How to Soundproof Your Car - Discussion Thread

Sound deadening is coming up in another thread, so I want to throw this out there for discussion.

I read an article a few years ago about auto soundproofing. The author maintained that simply slathering every surface with Dynamat was heavy, expensive and far from ideal. Instead, he stated that a single patch of Dynamat (or the like) on a large area of unsupported sheet metal (like a door skin) was all that's needed. Beyond that, a layer of foam surrounding the cabin would yield optimum soundproofing for the cost.

I filed the info away in my brain until one day I removed the door panel from my BMW. That car was easily the quietest car I've ever driven. I could whisper in the front seat to passengers in the back seat at 75 MPH. What I found in the door was exactly what the article described. There was a single, small, thin patch (maybe 1/8") of asphalt deadener on the door skin and a layer of light 1/2" foam behind the panel.

I've tried, but cannot locate that original article. Instead, here's another that outlines the same general process without as much explanation.

http://www.quietride.com/auto-acoustics-101.htm

I know our 3g's have almost no sound deadening, so they might really benefit from a similar approach. It would be the ideal balance between fuel economy, cost and quietude.

Any thoughts?

I have seen similar applications on panels on my Z when I was working on it recently. Unfortunately I did not take pictures of that area. I also have heard the same complaints about Dynamat. If we were to use it heavily on a light and "slightly powered" car, it might produce noticeable performance drag. I am going to look into this as my interior will be a late winter/earl spring portion of my resto. Great to bring this up Dr.

What soundproofing our cars did have was just as you have described. Small portions of sound deadener (Think the small black squares in our trunk areas). Although it didn't work out too well for us, maybe more efficient material would be better.

What do you guys think about using an aluminum backed, self adhesive, tar paper for roof repair as a sound deadener? The stuff I found at home depot is decent and not as heavy nor expensive as the premium stuff like DynoMat. I think a 6" x 50' roll is 17 bucks. It could still be used sparingly. Only thing I worried about is the smell of tar in the hot weather months...

I had a small quantity of DynoMat scrap that a friend gave me. I pulled the interior out of my 07 civic and cranked the stereo. I used just enough to settle the rattles and not coat the entire interior of the car. It worked out just fine.

Peel N' Seal is all over the internet as a cheap Home Depot alternative to Dynamat, if that's what you are referring to. You might do some reading to see if smell comes up in the comments. I would definitely try it out if I were working on that.

Im gonna have to sound proof my car. ever since i installed the mounts my car vibrates alot more than it use to and wanna limit the vibrations more. That is less likely to happen since i am going stiffer on my suspension. thanks for posting snooz

I used to be a general contractor and we used a peel and stick material (white I believe) to seal around windows. The "tar-like" substance was very sticky and I recall no specific smell. The only problem is that it only came in 4" wide rolls. Has anyone found sheets of the stuff?

The big problem with the roofing materials is that it can get hot enough in the car to soften. I've seen it slide a few inches down a door over a summer. Some of the other "good" materials are similar in high heat performance, so it's a good idea to check what's out there right now, and who has the best deals.

i have dynomat on my front doors and it made a big difference. I asked a professional audio installer and he said that you dont need to cover the whole car you have to become an engineer and check out where the noises are coming from. he told me that most of the road noise will come from the wheel well so to cover all 4 of them up. also spray some more undercoating outside the car to help the vibrations cancel out. he also said that the firewall transmits alot of vibration into the cabin so to dynomat the inside of the firewall. for my trunk i only added patches to keep the weight down.

I must agree with those who say a total Dynamat is a waste of money and adds a lot of weight to the car.
A small piece on each pannel is enough to keep it from resonating, and make it 'dead' for sound pressure.
If it's road and suspension noise you want to get rid of, it's better to do it all with a 'çarpet' like material.
I put in Dynamat up to the windows, i could not stop with one box, i liked doing it too much.
It added some serious weight, but the result is amazing.

