To those who have "sound proof'd" their cars...

[UNHCLL]

Did covering the majority of the car with a product like FatMat, Dynamat, etc. (Not some roofing tar crap), actually make an appreciable difference?

How big was the weight penalty? IE: did you use 4 rolls at 15lbs a roll?
Did you do the whole floor, 1/4 panels, doors, etc?

Thanks,
Chris

[Jean]

I know it's not apples to apples, but when I did this 10? years ago on a 2nd gen integra with my brother we did it from the firewall to the trunk..including doors and such. Everything except for the headliner basically was done. It made a HUGE difference, in road noise and sound quality. I want to say we used about 60-80 or so square feet or "brown paper" (similar to dynamat)...it had a sticky backing and was fairly thick.

[fiftytakedowns]

I believe Luke has some stuff that he can chime in at, there are some ones that arent too heavy, that do cut out road noise pretty good.

[Jalves619]

I actually went to SecondSkin's warehouse last week to check out some of their products and see if I wanted to soundproof the e30. What I found was that while their stuff was great quality, the oem e30 sound deadening far surpasses what they offer. The luxury liner pro is way thinner than the factory foam/vinyl mat combination under the carpet. e30s already have tar panels to deaden the resonance of larger surfaces and MLV(mass loaded vinyl) to absorb sound. I'm sure you could add a bit in specific places but I'd think that doing a full layer would be a waste. The difference it would make on Acura will be far more noticeable than it would be on a BMW.

[bmwman91]

I applied Damplifier (Second Skin product) on almost every surface (except the firewall). It made a huge difference. I stripped the factory tar since the Damplifier does not stick well to it. The 318iS has less deadening than the 325, so that might be why I saw a huge improvement.

The biggest difference was made in covering the inside of the door skins.
Covering the floor pan also made a big difference. I put in 2 layers in the large central portions.

Then I put 1/8" closed cell foam on everything. It is a ton of work, and messy, and you will slice up your fingers. It was worth it though.

[Jalves619]

Well then, . Do you know how many sq. ft of the damplifier you put in?

[bmwman91]

I believe I ordered a 160 ft^2 package of Damplifier.

The foam came from Raam audio, and I think I ordered 8 or 10 yards of it. I also bought 4 cans of the V&S spray adhesive that Raam sells.

If you want to do this, allot 2 weekends and evenings during the week. You have to take your time. The floor pan is the only section that really needs to be done over a weekend since the interior needs to be gutted. I took that opportunity to rent a carpet cleaner & refresh the carpeting outside the car.

Here are some pictures of the floor pan portion of the project. I had mounted the camera on the wall & planned to make a time-lapse video...but was too lazy!

http://bmw.e30tuner.com/my318is_pic_damplifier.php

[StereoInstaller1]

I applied Damplifier (Second Skin product) on almost every surface (except the firewall). It made a huge difference. I stripped the factory tar since the Damplifier does not stick well to it. The 318iS has less deadening than the 325, so that might be why I saw a huge improvement.

The biggest difference was made in covering the inside of the door skins.
Covering the floor pan also made a big difference. I put in 2 layers in the large central portions.

Then I put 1/8" closed cell foam on everything. It is a ton of work, and messy, and you will slice up your fingers. It was worth it though.

You didn't by chance do any spectral analysis, did you? Like before and after kind of thing?

I do know that if you did, you would have thorough data. I really appreciate that about you.

"CA&E" magazine did, in fact, do a thorough spectral analysis before and after. They pulled the interior and drove at various speeds and measured with a calibrated mic, then did 1 layer, drove again, a second layer, more analysis and then a THIRD layer, and drove again.

They spent 40+ hours a week over 2 months, thousands of dollars, added like 300 pounds to the car...for 1984, it was seriously thorough.

Hell, they showed FFT "Waterfall" plots. The mic alone was roughly $8K in those days!

What they found was that while they were confident that there was a "huge" difference, it was less than 2db at any frequency with 3 complete layers (!)

