Current recommendations for sound deadening and insulation

[AU Doc]

what's the current guidance on sound deadening and insulation for a protouring car? In the process of relocating my battery to my trunk, I ended up tearing out my interior and coating my floor plans, and I figure I might as well put in something to help keep it quiet and cool.

Not it sure if it matters, but this is a 1969 camaro.

Thanks for the help!

[chuckd71]

I'm sure you'll get a thousand different answers here but car audio forums will have lots of better information. Some of those guys actually test stuff and people doing SPL competitions and etc are more knowledgeable than us hobbyist types. Having used a variety of stick on products in the past, moving forward I'm going to use dense non-adhesive products for floors. Makes changing seats, trans, etc easier.
For practical purposes it seems unlikely you'll notice a huge difference between brands once you get to a certain minimum quality level.

[BMR Sales]

I have always used DynaMat Lite or RamMat

[AU Doc]

...... Having used a variety of stick on products in the past, moving forward I'm going to use dense non-adhesive products for floors.......

Can you give me an example? Are you referring to something like a spray-on (or roll-on) material? Like bedliner or lizardskin?


I have always used DynaMat Lite or RamMat


DynaMat was on my shortlist, but I'll need to check into RamMat. Thanks for the info!

[chuckd71]

I don't have the box in front of me but I have used a what I think is called Stinger roadkill in floors and like it. Two layer closed cell foam and butyl combo.
I've used Rammat, dynamat (thin crap), dynamat extreme (better), dynalite or whatever it is now, peel in seal back in the day and spray on (only in places I couldn't put something worth using) and really I couldn't tell you which is which in terms of the results, at least with adhesives. Can someone in a competition car tell? Maybe. Can Joe Average driving down the road in a 50 year old rolling brick? Doubt it. Just IMO. To really do it right you need multiple layers of multiple things, and full disclosure I haven't taken the time to do it 100%, $1,000 correct.
In my experience a spray or roll on product isn't going to do much except maybe take some of the tinny metal sound out. I'm actually putting in some leftover damplifier right now, expecting very little out of one layer in a convertible, I just want it out of the garage.
Grain of salt with all of this, I haven't done anything close to being serious about this since high school helping friends out.

[dontlifttoshift]

50% to 100% coverage of a "mat" product. I use Boommat or Dynamat.

Then 100% coverage of DEI UnderCarpet lite. Done.

[csouth]

A closed cell foam/foil butyl combo would work the best. If you choose to do foil with butyl based solution, pay attention butyl AND foil thickness. I used Damplifier Pro from Second Skin Audio. Very happy with product and adhesion.

[JustJohn]

You'll see sound proofing way overdone and done incorrectly both here and on car audio forums.

As background, I used to be engineering support for BMW and Mercedes NVH applications. Basically, molded carpet with other layers to reduce road noise and vibration.

To really cover all your bases, you'll need a damper, a decoupler, and a barrier (sticky mat, closed cell foam, and mass loaded vinyl). A lot of people seem to stop at damping or try to get it to do all the work. It won't get you all the way.

Pick your favorite brand of butyl based damper. Stinger was the last one I used and it is more than adequate. Cover 50% - 75% of the intended sheet metal. More doesn't really help you but might make you feel better. Automakers usually apply something to serve this function directly to their own sheet metal and paint over it.

Decoupling the floor from you is just foam that isolates you from sound/vibration. Closed cell foam doesn't absorb water and works well. 1/4" is common as your car wasn't designed for the 4"-6" layer in modern luxury cars. Noico liner works well, is adhesive, and you can find it on Amazon.

The mass loaded vinyl is the last step and is where the real magic happens. You can find car audio brands but just buy a roll of 1 lb/ft2 of acoustic mass loaded vinyl. It is automotive grade and is what is used by BMW/Mercedes. Amazon has it and it will be expensive to ship. It is MASS loaded vinyl. Cover everything that you can with this. For curves/corners/compound angles you'll need a cement for it called HH-66 Vinyl contact cement. Basically just build a tub of you floor pan out of this material with the necessary bolt holes for seats, etc. For OE applications, this is molded between the foam and carpet.

