This entire thread is highly subjective as to my descriptions, and I am not a trained acoustical engineer nor soundproofing expert, so if you have any comments please keep this in mind.

I have always admired the ability of many cars (notably VERY expensive and heavy ones) to be almost completely silent when driving. I was after a little more peace and quiet in my 93 VR Touring especially from tire and road noise.

After 75,000 miles I had my share of squeaks and rattles, and I was able to elimate most of them by tightening up lots of fasteners on the frame and suspension, and by methodically padding a lot of the interior plastic trim pieces with thin sheets of closed cell foam with adhesive backing to keep them from squeaking. A new set of tires would undoubtedly give some significant gains as well but mine still have lots of tread to go...

I intend to soundproof the entire interior this winter, and decided to start with the doors, then firewall, tranny tunnel and entire rear interior. I'm going to skip the floor and headliner since the Touring model came with extra soundproofing there, and I doubt if I would see any gains worth the hassle.

I recently completed both doors but I did not use "Dynomat", which is pretty much just a loaded vinyl with a dead soft aluminum barrier and sticky backing. From what I can ascertain, the aluminum does most of the "barrier" duties and also provides "dampening".
It is not a sound "absorber", which due to space constraints would be pretty much impossible to install on the doors.
I did find a roll of 2" X 50' roll of "flashing tape" that can be found at most plumbing specialty stores, it's made by Polyken. I could not find it at Home Depot.
It's essentially the same thing, but instead of sheets, it comes in a roll.

The cheapest I could find Dynomat brand worked out to $5.00 a sq. ft. in sheets, the tape worked out to $1.60 a sq. ft. Due to my my Scottish nature, you can deduce which one I used.

Due to the many complex curves on the door panels I also thought the tape would be much easier to install since you need to follow the contours exactly in order to fit the panel back on - there is no "wiggle" room. If you've ever watched an expert put window tint on a curved rear window you'll know what I am talking about.

I pulled of all the fasteners, door handles, Bose speaker and plastic wire holders I could in order to make a more seamless application. I sprayed the bare metal with Windex in order to get any dust off and to help the tape to adhere. I started by applying vertical strips and butted them edge to edge - the sticky vinyl backing squashed together nicely to eliminate any gap. Over the large "oval" opening I overlapped the strips by 1/4 inch and pressed them together with my fingers. Each door took about 3 hours from start to finish, but I did cover it completely with no gaps, and the trim panels fit back on with no problems.

The results so far? On the exact same stretch of road at the same time of day I recorded a 3db reduction at 50 mph by my passenger using a cheap Radio Shack db meter sitting on the dash. The doors close with a more solid "thunk" instead of a metallic hollow sound.
To me, the Bose stereo seems to have more "punch".
The interior does seem a little more hushed, but it's really hard to describe what 3 db's sound like, even though that is a significant reduction.

Next up, the firewall and tranny tunnel with some heavy ribbed black vinyl "carpet runner" from Ace, and 3M Super 90 Spray glue. If I can get to 10db reduction overall I will be ecstatic, but I have a feeling I've already gotten the biggest gains.

Picture attached:

 

Good thread, now I have to do something about my car being so loud inside. I guess I have to wait until it gets warm out. Good luck with your task.

 

looks like a lot of work, but i never really thought about that as an alternative... good one

 

Yeah, I did mine at 70F, but I think it will stick pretty good even at lower temps if you get the surface really clean... looks like a good spring project for you. Stay warm. BRRRRRRRRRR. (God I love Tucson...)

 

Not to bad really, you just have to patient and take your time. Good beer helps.

 

When I gutted my car to deinstall the previous owner's stereo I did the doors as well. I forget the grade but I used one of the heaviest Dynomat makes and covered the backsides of both door skins. It made a very nice improvement not just to the stereo but to the road noise just as you describe. Highly recommended.

 

I think the tape I used is equivalent to a mid grade Dynomat. I guess the tradeoff is always weight vs. sound reduction vs. price.

The "extreme" dynomat seems to have a thicker metal coating, but at an extreme price.........