Now, here is the issue: that huge test was with the old original Dynamat, the worthless asbestos stuff. 3 layers didn't do ANYTHING...except their little expose' pissed off many of their advertisers and eventually is the main reason David Navonne gets very little published these days, even though everyone knows he is the brains behind Navonne/Clark, the "winningest team in IASCA history".

You guys do know that crap has a HUGE profit margin, right? Plus, you can charge pretty much whatever labor you want, so EVERYONE loves selling the shit...even though it really does not do much.

Trust me, I have done 3 and 4 layers of "Extreme" too. I have had to do some shit I don't believe in, we all have our jobs to do, right?

The function of "Dynamat" is to reduce resonance. It really can't remove, block or even reduce road noise, the actual air rushing over the body, the noise of the tires...it just can't. What it can do is reduce the resonances of those noises in the metal so it SEEMS quieter. It will reduce the metal from ringing, that is about all it can do.

Figure it like this: Luxury sells, right? Quiet is luxurious, right? If applying a think gooey layer of nitrile rubber and aluminum foil over the inside surface made that big a difference in noise, MBZ or BMW or Lexus would do it in a heartbeat. Those guys DO spend millions in development every year, and every twist and turn is analysed to death.

Not one of the manufacturers puts a layer of shiny goo everywhere on the inside of the sheet metal, not one. If it actually worked, believe me, they would. Look at all the other shit they have stolen from us (the mobile electronics industry) and tell me that the few dollars that stuff would cost them at the manufacturing level wouldn't be worth it.

Here is a blurb from their site:

How does Dynamat stop road noise?
As a car operates, it generates noise. This noise is caused by the transference of energy (vibration) from the internal components and from the road to the chassis of the vehicle. The chassis (doors, floors, roof etc.) transforms this vibration into audible noise. Dynamat transforms the energy (vibration) into silent energy.

Can you guys NOT see through the gobbldegook here? "Silent Energy", WTF? Read carefully, there is not one word anywhere on their site that has not been inspected thoroughly by a lawyer. The whole deal is all about protecting their insane profit margins.

Can't you guys smell the bullshit here?

I truly wish this crap worked. I LOVE a quiet car. I would gladly spend a couple of days pulling my entire interior apart, rollering until I bleed if I got even a solid 3db of reduction. Hell, even if I got 3db of road noise reduction at only 70Hz I would do it...but it really does not work, thus all the legalese, thus all the very carefully worded bullshit, thus paying the celebrity car builder who knows absolutely dick about ANYTHING acoustical (WTF, the guy has an art degree, fer chrissakes!) but it sure has lots of people fooled.

I will say this though: I have sat through MANY "Dynamat Training Seminars". They ALWAYS have provided the best lunches in the industry. We are talking really nice food, sometimes an open bar as well.

What does that tell you?

Luke

[UNHCLL]

As always, thank you Luke.
I appreciate the thorough analysis and insight.

I guess it tells me maybe it's not worth the weight/hassle/pain in the ass.

It also tells me they feed you to keep you happy & quiet. ;)

Thanks again,
Chris

[nmlss2006]

I will say one thing: I have been in an E39 with a THOROUGH dynamat-equivalent treatment. It did make a difference. I should say: there was a very large perceived difference, driving two 2002 530is back to back, one with and one without. We are, however, talking 120kg of deadening material, which I suspect explains why BMW doesn't do more of it at the factory (yes, of course there is insulation, just not THAT much of it).

[Van Westervelt]

I simply put some strips at the base of the door skins, wheel wells and the sunroof at the front. Main points where "vibration" is heard. But as Luke said, it doesnt quiet the car down really at all. I just put it there as I hated the sounds of rocks etc being thrown up and roof racks buffeting on the roof.

[StereoInstaller1]

I will say one thing: I have been in an E39 with a THOROUGH dynamat-equivalent treatment. It did make a difference. I should say: there was a very large perceived difference, driving two 2002 530is back to back, one with and one without. We are, however, talking 120kg of deadening material, which I suspect explains why BMW doesn't do more of it at the factory (yes, of course there is insulation, just not THAT much of it).

120Kg? DAMN!