That's it.

This guy is the closest I've seen to OE automotive, https://www.sounddeadenershowdown.com/, but still a little pricey on his materials.

Do all of the above and you'll be able to have conversations in a normal tone of voice with your passengers.

[slimjim]

I'm approaching this stage and have already started purchasing the basics, I plan to use a "mat" product, undecided which one, and the NOICO closed cell liner, I can get it nice and cheap.
I see some people go this route: Epoxy, seam sealer, raptor liner or por15, then sound deadening materials.
Is the raptor liner going to add anything at this point or is it just personal preference? I was leaning towards applying sound deadener to the SPI epoxy floor, Is there a problem with this?

[AU Doc]

This is an interesting topic, though not one I'd put much thought into. The home theater guys tend to agree that sound control comes down to mass. Attenuating high frequency stuff is easy, but controlling low frequency energy really boils down to mass. You can add a constrained damping layer (or whatever it's being called now) to improve performance.

What's most interesting about this discussion to me is spray foams (open or closed cell) have been shown to perform poorly with regard to broad spectrum sound control. They work fine for high frequency content, but just about anything does. Spray foams work great as thermal barriers, and maybe that's the piece of the puzzle they're providing here. I suppose there's also the issue of panel movement here, and I can see where spray foam products would help there as well.

[JustJohn]

This is an interesting topic, though not one I'd put much thought into. The home theater guys tend to agree that sound control comes down to mass. Attenuating high frequency stuff is easy, but controlling low frequency energy really boils down to mass. You can add a constrained damping layer (or whatever it's being called now) to improve performance.

What's most interesting about this discussion to me is spray foams (open or closed cell) have been shown to perform poorly with regard to broad spectrum sound control. They work fine for high frequency content, but just about anything does. Spray foams work great as thermal barriers, and maybe that's the piece of the puzzle they're providing here. I suppose there's also the issue of panel movement here, and I can see where spray foam products would help there as well.

Foam should really only be used to decouple, which is why it's always there in OE applications between the damping and mass layers. OE foam is also mass loaded but no where near the density needed to function as a standalone solution.

[joeko23]

Justjohn, are we supposed to use all 3 layers everywhere or just the floor, trunk and firewall? What about the roof, all 3 layers also? What about inside doors? I doubt you can fit all 3 layers inside a door. Also what about rear package tray, outside door like immediately behind door panel? Lastly, after all 3 layers are in the floor pan can we put molded carpet or do we need some padding between 3 layers then padding then carpet?

Thanks!

[JustJohn]

Justjohn, are we supposed to use all 3 layers everywhere or just the floor, trunk and firewall? What about the roof, all 3 layers also? What about inside doors? I doubt you can fit all 3 layers inside a door. Also what about rear package tray, outside door like immediately behind door panel? Lastly, after all 3 layers are in the floor pan can we put molded carpet or do we need some padding between 3 layers then padding then carpet?

Thanks!

The more surfaces you cover, the more noise you block. Sound is basically just treated as radiating from everywhere so you are essentially just building a dam to keep it out. The short answer is nothing else is needed between your sound proofing and the carpet. The decoupling layer is doing that for you.

For the guys who are spraying with Rhino Liner, that is essentially acting as the damping layer and they probably don't need additional butyl because the coverage is so thorough.

When I did my Wrangler it was a good case study because it comes from the factory with basically nothing. A few patches of damping material here and there to keep it from ringing like a bell. I did the entire floor and all 4 doors with butyl, closed cell foam, and MLV. It is not uncommon in the aftermarket and can be fit under door panels. When I get around to it I'll put a Moll panel on the rear gate and put the same thing under it. As it is, people in the rear seat can now hear and participate in conversations going on in the front seat. You can have phone conversations on the highway. I kind of have an audio thing going on with it too.

