Basic sound deadening for the Riviera

My buddy hooked me up with some dyanmat a while back when I had a subwoofer in my trunk. I put a few square feet on my trunk lid but later ended up selling the sub in order to attend a Tool concert . Now I am left with several square feet of dynamat. Where do you guys think are the best spots among the riv to put it to get the best reduction in road noise?

Albert should be able to answer that question from experience. He did a lot of research on it and did his car up.
Might want to get his attention for some input.

rivman96 wrote:

My buddy hooked me up with some dyanmat a while back when I had a subwoofer in my trunk. I put a few square feet on my trunk lid but later ended up selling the sub in order to attend a Tool concert . Now I am left with several square feet of dynamat. Where do you guys think are the best spots among the riv to put it to get the best reduction in road noise?

I think I'd like to know what you mean by road noise. Not being flippant, it's just that what some think is road noise is really self-noise from the car's systems (exhaust, engine, drivetrain) and what others think is road noise is wind rush (Riv has a chronic wind rush noise above about 45 MPH that there's not much that can be done about it) and what still others think is road noise is tire howling, which would change depending on what tires you decide to run.

The other thing is different people's hearing differs somewhat; different people find different sound frequencies to be either inaudible or intolerable.

So where I can be most helpful to you depends on what you can tell me about what noise you want to get rid of.

Self noise from the car's systems: for exhaust and engine, this would typically be noise you can hear when you have started the car and it is just sitting. Have to measure with engine on and engine off. Typically a stock Riv is so quiet that although there is noise from the running engine some people can not hear it at all and for most it is not an issue. Then rev the engine through 4000 RPM or so. Is there exhaust noise? Something loose on or wrong with the engine so as to rattle, whine or squeak? Bottom line: So if your Riv is making noise while idling in neutral or park, you have some work to do with heat shields, as well as with motor and transmission mounts, unless there is a major mechanical systems problem causing your engine to vibrate or lope excessively. If it's noise while revving, you may be talking exhaust noise or a different mechanical issue. Some of this noise has to be dealt with by mechanical changes. If you have exhaust noise at idle, question is is it on purpose or do you have a hole in a muffler? If a hole, fix it. If on purpose, then it can be damped but be aware that it can only be damped so much.

Noises while moving: this is typically transmission/transaxle/tires, wind rush, wind whistle (different from wind rush), ,maybe exhaust, or rattles/squeaks in the vehicle. some of these can be damped with a layer of eDead, Dynamat or what have you on the floor pan in the passenger cabin and trunk. A layer of mass loaded vinyl on a fibre pad installed under the rear seat will help as well.

So when you tell me more about the noise you are going after then I can tell you how to dampen it.

Finally, remember it's a moving vehicle and to a degree you need to hear what it is doing and what is going on outside of it, for safety reasons. So after I get vehicle self-noise and moving noise below about 70 dB I think I'm done.

Albertj

I certainly don't mind the sound of my engine and exhaust, and nothing to my knowledge can be done about wind-noise. As far as rattling, etc. I consider my riv to be quite healthy, so I figure I'm aiming to reduce tire howl. Would I be correct in stating that aside from wind noise, tire-howl produces the most noise at highway speeds?

Another sound deadening resource:

http://cascadeaudio.com/car_noise_control/index.htm

Instructions and materials.

Albertj

I'm going lowbuck on my build with

http://www.frostking.com/Lowes/FoamFoilDuctInsulation.htm
I'll post results.

jonly wrote:

I'm going lowbuck on my build with

http://www.frostking.com/Lowes/FoamFoilDuctInsulation.htm
I'll post results.

Looks like that will help with high frequency noise, sort of, and heat insulation, but not with panel resonances (that's what Dynamat and similar mastics are for).

I made up a heat insulation material for a Volvo I used to own, using Radio Shack fireproof fiberglas batting (they don't sell it anymore) and aluminum foil that I attached to it with 3M spray on trim glue. Worked *very* well.

Albertj

mcmaster carr also has really cheap sound suppression material.
i've used the 1" uncoated stuff before and its easy to work with and very sticky.

http://www.mcmaster.com/#sound-absorbers/=9rk1ig

albertj wrote:

Looks like that will help with high frequency noise, sort of, and heat insulation, but not with panel resonances (that's what Dynamat and similar mastics are for).



Albertj

valid point. here's another resource that someone at the hamb linked to
http://www.sounddeadenershowdown.com/cgi-bin/index.cgi

jonly wrote:

albertj wrote:

Looks like that will help with high frequency noise, sort of, and heat insulation, but not with panel resonances (that's what Dynamat and similar mastics are for).