You did bring up a great point: little strips will also reduce resonances pretty dramatically. Think of the waves of energy travelling through the metal (literally through, not "passing through") and what placement will disrupt that wave. You can achieve much of that same effect of seeming to reduce road noise with just a couple of sheets.

BTW: all of the sound damping that car manufacturers use today is Nitrile: they basically quit using the worthless asphalt crap.

BTW: one of the reasons I design the boxes the way I do it to reduce noise coming through the trunk into the car.

One of these days I will have a properly calibrated mic and will be able to do FFT analysis. There has to be a way to actually reduce noise, right?

[bimmerteck]

You didn't by chance do any spectral analysis, did you? Like before and after kind of thing?

Luke

I actually have, Dynamat extreme made less than a 3db on average difference in the noise floor of my 1990 VW jetta while traveling @70mph down the interstate. I had 2 layers covering every inch of the interior and the doors were removed and coated in 1/8" of a liquid damping product. The difference was not as much as I hoped for but I didn't have a dime in the any of the products used. I will say that anyone who got into the jetta who knew VWs asked why mine seemed nicer. (shutting the doors on that treated jetta sounded like shutting the doors my my grandfather's s500 with a solid thud instead of a light click.

I haven't had another car worth treating, and doubt I ever will, but I will tell you an extra door seal added to the doors and a much less aggressive tire tread both made bigger difference in the interior noise levels. ;)

[nmlss2006]

Luke,
agreed on the nitrile and yes, 120kg is significant. The mandate was clear, it was called 'I want this thing to be quieter, do what you must'. The amount of money spent was .. material.
As to actually reduce noise, sure: what he did actually reduced noise, I believe. The problem is, in order to do it, you have to separate the resonating layer (metal) from the air inside. Which means that the layer must be continuous and not have ANY gaps. It gets difficult and expensive.

[bmwman91]

Fudge, I had a good response typed and I accidentally closed the tab when I was finding supporting info. I don't feel like retyping it.

For the most part I agree with Luke. The sound deadening industry is full of BS and fantastical claims. There are very real improvements that can be made through mass-loading resonant surfaces, but not to the extent that people think, nor by the mechanisms advertised.

Deadening is usually advertised as working by converting the motion of panels into heat in the tacky rubber/tar material. While this is true, it is probably to a lower extent than the manufacturers would have you believe. In reality, the mass-loading of resonant panels serves to move the resonance frequency lower, not eliminate the acoustical energy. The human ear is most sensitive to frequencies of ~250Hz-5kHz. If you can mass-load a panel and shift its resonance from say 300Hz to 150Hz, even if the panel still radiates the same amount of acoustical energy, our ears will hear it as being distinctly quieter. That is the whole trick with mass loading...move the resonance out of the voice-band that our ears and brains are wired to pick up on most.

Truly, it probably is a colossal waste to cover 100% of the surfaces. I would be willing to be that covering the middle 20% of large plane areas will make 80% of the perceived improvement, while covering up the remaining 80% of the area will only make a 20% difference. It is the good old law of diminishing returns.

I think that an effective method would be to put different amounts of mass on similar sheet metal panels. That way they all resonate at different frequencies, as opposed to all resonating at similar ones. Spreading the resonant energy across multiple frequencies will come off as a lot less annoying than having them all localized into a single tone.

Is the stuff I put in really any better than the BMW tar? I have no idea. I added a lot more mass to the middles of panels than BMW did, so I fully expect that the resonance frequencies got moved a lot lower, and this it seems quieter since I am less sensitive to them. The car is most certainly more pleasant to ride in now, and even my fiancee commented on it (if SHE notices, then you KNOW the difference is real).

So again, you do not need as much material as sellers would have you believe, nor does it actually "remove" acoustical energy as heat to any major extent. You could probably glue steel plates to the centers of the panels and have a very similar effect. I just prefer the Damplifier stuff since it is relatively easy to apply, doesn't stink and can be removed someday, if I need to. It also seems to hold-up very well to temperature extremes, which is good because I do not want it falling off of my sunroof or hood!

Luke, do you happen to have the spectrograms from your measurements? I would love to see the data. I never measured anything. "It's all in my head," as they say.