I've put that sound deadening shit all over the car and I regret it. In retrospect a few on the door panels would have sufficed like snooz said

is your goal to keep outside noise out? then you might want to think about sealing the undercarriage, I had it done to one of my cars a long time ago and it seemed to help a little bit. I haven't looked into that sort of stuff in awhile.

Old thread, but it has been bumped so I might as well chime in.

It really depends what your main goal behind soundproofing is as to what method and products will work best. Is your goal to make the cabin quieter? or is your goal to improve audio quality? In a sense making the cabin quieter will help the audio, but if audio is your main goal then there are a lot of different ways to achieve this rather then just slapping a bunch of dynamat type of product all over the sheet metal. I have competed in IASCA competitions with my car and won numerous times without having any added sound deadening in the car at all. For this coming season though I will be adding sound deadening and then tuning the stereo with the help of a friend and an RTA.

I'm at 3 layers 100% coverage on floors, roof, and outer door skins. have about 25% coverage on inner door skins.

Car rides down brick roads and you would swear you were on smooth pavement. lol

But you are right, take a small hammer or even your knuckles, rap on metal in your car. If it does more than go thud start with 25% coverage of good deadener and add until you like the result.

Also for those who don't know. Do not use Peel and Seal. That stuff is for roofing only. Let me go look and i can find a nice video for those who don't believe me.

Reviving old thread. I'm replacing my dash soon before winter and want to make the car more quiet but don't want to add much weight. So it looks like I need dynomat or equivalent on the firewall, wheel wells, and a little on the insides of the doors. What about everywhere else the factory stuff is there already, like the entire floor. I plan on removing that since it's as hard as the metal.

I've been thinking about this thread recently. I'm slapping in bits of peel-and-stick roof patch to the insides of my cabin whenever I remove interior panels. There is no noticeable smell from it at all. Still, the car is a thunderous 70 dB at highway speed. By contrast, my work truck (so basic it has vinyl floors) is only 60 dB. There doesn't seem to be a great deal of engine noise coming through my firewall, so if I were doing your project, I might simply replace the original jute and call it good. Same thing goes for the floor, although a good underbody coating would probably do wonders for road noise. For the sides and ceiling, my plan is to get something like neoprene foam for lining all the panels. The neoprene is the key, I think, and I expect it to do wonders.

When you say jute, are you referring to the stuff on the metal that you have to get off with dry ice or the fabric insulation on the bottom of the carpet?

Ive been researching this quite a bit in the past day and almost every how to guide is from someone who has never done it before and really has no idea what they are doing. I'm trying to find a professional who has done this hundreds of times who has an article or youtube video.

Here is what I got so far.

- remove the old sound deadener from the metal with dry ice or canned air upside down in hard to reach areas.
- i think I'll get Norco 80mil sound deadener to apply to the entire firewall, wheel wells, floor, and cover 50% of the inside doors.
- next is to get some kind of foam for the inside doors and other places to absorb the sound. This link below list several different type of materials I will look into more.

https://www.sounddeadenershowdown.com/products

There does seem to be two steps to this process. One is to add mass the panels to reduce noise creation, then the other is to add foam to absorb the noise that still gets through.

Sorry. Yeah, the recycled denim looking stuff. I honestly don't know what it's called, but I've heard "jute" used at least once before.

What do you mean by "professional"? The car stereo professionals will put a 1/2 ton of Dynamat in and call it good. If you want to see how the OE design engineer pros do it, go to the junkyard and look for a S-class Benz or 7-series BMW.

By now, most of the OEs are using this too.

https://www.electronicdesign.com/automotive/reducing-unwanted-noise-automobiles

To improve the soundproofing, we used a noise-insulating synthetic rubber, Comfort Mat Vision.

Is it heavy?

No, the material is applied in a second layer to the vibration-absorbing material. Carefully tear off the release coating. We apply the material to the surface to be glued. Press carefully, it is important that there are no air bubbles between the surface and the material. For best performance, sound absorbing materials need to be glued joint to joint.

Do you have a link?

No, unfortunately not.