If I were doing my Impala doors (which I will at some point), I'd put the butyl on the outer door skin and the foam/MLV under the door panel.

Basically, the more you cover, the quieter it gets. When I was at IAC (part of the automotive interior division spun off from Lear), the Detroit sound lab had a front/rear roller dyno as a road simulator. The OE gave us interior noise level specs to meet. From there, we covered all the glass in MLV and used arrays of microphones to measure transmitted sound inside the vehicle. That is how "leaks" were pinpointed and addressed with additional sound proofing.

From a strictly automotive performance perspective, none of this is ideal. It's not uncommon to add 75+ lbs to a vehicle with the goal of making it comfortable on the inside. Since I'm really after more of a GT vehicle, it's a trade off that works for me.

[joeko23]

Thanks for the info, so your saying if I spray some bedliner underneath the vehicle, I will not need the layer of butyl on the floors? I am using defender pro, I think it's pretty comparable to rhino

[AU Doc]

........
This guy is the closest I've seen to OE automotive, https://www.sounddeadenershowdown.com/, but still a little pricey on his materials.
......

I'm finally getting close to putting my interior back In my car. So I'm putting some thought into this again. I double checked the prices based on what I found on Amazon with a few quick searches, and it looks like https://www.sounddeadenershowdown.com/ pricing is about the same as buying the stuff separately. Maybe even a little cheaper. It's certainly cheaper than the custom cut dynamax extreme kits for my car.

[andrewb70]

I'm finally getting close to putting my interior back In my car. So I'm putting some thought into this again. I double checked the prices based on what I found on Amazon with a few quick searches, and it looks like https://www.sounddeadenershowdown.com/ pricing is about the same as buying the stuff separately. Maybe even a little cheaper. It's certainly cheaper than the custom cut dynamax extreme kits for my car.

I've bought stuff from him and it works well. However, the mass loaded vinyl is really...really...I mean, really heavy. I would think long and hard about when to actually use it. Remember, at the end of the day we're playing with old cars. These aren't hermetically sealed modern BMWs. We also want maximum performance, and weight is our enemy.

Andrew

[AU Doc]

I've bought stuff from him and it works well. However, the mass loaded vinyl is really...really...I mean, really heavy. I would think long and hard about when to actually use it. Remember, at the end of the day we're playing with old cars. These aren't hermetically sealed modern BMWs. We also want maximum performance, and weight is our enemy.

Andrew

That's a good point. It's about 150 s.f. to do a car, and that stuff is about 1lb/s.f., correct? So another 150 lbs to the scales. I suppose the question is whether or not it's worth it for a car that will spend 95% of it's life cruising around town and up and down the interstate, and the other 5% of its life on a track. I wish I could say those numbers were reversed, but unfortunately, the good Lord decided to make me good looking instead of wealthy :)

Still. Lighter is always going to be better. Even on a cruiser.

[AU Doc]

EDIT: Double Post

[andrewb70]

Cruising around town the difference is negligible, at least for me, because I generally have my windows down. There is a bigger difference on the highway, especially with the windows up. The exhaust also plays a major role. If it's loud to start with, it is very difficult to deflect all of the sound.

Personally, I would put sticky stuff on the roof, firewall and inside the doors, then assemble the car and see how it goes. If it is too loud, start on adding other stuff to the floor. I would also recommend some kind of heat blocker for the front of the floors right away. The heat from the exhaust will definitely come through, especially when just cruising around town.

Andrew

[JustJohn]

This keeps coming up so I decided to summarize some of the information from my previous career. I used to be involved in the manufacture of interior acoustic control for BMW and Mercedes. The plants in Greenville, SC and Tuscaloosa, AL are supplied from Greenville and Spartanburg, SC. During that time, I had regular meetings at the BMW facility as well as travelling to the development center in Stuttgart for Mercedes to work on upcoming models. Here is a summary of the whole process from my former company:

Interior component prototypes for interior noise reduction are developed in a pre-production vehicle on a dual axle dyno which can accommodate speeds up to 125 mph. Exterior transmission surfaces, like glass, are covered with 1 lb/ft^2 mass loaded vinyl to block sound from surfaces not being studied. During the dyno runs, noise levels are measured inside the car by an array of microphones arranged on a grid. The array is aimed at various places in the interior to determine where most of the transmitted noise is coming from. This is to determine where to apply sound damping material and is mainly a cost cutting exercise. The materials used are relatively expensive and even luxury automobile producers do not overspend on construction. The effective hobbyist approach is to cover as much as is feasible.

