related technical info here.

One other thing I can would like to point out: Most "ordinary" passenger cars and trucks have a lot of cavities. The luxury counterparts of those cars often have similar cavities filled with something that is generically called "body foam" (e.g.: 3M Flexible Foam and 3M Rigid Pillar Foam). While these two products are intended for repair (and are ridiculously expensive), there are some more affordable alternatives, FlexFoam-iT! Castable Flexible Urethane Foam (but not the mono-component spray foam like "Great Stuff").
 

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Wow thanks Elvis!! That was very informative. Sounds like a regular layer of CCF/MLV on the floor will work just fine, but I need to double or even triple my ccf and MLV in the footwells and firewall. Based on what you posted, it looks like just doing CCF CCF, MLV MLV would work better than alternating them. Am I correct in assuming this?
 

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the plans I got off of sound deadener showdown site says an additional layer of ccf over the footwell is a good idea.
 

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Wow thanks Elvis!! That was very informative. Sounds like a regular layer of CCF/MLV on the floor will work just fine, but I need to double or even triple my ccf and MLV in the footwells and firewall. Based on what you posted, it looks like just doing CCF CCF, MLV MLV would work better than alternating them. Am I correct in assuming this?
According to the references I cited, thicker materials provide better performance than multiple thinner layers of the same materials, especially at lower frequencies.
This is especially true of the foam layer, which is acting as a spring. One longer spring is preferable to two shorter springs.

As I mentioned, the commonly used neoprene CCF decoupler is much stiffer than optimal.

From page 5 of Vehicle Noise Demands Tough Solutions:
"Air makes the best decoupler, because it lacks stiffness that transmits vibration energy. Unfortunately, air also lacks any matter with which to support a barrier. Foam, however, with its air-filled cells, provides a good second choice."

You want to use the thickest, softest foam available, along with the heaviest MLV.
The two layers do not have to be glued or bonded together.


Without giving any consideration to other factors like water absorption or fire resistance, the optimal foam decoupler is something like this, but with higher resiliency (>50%) if possible.
foamonline sells that foam and others, but doesn't have a good link to refer specifically to it.

FYI: The most common measure of stiffness for foam: "25% ILD (LB)" is the pounds required to compress a 50 square-inch area of the foam by 25% of its thickness. In effect, it is Pounds per Square Inch x 50. A 25% ILD value of 50 is equal to 1 PSI. Most Neoprene CCF is 5 to 7 PSI, which is many times higher than optimal.

It probably won't be long before the guy from second skin chimes in to tell you how wrong I am, and how their products are the best by far. That's the way practically every forum like this works, and that's also why I usually don't bother posting in them. As I mentioned before, I only registered on this site to offer my appreciation for OP TS2F's diligent effort over such a long period of time.

My advice to you is read the technical papers I provided and approach the problem as an engineer would.
Do not be too swayed by testimonials if they are not backed up by product specification & test data.
 

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According to the references I cited, thicker materials provide better performance than multiple thinner layers of the same materials, especially at lower frequencies.

You want to use the thickest, softest foam available, along with the heaviest MLV. The two layers do not have to be glued or bonded together.
GOT IT! Thanks for the help!!!
Another question I guess I might as well ask, How important is it to treat the pillars? Do they need a full treatment of CLD, CCF, and MLV or maybe just some CCF or insulation to fill in the air gaps?
 

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GOT IT! Thanks for the help!!!
Another question I guess I might as well ask, How important is it to treat the pillars? Do they need a full treatment of CLD, CCF, and MLV or maybe just some CCF or insulation to fill in the air gaps?
MLV should cover any large open spaces.

I intend to fill all cavities with an appropriate foam. Then again, I have other design criteria that have to be met, including thermal insulation.

It's difficult to fill most pillar cavities with anything but expanding foam, although you could probably stuff flexible absorber foam into some of them.
When filling body cavities with pour foam, it is important to take steps to avoid trapping water (even in the form of moisture from the air) in the cavity.
I think this is what causes most of the sheet metal corrosion problems that some people have observed when they try to use "Great Stuff" spray foam.

Before buying any products, much less getting started, you might want to take the time to completely read references like these, Noise Blockers vs Noise Absorbers, specifically:

"How to Tell What a Product Is Designed for
When you're looking at a potential soundproofing product, how can you tell whether it is designed for sound blocking or for acoustical room treatment? It's not always obvious from the way the material is advertised. Both types of material may be billed as noise reduction products or sound treatment products, or even as soundproofing products. Here are three ways to tell:
Look at the test data.
If the product specifications include a sound transmission class (STC) number, a transmission loss (TL) curve, or a weighted sound reduction index value, the product was tested as a sound blocking material.
If the specs include a noise reduction coefficient (NRC) or a weighted sound absorption coefficient, the product was tested as a sound absorbing material.
If no test data is available for the product, that means any advertising claims made for the effectiveness of the product are unsupported."