Albertj

valid point. here's another resource that someone at the hamb linked to
http://www.sounddeadenershowdown.com/cgi-bin/index.cgi

I've used materials from Sounddeadenershowdown - the guy knows what he's talking about and the quality is what he says it is. I used some of the massloaded vinyl barrier along with some commerical fire-spec carpet padding I had around to get rid of the exxaust/road nois that comes from under the rear seat. Used butcher paper to cut a pattern (newspaper will work too) and then transferred that cutout to the vinyl, which cuts just fine with those forged steel dressmaker scissors (most of the stainless stamped ones they sell nowadays are too light and too dull). Then I applied the carpet passing tot he underside and then installed it. I'd say it knocked 5-8dB off the noise in the cabin doing that alone (measured with my cheapo sound level meter but don't remember the number).

And he's right about vibration dampers like Dynamat. Cover the panel about 25 to 30% then use the foams/padding to soak up the sound that's not panel resonance. What worked for me in the trunk of the Riv was using the handle end of a screwdriver to drum on the panels and putting eDead on the drummy areas. Then apply extra fiber padding to the underside of the trunk liner carpet.

We will see how your project goes.

Albertj

Has anybody tried that lizard skin product?

How does it compare to the dynamat type products?

What does it cost versus the dynamat stuff?

VegasScott

Lizardskin?

At $160 plus application equipment to cover 50 sq ft only?

I have not tried it so I can not say, here are posts from folks who have tried it::

http://www.jalopyjournal.com/forum/archive/index.php/t-132738.html
http://www.nastyz28.com/forum/archive/index.php/t-201614.html
http://lizardskin.com/pages/ceramic.php

Albertj

albertj wrote:

Lizardskin?

At $160 plus application equipment to cover 50 sq ft only?


Albertj

I have no point of reference if that is a good price or expensive. I am fortunate to own all the necessary equipment to spray the goop on.

How does this compare with Dynamat or the edead stuff you used?

Thanks!
VegasScott

VegasScott wrote:

albertj wrote:

Lizardskin?

At $160 plus application equipment to cover 50 sq ft only?


Albertj

I have no point of reference if that is a good price or expensive. I am fortunate to own all the necessary equipment to spray the goop on.

How does this compare with Dynamat or the edead stuff you used?

Thanks!
VegasScott

I will start off by saying that what I think about this probably should not matter to you; what matters probably is just how much of the car you want to coat and what results you want.

To get rid of sound resonance you have to increase the mass of the panels, that is what the mastic/butyl coated aluminum foil sheets are intended to so. To get rid of sound transmission you have to do a combination of reflecting sound away and damping its transmission, usually by turning the sound into heat (which is what the mass loaded vinyl/expanded foam, or lead (yes lead metal) foil/foam sandwich sheets do. My understanding is the ceramic spray is intended primarily to insulate from and reflect away heat, and as a side effect they add some mass which cuts transmission and resonance. I'd have to see sound meter readings of before/after application to comment further.

The other observation is that how happy you are depends on what you set out to achieve. I set out to get the ambient noise in the car below "office" levels. There are a *lot* of ways to improve on what I did and they really would not cost all that much. For instance, a big improvement over what I did would be to use the mass loaded vinyl/foam sandwich to replace the fiber padding under the trunk liner, and pull the passenger compartment carpet out and replace its fiber padding with the same vinyl.foam stuff (leaving its glued/molded on foam in place)
Another would be to use a spray mastic, some sort of tarry stuff, followed by sand (yeah, cleaned play sand the white or the brown stuff) and recovered with more mastic or the ceramic insulating spray, all over the underside of floor pan and trunk (have to drop gas tank to reach parts of that).

Another thing is you kind of need to buy or borrow your own sound meter (radio shack sell them for under $100) to tell what's going on. You may find that your environment is so noisy that you can't tell how much fo the car's sound you've damped out.

Albertj

Albert, yet another great write up with informative info! Thanks, but I may have not been clear on my question because I didn't see what I was looking for. I was asking about the costs of both products for that 50sq ft area, and if anyone has tried both products. I saw some posts on another car forum that I frequent, and heard some good results from LizardSkin. Then again, I don't know if some of these guys have tried anything else. The male ego is a weird thing. Those guys could have bought this stuff, made a complete freakin mess, and would NEVER admit to it.

VegasScott

VegasScott wrote:

Albert, yet another great write up with informative info! Thanks, but I may have not been clear on my question because I didn't see what I was looking for. I was asking about the costs of both products for that 50sq ft area, and if anyone has tried both products. I saw some posts on another car forum that I frequent, and heard some good results from LizardSkin. Then again, I don't know if some of these guys have tried anything else. The male ego is a weird thing. Those guys could have bought this stuff, made a complete freakin mess, and would NEVER admit to it.

VegasScott

question: how are you going to apply"neatly" lizard skin in the nooks and crevices of the car? those hard to reach places? dynamat and other "stick on" products are the only way to go.

robotennis61 wrote:

question: how are you going to apply"neatly" lizard skin in the nooks and crevices of the car? those hard to reach places? dynamat and other "stick on" products are the only way to go.

