Sound Deadening Advice
 

When I pull the carpet to install roll bar, I want to put sound deadening behind seats and on parcel shelf. Main goal is less exhaust noise (low frequency).

I have Dynamat, but understand some folks have used Relectix.

Please give experiences, results, advice.

This thread is relevant to my interests

I used fatmat all over mine. worked well.

Cheaper option:

https://www.parts-express.com/sonic-...-x-13--268-030
https://www.parts-express.com/sonic-...-x-40--268-035

This is what I will be using to cover much of the interior of my car.

I used the fatmat (dynamat knockoff) and ensolyte foam. Everywhere.
The mat is for the vibrations and the foam is for the sound.
Later I found out that there's a science to it, and really not needed all over the whole car, but in strategic locations. Oh well.
My white miata was the plushest/quietest na/nb I've driven.

Dynamat
Closed cell foam over the top of that
Barium loaded vinyl(heavy but holy shit effective)

As Vlad said, my Miata, even with a loud ass 3" exhaust, is dead quiet. Literally zero road noise for how stiff the car is.

Worth the extra 50-100lbs imho. I spent around $4-500 total and don't regret it.

As above, dynamat, and 'luxury liner' closed cell foam all ovah.

There are 4 sound conducting corridors from the trunk area to block with a wall of foam or something...

All my noise comes from the firewall now. I need to pull the dash and do that area too.

It's fun to walk along the car, and rap on it with my knuckles- The front fenders have this hollow tinny noise, but once I get to the doors it becomes this dull-ass thud with zero resonance. Boner.

I too have luxury liner pro. It is a bit heavy, but extremely effective. Unlike other products it does not glue down so can be easily removed. I have it under the door, on the back / top area behind the seats and in the trunk. Trunk made the most difference.

In true budget DIY Miata style, I think it should be fair to at least note that you can get a butyl roof flashing (if I recall correctly) at Home Depot Racing for a hell of a lot cheaper then actual dynamat. I used a Pella brand and it came in a roll with the fancy aluminum backing just like dynamat. Everyone else hit it on the head though, MLV along with closed cell foam is what really blocks the noise.

I've been reading about this some. Not the same balpark as fatmat, but I could do my entire interior for $25.

I want to at least add some deadener and foam to my doors.
I've shoved some packing foam in the easier to access crevices on either side of the gas tank. It didn't cut down any decibels on my app at 70mph, but it did seem to have removed certain frequencies.

I want to use some strategery and see if I can reduce the noise without adding a ton of material.

Care to share the identity of these "strategic locations"? I'd like to try this out but don't want my whole interior coated.

It isn't so much per car specific placement. Dynamat should be used as and IS a vibration dampener. It isn't a sound deadener. It stops vibration between connecting panels and sound vibrations in the middle of large panels.

So use of dynamat should be used where panels are connected together, their seams, and in the middle of large panels to stop or deaden vibrations that occur across large surface areas.

The blanket technique isn't necessary but if you don't know what you are doing I'd effective. It just costs more and is heavier.

That sounds easy enough, thanks for the tip.

Always a good read

Welcome to Sound Deadener Showdown | Sound Deadener Showdown

yeah it was an article/writeup I read, I don't remember the details, but I think it involved tapping/knocking on panels and depending on if they resonated/etc you'd put that stuff on. The whole "tinny" vs "dull" sound test.

I'll try to find it when I can (though I'm sure there are millions of other writeups just as good)

I just bought 100sq/ft of the stuff, and it was WAYYY too much for a miata, so I just went nuts and covered every surface. And even still had like 40sq/ft left over LOL

I've used this on my pickup truck with some success. It is self-adhesive and will effectively reduce the "boominess" of the larger panels. It reduces resonance by absorbing vibration in the larger panels. It will have limited effect on smaller panels. It is very inexpensive and was recommended to me by someone with a Tacoma that was amazed with the difference it made. He had used Dynamat in the past and equivocated the two, but I make no such claim since I have no experience with Dynamat.

I imagine it would be useful on the back package tray and front-facing sections of the package tray behind the seats of the Miata.

Does anyone have experience with the butyl Home Depot material in hot environments? I've heard they give off a tar smell when heat cycled over, say, a southern summer.

No issues in my location.

Small update / correction:

I actually have DEI brand Boom Mat. Prettly close to Dynamat. I used strips of this on the doors and it helps a lot with reducing tinny sound on closure. Now most of the sound seems to be from the rear fenders, not the doors.