Also, when comparing materials specs, do a cost-benefit analysis.
You might find this stuff to be useful for some of your applications, in areas where you have enough space. There's a reason why OEMs still use fibrous materials for most acoustic insulation, and part of the answer is on the last page of this PDF which shows excellent STC & NRC (although they don't provide specs for the thinner materials) from the same material.

I think this will have to be my last post on this, because I believe am taking the OP's thread too far off his topic (CLD testing).
 

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No trouble at all guys. I started this thread and testing process so I could get my wife's car (which is also our road trip car) as quiet as possible, so any discussion that adds to that is on topic as far as I'm concerned. There will be a dedicated thread for the final results, hopefully not long after we get fully staffed at work.
 

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As long as your door does not fall off due to the extra weight you are fine…lol.

That being said, with CLD, it is a case of dimishining returns after doing only 30% coverage. The 30% goes in the center of the "unreinforced" panels to reduce the panels resonance. ANyting more then that continues to reduce resonance some, but to a MUCH lesser degree, to the point where it is more effective to spend your money elsewhere in the deadening project or sound system.
Thanks for the response. I purchased the pack, so I figure i might as well use it.

I wonder how many sqft "door kits" include in general for deadening packages?
 

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According to the references I cited, thicker materials provide better performance than multiple thinner layers of the same materials, especially at lower frequencies.
This is especially true of the foam layer, which is acting as a spring. One longer spring is preferable to two shorter springs.

As I mentioned, the commonly used neoprene CCF decoupler is much stiffer than optimal.

From page 5 of Vehicle Noise Demands Tough Solutions:
"Air makes the best decoupler, because it lacks stiffness that transmits vibration energy. Unfortunately, air also lacks any matter with which to support a barrier. Foam, however, with its air-filled cells, provides a good second choice."

You want to use the thickest, softest foam available, along with the heaviest MLV.
The two layers do not have to be glued or bonded together.


Without giving any consideration to other factors like water absorption or fire resistance, the optimal foam decoupler is something like this, but with higher resiliency (>50%) if possible.
foamonline sells that foam and others, but doesn't have a good link to refer specifically to it.

FYI: The most common measure of stiffness for foam: "25% ILD (LB)" is the pounds required to compress a 50 square-inch area of the foam by 25% of its thickness. In effect, it is Pounds per Square Inch x 50. A 25% ILD value of 50 is equal to 1 PSI. Most Neoprene CCF is 5 to 7 PSI, which is many times higher than optimal.

It probably won't be long before the guy from second skin chimes in to tell you how wrong I am, and how their products are the best by far. That's the way practically every forum like this works, and that's also why I usually don't bother posting in them. As I mentioned before, I only registered on this site to offer my appreciation for OP TS2F's diligent effort over such a long period of time.

My advice to you is read the technical papers I provided and approach the problem as an engineer would.
Do not be too swayed by testimonials if they are not backed up by product specification & test data.
Before you dismiss the claims made by Second Skin let me say this.
I used their product in my Suburban (see pics posted in this thread many pages back).
Every inch inside the vehicle has been treated with cld, ccf, mlv (the last to as a bonded together product called Luxury Liner Pro).
The only untreated area is the glass.
When sitting inside my vehicle words like "tomb" "sound room" "anechoic" have been used to describe the experience.
If you want it dead quiet, you can't go wrong with their product line.
The stuff is really that good.


Bret
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Before you dismiss the claims made by Second Skin let me say this.... you can't go wrong with their product line...
I'm not disputing that their products perform well for vehicle noise reduction. Other products also perform well. Some others do not.

But I sure do dispute this:
Just an FYI: Spectrum and Spectrum Sludge are a water based toxin free product that once cured will be just as strong, water/mud resistant, and long lasting as any bed liner on the market.
because that last part isn't likely true, given that 2-component bedliners are nearly an order of magnitude (thousands of psi instead of hundreds) tougher/stronger than most most water-borne acrylic exterior coatings for which specs are available.
Is Spectrum strong enough to hold up when used as an undercoating (not as a bedliner)? It may well be, but absent any specs, I have no way to know how it stacks up to the alternatives.

This statement about "just as strong as any bed liner" is what encited what may appear to be skepticism on my part.


...The stuff is really that good.
...which is all the more reason to have claims backed up by specs and performance test data. Practically every mainstream manufacturer has that for things as lowly as caulk. Not having that is like several people who are all acquainted with a driver telling someone who wasn't at the drag race who won and by how much, but nobody seems to know by exactly how much he won, or what the ET or MPH was. ;)

If your decisions are based mainly on testimonials & recommendations, so be it.
As much as possible, I base mine on test data and engineering analysis. A long history of failure analysis proves this is the best way to solve technical problems.