Here's what BMW and Mercedes do:
Damper is applied directly to the body at the factory under the paint. It's butyl-based and not that much, about 50% - 75% coverage max. If you've ever pulled carpet from a new vehicle you've seen it. Just some "thicker" material here and there that was painted over in the factory color. It's enough to get rid of resonance, nothing more. I think that is often misunderstood about damping material but the most easily demonstrable. A bell does a good job of resonating and is described as ringing. Apply damping material to the bell and it no longer resonates. I think Dynomat uses this as part of their marketing. If you ring a damped bell, the initial sound is just as loud as before but there is no resonance. It's just a thud. Good, but there's more to NVH control.
For the interior carpeting, what most people do not realize is that it is several inches thick in modern (luxury) cars. Roughly 4-6 inches and just the carpeting can weigh 50 - 60 lbs. The car has this designed in and here is the composition:
1. Isolation layer of mass loaded foam. Exactly what it sounds like, it is a two part molded foam, mixed at the molding process and loaded with a carbon-based material to add mass. This layer isolates the interior from exterior vibration and keeps the thud of the damped car body from being transmitted to the passengers. I just recently found this commercially available in the aftermarket. A good compromise material is closed cell foam. It does not absorb water and is available in rolls and sheets.
2. Mass loaded vinyl. 1 lb per square foot and about 1/8" thick. This is molded on top of the foam and blocks transmitted sound waves. This is the screen that keeps out ambient noise, especially the higher frequency sounds that most people can here. This should cover everything you can get it to cover with as few gaps as possible. By definition, this stuff is heavy and is not cheap to ship.
3. Carpet. I feel like this is self explanatory.

For the firewall pad, it is mass loaded foam and mass loaded vinyl.

That's all there is to it if you are aiming for a quiet ride. Damping the sheet metal, isolating the interior, blocking sound. The materials to do these three things are well established and readily available.

I put a high end stereo in my Wrangler a couple of cars back and went through this exercise. From the factory, a Wrangler has some damping and some carpet. Conversations with the back at highway speeds are not feasible. After adding 75% coverage Stinger butyl damping, NOICO closed cell foam and mass loaded vinyl (it's all on Amazon), I achieved a 6db reduction in ambient noise (3db is percieved as twice as loud).
Doing more than the above is a fun over-engineering exercise but will only add (more) weight and not really improve the results.

[AU Doc]

Thanks for the detailed info!

Let me see if I understand correctly. The process would go something like the following:

Calculate the surface area inside the car.
Order damping material/vibration damping/CLD tiles/etc. to cover 50%-75% of that surface area. Also include anything inside the car that may be prone to resonating like the dash, correct?.
Order CCF (or mass loaded foam) and MLV to cover 100% of the surface.
Apply damping to surfaces that are prone to resonate. E.g., inside doors, behind the dash, a few places on floor pans, wheels wells, roof, etc. Anything that looks like it will vibrate and resonate.
Apply CCF (or mass loaded foam) to 100% of the surface. Is this necessary for places that are not in direct contact with the occupants? E.g., inside the doors?
Apply MLV to 100% of the surface
Install carpet
Enjoy your quiet ride :-)



It sounds like the area where hobbyists go wrong is in apply too much damping material. That said, I can see where if you don't know how much is enough, you just over do it to be safe.

I don't suppose you have links or can recommend specific products or suppliers for each of the materials?

[JustJohn]

Basically that's it.

Anything you can see in the interior can broadcast noise.