Damn, I'm cheap, but a good tipper.

 

Hey Ron, what do they use for airplanes?

 

Hey Ron,

Glad to see you're going forward with the project. What weight material did you end up using (i.e., 1.0 pcf)? To be perfectly honest, most people would have a hard time reliably detecting a 3 dBA change in level. Did you have the Rat Shack meter set to "A" or "C" weighting? I think if you go back and forth, you may see a noticeable difference. A-weighting was developed to approximate the non-linearities in our hearing but in reality, it frequently sucks (industry terminology there...).

I expect you would achieve the greatest reductions by treating the firewall, driveshaft tunnel, and hatch floor. But as I pointed out to you before, you will eventually hit the limitations of sound transfer through the glass and seals of the body.

Keep us updated, this is good stuff!

 

I remember one of our club members put Dynomat on the inside of the outer sheetmetal inside the door. His doors closed with a very satisfying thud, unlike the tin can noise my car makes. It does add weight, but I think sound deadening is dependent on the weight of the deadening material. I want my car to be light, but it was such a nice improvement that I would consider doing it despite the weight gain.

Does anyone know of a McMaster-Carr equivalent to Dynomat? It seems like there would be some industrial material that would work well for lower cost.

-Max

 

Specialty composite stuff in all kinds of different grades and dampening materials.

It's super high tech and really expensive. You generally only see a complete soundproofing job on high end biz jets, never on light planes except for a firewall barrier. Comes in rolls 50 feet long only, and to do the interior of a car properly it would take 4 or 5 different types of material.

I might consider marketing a kit with pre-cut pieces and instructions where to place them, but the cost would be probably way too high, and it would take your average guy a week to install it all. The whole process is kind of voodoo unless you have an applications engineer, acoustical engineer and testing equipment available.
All the composite stuff has to meet mil spec standards for flammability, out gassing, etc.

 

I have no idea how much it weighs. I guess I could put some strips together and weigh a sqaure foot just for fun at the Post Office! I used the "A" setting. I really could not discern a difference while I was driving. this is such a crap shoot, I just hope the cumulative effective of the different areas will add up.

 

I considered putting it on the inside of the exterior door sheet metal also, (does that make sense?) but it was just too awkward to get in there to cover it without taking the window and assembly apart. I do think just a couple of sheets would be a big help, even it was not covered completely, and I may just spring for the real Dynomat Extreme to do that. Spray acoustical foam or spray undercoating might work but I could not justify the expense and probablility that I would get stuff all over my window tint or power window assembly. From what I've read, sealing air gaps is paramount, since sound will transmit readily through even tiny voids.

I've done extensive searching for something comparable to Dynomat and this tape is the only thing I have found.

It has cost roughly $20 in materials so far........

One interesting negative side effect: The cabin seals so completely now I have to crack a window to get the door to shut without really slamming it hard.

 

Is there a difference between flashing tape and aluminum foil tape? I bought some aluminum foil tape at a hardware store but it does not have any loaded vinyl on it.

 

www.b-quiet.com

Cheaper than Dynamat, Out-performs Dynamat, More plyable than Dynamat.

This was the stuff I'd intended to use on my SPL car. Great great stuff. They also have a "paint" you can use to get into any tight spots (inside door panels, etc.)

 

I have had absolutely no luck finding flashing tape locally. Any ideas?

 

Great thread, interested to hear how you progress.

 

jesus christ.........no really, he was the op, did you see the date on this scroll.

 

If you guys are looking for cheaper Dynamat, just get the FatMat off Ebay ... in bulk it's a great buy, and is very pliable and stays put forever. The paint on stuff from the same seller is good too, it's good to spray it inside the doors, in the A and B pillars, and in the rocker panels. Also any other hard to reach spots. And you will get a benefit from doing the floors, even on a Touring. The floors are where most sounds comes through on any car. Another thing you can do that will make a small improvement of how your speakers sounds is pack the doors with polyfill, and if you have rear speakers then pack the B pillars too.

 

3 db is very good. in stereo terms thats like cutting half the power of an amp to loose 3 db.

 

Thanks for sharing