This indicates that blocks / strips will work as well as full coverage, which makes good sense as the desire is to stop panels from freely vibrating.

So the plan will be to place patches on the parcel shelf and behind the seats, then cover any actual holes, then cover everything with SOMETHING.

Would like to just put a layer of MLV without the closed cell foam, but I'm not sure how effective that will be.

Luxury Liner is now produced without the attached foam, but LuxLinPro has the foam.

Here is a company that sells MLV at a much better price with shipping, especially if one gets 40 sqft: soundaway

Has anyone installed the MLV without the foam layer? If so... results.

I installed some similar items I got from Menards;

-WeatherGuard (Peel-N-Seal copy) - only a few fractions of an inch thick, this provided a good stop to vibrations.
-Frost King duct insulation (Similar to Dynamat - has aluminum backing - USE GLOVES, CAN and DOES cut fingers if you aren't careful around cuts)
-Reflectex duct insuation - (tranny tunnel and floor only) This kept transmission tunnel heat out of the car.

This was installed on the:

-Door panels (inside of outside skin, inside of inside)
-Floorboards and transmission tunnel
-Behind the seats and in the trunk

Overall, before install the car was a beast as far as noise. It was loud and not quiet about it. However, post install I found the sound dramatically decreased and unless I'm boosting, driving over harsh road surface (or have bad tires) I can only hear the exhaust for the most part.

We have to pull the dash to replace it and when we do I will be adding damping material to the firewall as well. This is where the majority of the noise and heat comes from now, though I have yet to do the panel behind the seats as well (I have a vibration in there on my car too...)

Overall weight gain was probably less than 10 pounds, overall enjoyment of car with no A/C? Cross country tour approved.

I have a bunch of "Peel 'N Seal"-style stuff in one of my cars, it did indeed smell a bit for the first few days, but it got better over a week or so. The smell came back on hot days when the car was parked in the sun, but only for the first month or two, and I didn't find it to be overpowering. This was in the doors of a Volvo 940 to help keep the inner door parts from vibrating with the door speakers.

I just had this conversation with a friend who used it all over his old bronco restoration. He said after the initial off-gas on day 1 it was fine thereafter in any conditions.

https://www.miataturbo.net/attachmen...ine=1425355084

Three laters of Fatmat from the parcel shelf to the front of trans tunnel, both doors and trunk. Most of my noise is now coming from the firewall and under the dash. One day I'll get to that too. Sometimes I forget how quiet my car is until I sit in my friends NA or someone else's miata without any sound deadener. Ive also noticed my transmission tunnel and floorboards stay much cooler in hot temps then they did before. In total added about 20lbs to the car.

Definitely worth doing.

I used a 3M 'Mass damping' product first. Adhesive back, very flexible and workable, about 3mm thick rubber type matting. Cabin, inside of door skins, boot floor etc.

https://www.miataturbo.net/attachmen...ine=1425387474Insulation by simonholehan, on Flickr

Then a foam/felt type matting, whole interior, up the front firewall and rear bulkhead, the parcel shelf etc.

https://www.miataturbo.net/attachmen...ine=1425387474Felt carpet 2 by simonholehan, on Flickr



As the other posters have stated - its definitely worth the effort if you have a big project with dash out etc. Small weight penalty outweight by the big improvement in comfort and road noise.

This guy probably has IMO the best example of proper sound deadening.

Snotrag, could you give a P/N for the 3M product?

18PSI, same thing, which Ensolite did you use. I ask because Ensolite appears to be a tradename and they produce a lot of different foams.

I cant find the original details in my email, or where I bought it from, but after a little searching I think it must have been this stuff -

PeaceMAT? XXL Car Audio Deadening Insulation 3mm 5Kg Car Heavy Layer Deadening (3m Roll) Car Audio

3M 'peacemat'

it was really nice to work with as its stretchy, so I could fit it quite well over the humps and bumps in the floor as per the picture.

Worked at 3M for a few years doing NVH R&D work and your setup looks very good, you may try some 1/4" foam with that 3mm mat on top, a de-coupled barrier wirks really well on the shelf behind the seats that flex and reberberate the noise bouncing around in the trunk.
How do you like this dyno?
Attachment 184296

Thats good to hear! Yes, very please with how it turned out. You can also just about see in those photos where I seam/stitch welded the door openings too, which I think was another incremental improvement in NVH.