I don't have much for commercially available product recommendations other than what I've personally used. Confirming the density and materials is really what you need.

I have used Stinger butyl damping and Noico foam. The MLV I just order from Amazon and it doesn't seem to have a trade name attached. There's also contact adhesive specifically for vinyl, which is pretty useful when building complex shapes: RH Adhesives HH-66 Industrial Strength Vinyl Cement.

[Jeremy]

I recently purchased my MLV from Acoustical Solutions. In talking with the sales rep, it is virgin MLV. I did the trunk first and it made a difference. I wasn't sure how much it was going to help since the trunk is pretty sealed from the interior. It seems to have helped lessen the road noise and mechanical noise from the back. The stereo sounds like I added some power. The biggest difference I noticed from doing the trunk was bumps seemed softer. I know it didn't make any difference on the suspension, but the energy transmitted through the body from bumps seemed much more subdued. Any bumps that used to feel like a "thud" are gone now.

I just cut it to match the factory pad. I haven't had time to go back and seal the vertical voids.

Next up was the door splash shields. This was well worth it. Easy to fit and the doors just feel more solid.

Next step is to pull the rear seat, arm rests, sail panels, and package tray and get everything covered.

I did play with a heat gun and the MLV. I could never get it to mold to a compound curve, but it will hold linear bends really nicely. I wrapped a piece around a piece of 1x lumber and it is still in the shape of a "C". I plan to bend any angled transition pieces with wooden jigs and heat. I'll then glue them together with the HH-66 cement. This should help it better contour to the body and should help hold things in shape.

[AU Doc]

Does anyone know which Velcro I should use for attaching MLV? Sound Deadener Showdown had one that was hight temp and vinyl compatible, but they've shut down, and there's no part number that I can find. Google hasn't really turned up anything specific.

[Jeremy]

Played with the MLV more today. I did behind the rear seat back, below the cushions and over the hump. The MLV is fairly easy to work with. I did find that I had to be willing to "waste" a piece as I worked up the patterns. I made an initial pattern out of some left over EPDM Rubber I had. It bent a little easier than the MLV. What ended up happening is that as I worked the MLV it would lay down a little different than the rubber. I had to add relief cuts in places and let it slide or overlap as it wanted to. It laid down fairly nice but the first pattern ended up too small as it conformed to the floor pan. I marked on the first pattern where I needed to add material and cut a second piece and it fit great.

The HH-66 cement worked well. I did find that you have to let it really sit up before trying to glue the pieces. If it was at all wet, things slid around.

The results were well worth it. I could not even hear the exhaust at idle. Interior noise seemed less. Stereo volume was lower to be comfortable and allow conversation.

I'm doing it in stages as time allows and what I can get to fairly easily.

I think the next step will be to remove the console and front seats and do the main floor pan.

This will leave the wheel wells and rear shelf but those areas require more effort to get to. The wheel wells are also a little more complicated due to the curves and I should have more experience with the material by then.

The MLV is not cheap but seems to work. I tried some in the trunk of my 2007 charger. I cut a piece to fit on top of the lower trunk panel as that was the only flat spot. I wanted to put it under the panel, but the way it is molded there was not enough room. Just sitting on top of the carpeted panel, it really took the edge off the flowmaster exhaust on the highway. I bought the car used and the exhaust was on there. It seems to work well with the combo based on the dyno slips that came with the car but was a little grating on longer trips. Not anymore.

[Just 1 More]

Once you put down the matting like Dynamat or Noico, how do you remove it if you ever need to?