This has really gone on farther than it should have (no surprise there in an online forum) but I think that there's no point in beating this dead horse any more.
 

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I'm not disputing that their products perform well for vehicle noise reduction. Other products also perform well. Some others do not.

But I sure do dispute this:
because that last part isn't likely true, given that 2-component bedliners are nearly an order of magnitude (thousands instead of hundreds) tougher/stronger than most most water-borne acrylic coatings. Is Spectrum strong enough to hold up when used as an undercoating (not as a bedliner)" It may well be, but absent any specs, I have no way to know how it stacks up to the alternatives.

This statement about "just as strong as any bed liner" is what encited what may appear to be skepticism on my part.


...which is all the more reason to have claims backed up by specs and performance test data. Practically every mainstream manufacturer has that for things as lowly as caulk. Not having that is like several people who are all acquainted with a driver telling someone who wasn't at the drag race who won and by how much, but nobody seems to know by exactly how much he won, or what the ET or MPH was. ;)

If your decisions are based mainly on testimonials & recommendations, so be it.
As much as possible, I base mine on test data and engineering analysis. A long history of failure analysis proves this is the best way to solve technical problems.

This has really gone on farther than it should have (no surprise there in an online forum) but I think that there's no point in beating this dead horse any more.
The very fact that we all are participating in this thread tells us that we also are very interested in test data and analysis so you will get no argument from me on this.
I knew from the beginning this thread was going to raise some eyebrows and even get a few manufacturers a little butthurt when the results came out.
I believe I even warned the OP to expect this and not give up on testing.

Now I should point out that I have not used and have no plans on using Spectrum Sludge in my two ongoing builds so I cannot speak for any of the claims made regarding it.
Others will have to speak on that.
All I was trying to drive home with you is not to dismiss SS's product line so quickly which is what I thought you were doing and gave you my personal testimony on why.
I hope that helps.


Bret
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...All I was trying to drive home with you is not to dismiss SS's product line so quickly...
Once again, as I posted on 7/8/2015:
This has really gone on farther than it should have (no surprise there in an online forum) but I think that there's no point in beating this dead horse any more.
...and yet once again I am sucked in...


First of all, please understand that I do not have any axe to grind regarding Second Skin. I neither support them nor would I avoid their products. In fact, since I intend to use a liquid applied dampener, their Spectrum coating is on my candidate list. But CascadeAudioEngineering has a composite loss chart of their comparable liquid-applied dampener, VB-1X, something Second Skin does not have. For all I know, both VB-1X and Spectrum may be the same product from some of the same factories, or maybe there are differences in the performance. Without specs & test results, there's no way to know, really.

And even if companies like Second Skin sold the exact same products as all the others, there is a convenience/practicality from being able to buy a quantity suitable for a single vehicle, rather than having to buy entire rolls. It's like buying carpet from a carpet store, instead of direct from the carpet mill.

Second Skin's products are often recommended by end users, and evidently those who know the people behind Second Skin appreciate that they intend for their products to be among the best on the market, which is expressed here.

But other than that "trust us" letter, here is an example of the specifics that Second Skin tells customers about their products:


I understand that testing costs money that from a certain point of view could be considered to be a waste
(since it does not directly improve the products or sell more of them) and any small business would want to minimize that.

Also, not having full specs like these:


...as provided on these PDFs:
Tuff-Mass Barrier
Vinyl Foam Barrier Composite
Acoustical Absorption Foam
QuietPro Water Resistant Sound & Vibration Absorbing Panel
Polyimide Acoustic Foam
...does (in this respect) make it reasonable to lump Second Skin 's (or any brand name company's) products in with the more generic off-brand products, the quality of which is supposedly inferior.

Of course, just because a company publishes specs or the results of tests (that may have been conducted years ago) doesn't guarantee that the products sold today actually meet those specs.
For example, CascadeAudioEngineering publishes these specs for VB-4, which is MLV bonded to 1/4" thick CCF.

Note that they state a "Thermal Insulation Factor.....R4"
but this cannot be true because closed cell foam of this type is only about R-4 PER INCH thickness.
There is NO insulating foam product on the market that delivers R-4 in only 1/4" thick, period.
In comparison the very best commonly available insulating foam (rigid polyiso Thermax, Tuff-R, etc.) is no more than R-6.5 per inch (aged) or R-7.0 per inch (initial).

CAE's spec sheet states that:
"VB-4 is constructed of a thin, decoupling layer of foam bonded to a dense, 0.100" thick mineral loaded vinyl barrier"
and that the total thickness is 0.250 inches. If that's true, that means the foam must be only 0.150 inches thick, which means it has an R-value of about 0.6 (maybe less). The solid plastc (MLV) layer itself is probably is about R-1 per inch (based on the ratings of most other solid plastics), so if the MLV is 0.100 inches thick, that adds another R-0.1, for a total of about R-0.7, which is far less than the R-4 they claim.