[rsrguy3]

This keeps coming up so I decided to summarize some of the information from my previous career. I used to be involved in the manufacture of interior acoustic control for BMW and Mercedes. The plants in Greenville, SC and Tuscaloosa, AL are supplied from Greenville and Spartanburg, SC. During that time, I had regular meetings at the BMW facility as well as travelling to the development center in Stuttgart for Mercedes to work on upcoming models. Here is a summary of the whole process from my former company:

Interior component prototypes for interior noise reduction are developed in a pre-production vehicle on a dual axle dyno which can accommodate speeds up to 125 mph. Exterior transmission surfaces, like glass, are covered with 1 lb/ft^2 mass loaded vinyl to block sound from surfaces not being studied. During the dyno runs, noise levels are measured inside the car by an array of microphones arranged on a grid. The array is aimed at various places in the interior to determine where most of the transmitted noise is coming from. This is to determine where to apply sound damping material and is mainly a cost cutting exercise. The materials used are relatively expensive and even luxury automobile producers do not overspend on construction. The effective hobbyist approach is to cover as much as is feasible.

Here's what BMW and Mercedes do:
Damper is applied directly to the body at the factory under the paint. It's butyl-based and not that much, about 50% - 75% coverage max. If you've ever pulled carpet from a new vehicle you've seen it. Just some "thicker" material here and there that was painted over in the factory color. It's enough to get rid of resonance, nothing more. I think that is often misunderstood about damping material but the most easily demonstrable. A bell does a good job of resonating and is described as ringing. Apply damping material to the bell and it no longer resonates. I think Dynomat uses this as part of their marketing. If you ring a damped bell, the initial sound is just as loud as before but there is no resonance. It's just a thud. Good, but there's more to NVH control.
For the interior carpeting, what most people do not realize is that it is several inches thick in modern (luxury) cars. Roughly 4-6 inches and just the carpeting can weigh 50 - 60 lbs. The car has this designed in and here is the composition:
1. Isolation layer of mass loaded foam. Exactly what it sounds like, it is a two part molded foam, mixed at the molding process and loaded with a carbon-based material to add mass. This layer isolates the interior from exterior vibration and keeps the thud of the damped car body from being transmitted to the passengers. I just recently found this commercially available in the aftermarket. A good compromise material is closed cell foam. It does not absorb water and is available in rolls and sheets.
2. Mass loaded vinyl. 1 lb per square foot and about 1/8" thick. This is molded on top of the foam and blocks transmitted sound waves. This is the screen that keeps out ambient noise, especially the higher frequency sounds that most people can here. This should cover everything you can get it to cover with as few gaps as possible. By definition, this stuff is heavy and is not cheap to ship.
3. Carpet. I feel like this is self explanatory.

For the firewall pad, it is mass loaded foam and mass loaded vinyl.

That's all there is to it if you are aiming for a quiet ride. Damping the sheet metal, isolating the interior, blocking sound. The materials to do these three things are well established and readily available.

I put a high end stereo in my Wrangler a couple of cars back and went through this exercise. From the factory, a Wrangler has some damping and some carpet. Conversations with the back at highway speeds are not feasible. After adding 75% coverage Stinger butyl damping, NOICO closed cell foam and mass loaded vinyl (it's all on Amazon), I achieved a 6db reduction in ambient noise (3db is percieved as twice as loud).
Doing more than the above is a fun over-engineering exercise but will only add (more) weight and not really improve the results.


This came to me at the perfect time. Thank you John and Mery Christmas!
Looking into the lizard skin spray on or raptor liner as a first coat.... Just don't know which yet.

[ButterCharger]

Came across this thread in my research for doing sound deadening in my 68 Charger and wanted to thank you all for the info! If anyone know of any other good resources to continue learning about this, let me know :)

Edit: I found some really good information on the ResoNix Sound Solutions website. For anyone interested in the topic, search for them and look for the resources section on their site.

[Vimes]

On the subject of sound control, has anyone thought about replacing body mounts with gel mounts to control sound transmitted from the drivetrain? Sound travels through metal very well, and the drivetrain only attaches to the body at X number of points, so isolating sound at these points should knock some noise down. I've thought about trying it on my project as the cab only has 4 or 6 mounts, IF it ever gets to that point. These are the ones I was considering, but won't call the company to discuss until I'm closer to that point.

https://ph.parker.com/us/en/product-list/lord-fluidlastic-mounts

[nekkidhillbilly]

i bought some knock off stuff offline. im cheap.