And don't even get me started on how some other companies routinely make wildly exaggerated claims about the R-value (which is resistance to conductive heat transfer) of very thin foam materials, based on the radiant heat rejection capability of a radiant barrier layer!

But other than catching obvious errors like that, given that it takes a specialized testing facility to prove otherwise, potential customers who want more than testimonials have to rely on tests of relative performance, like the OP is conducting. That's why I commend OP TS2F's efforts.
 

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I am new to this thread today. I read the first 3 pages from 2 years ago (4/1/13), then this last page. Is there a link or post # for results of the testing? Did the testing ever happen? I applaud the OP and CLD donors.
 

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Its still on going but if you read through the first 20 pages or so youll see some of the results.. OP says he will make a new thread with the completed results once testing has concluded.
 

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Its still on going but if you read through the first 20 pages or so youll see some of the results.. OP says he will make a new thread with the completed results once testing has concluded.
First 20 pages?? :eek: holy cow. It took me a good bit of time to read thru the first three and last one pages!
Does this forum not have the ability to allow the OP to add updates and current info to the first post, or at least add links or post #'s where info can be found to the first post? Is there a spread sheet with the data on what has been tested to date?

I'll post my bottom line question dilema here, either for answers or pointers/ links to info. Search has not helped me (here or Google).

Can 50Hz - 100Hz sound waves (drone) from mufflers at the back of the car be kept from getting to my ears inside the car by with MLV, etc.?:
1) applying ccf/MLV to just the trunk area
2) ccf/MLV to rest of car floor areas AND the trunk area
3) vibration is not really my issue (no subwoofer), but I am not opposed to including some CLD tiles over 25% of the trunk areas as well as the floor areas if it will benefit my low freq. drone in the cab. My aftermarket mufflers are not that loud at all, but a low frequency sound wave has been created that is annoying as H3ll to the ears. This is a 2015 Mustang V6 convertible. I even went to larger Magnaflow mufflers which made the overall exhaust quieter, but too much drone still remains.
 

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Can 50Hz - 100Hz sound waves (drone) from mufflers at the back of the car be kept from getting to my ears inside the car by with MLV, etc.?:
1) applying ccf/MLV to just the trunk area
2) ccf/MLV to rest of car floor areas AND the trunk area
3) vibration is not really my issue (no subwoofer), but I am not opposed to including some CLD tiles over 25% of the trunk areas as well as the floor areas if it will benefit my low freq. drone in the cab.
Your "Job One" should be figuring out specifically what parts of the car the objectionable sounds (amplitude and frequency) are coming from.

I plan on using at least four or six mics simultaneously. But if you're willing to make multiple passes over the exact same stretch of road, you could get by with fewer mics (but that will never be as consistent either). If you have a Mac laptop, it will be easier, since MacOS supports multiple simultaneous mic inputs. AFAIK, Windows still requires a work-around.

Or you can just do what almost everybody else does: "Play it by ear" and just make the best guesses possible.
 

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Your "Job One" should be figuring out specifically what parts of the car the objectionable sounds (amplitude and frequency) are coming from.

I plan on using at least four or six mics simultaneously. But if you're willing to make multiple passes over the exact same stretch of road, you could get by with fewer mics (but that will never be as consistent either). If you have a Mac laptop, it will be easier, since MacOS supports multiple simultaneous mic inputs. AFAIK, Windows still requires a work-around.

Or you can just do what almost everybody else does: "Play it by ear" and just make the best guesses possible.
Elvis,
Thanks for your input.
I don't have the ability for multiple mic testing. At idle (not at the problemed rpm range under load), I have listened with a stethescope to the midsection stock resonator (under cabin) and the mufflers at the the very back of the car. The lowest res. sound comes the rear 4" of the 21" long mid resonator. The muffler bodies have not quite as low a resonance sound, but low. The exh. tubing all sounds high pitched. Driving in the car at the worst rpm (1750), the sound 'appears' to come from the back of the car. Feeling for vibration with my fingers pressed hard against the carpeted drive line tunnel, I can 'feel' vibration, but more at rpm's above my ending drone range of about 1900, so it may not be related to drone.

Researching MLV and people describing covering for say a well pump or other noisy device, that after covering just three sides of an inclosure, the sound was not reduced much at all, until they completely enclosed the 4th side. This application was likely higher frequencies than I am trying to block. But it make me wonder if even if I was able to cover the entire bottom of the car, does the sound just 'come around' to the cabin even assuming the car has nothing beside it to reflect the sound back? This is the bottom line question for me in this application of sound blocking.
 
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