Well, sound deadening isn't usually applied to nooks and crannies. Its usually only applied to the large flat surface that tend to vibrate. But regardless, there is no way a mat type product will conform AS EASILY to a complex curved surface as a spray on sound deadener. I don't know how much I want to spray crap all over my car when I don't know how well it works. At least with the dynamat sheets, I can use a heat gun and peel them off if I don't like it.

As for spraying into tight quarters, I've got lots of experience doing that, while painting cars. More specifically painting the inside of a trunk on over a half dozen vintage Volkswagen Beetles!

VegasScott

wow! looks like youve covered all the bases!

Not yet, but I'm doing my "homework" before I fork over some more of my hard earned cash for this type of product.

Thanks for the help guys!

This is a great forum!

VegasScott

VegasScott wrote:

Albert, yet another great write up with informative info! Thanks, but I may have not been clear on my question because I didn't see what I was looking for. I was asking about the costs of both products for that 50sq ft area, and if anyone has tried both products. I saw some posts on another car forum that I frequent, and heard some good results from LizardSkin. Then again, I don't know if some of these guys have tried anything else. The male ego is a weird thing. Those guys could have bought this stuff, made a complete freakin mess, and would NEVER admit to it.

VegasScott

Apologies. Thanks for pointing out I missed the question. Answer: eDead costs $1/sf for 40 mil and $2/sf for 80 mil. See http://www.edesignaudio.com/index.php?cPath=1_24. You can get it a little cheaper on eBay. So 50 sf of eDead is about 1/3 the price of similar coverage of that spray you were talking about.

I guess the thing I was responding to is that spray vs. eDead sheet, they do different things, really, and so aren't comparable. Sort of. The other thing I didn't do was to talk about where a dollar spent would have a certain effect. That is, you can compare price per s/f. eDead is a buck and the spray is 3. You can not compare what they do. eDead loads body panels with mass and cuts resonances by being soft and absorbing the sound energy somewhat. The spray insulates from heat and cuts resonances by making the panels thicker without adding much mass. I don't know if the spray stays soft after application.

As far as my car is concerned, the biggest noise now is wind rush. The wind rush is not so loud you can't enjoy the factory stereo or have a conversation, but it is the loudest sound in the car when running on the highway at present, with summer tires on. With snows (Goodyear UltraGrip Ice) on the snow tire whine is the loudest sound. What I did: I put eDead on the reverberating spots in the trunk and under the back seat including the sill under the front of the rear seat bolster. I used somewhat less than one roll of eDead for this. I made a mat of some fiber auto-type carpet padding and mass loaded vinyl to fit under the rear seat. I added some of the same fiber-type padding to the trunk liner (including the Masonite board on the rear seat back) and re-installed it.

Ummm.... comparing eDead to your spray...

- eDead will stay in place for the range of automotive cabin temperatures but isn't really heat insulation.

- Your spray is primarily heat insulation and has the side-effect of some sound deadening.

- Nobody is commenting on whether the smell of the spray we're talking about is noxious. That is, do you really want to spray that stuff inside a car cabin? I have no idea. Need to read the label and the MSDS.

Did you see the earlier discussion about this at https://rivperformance.editboard.com/interior-f20/basic-sound-deadening-for-the-riviera-t6249-15.htm - if so sorry for repeating and if not, well you might want to.

If I had the equipment, the time and the interest I'd consider the following: -- if I could control the odors then I'd remove the interior and spray in a mastic of some sort, including in the doors, the roof (removed headliner) and rear quarter panels. and then while it is wet put sand on it all over. Probably common auto rustproofing or body sound deadener like the 3M Underseal stuff. Then I'd spray something else on to hold the sand in place and interfere with teh odor from the Underseal. Probably an acrylic auto paint, one of the low VOC cyanoacrylates. Then add a foam/mass loaded vinyl or foam/lead sheet to underneath the carpet/trunk mat/rear seat. I'd also fill the A pillars with expanding foam. Then reinstall it all.

There would be a gas mileage penalty, it would come from increased weight/inertia, probably no real effect on highway gas mileage (that's wind drag, wheel bearing and tire friction losses) but you'd see it in the city/suburban stop & go.

Your further thoughts?

Albertj

I'm just not sure if I want to spray goop all over my car if its efficacy is in question. I would hate to spray it, be fully committed to and find out that it sucks. Then I'm stuck with the laborious task of having to clean all that sh*t off my car and start over with a dynamat type product.

I know there are several different applications they make. One is for sound deadening only, and the other is for sound deadening and heat shield.

I've used dynamat before on vintage Volkswagen and it really worked well.

Thanks again Albert!

VegasScott

VegasScott wrote:

I'm just not sure if I want to spray goop all over my car if its efficacy is in question. I would hate to spray it, be fully committed to and find out that it sucks. Then I'm stuck with the laborious task of having to clean all that sh*t off my car and start over with a dynamat type product.

I know there are several different applications they make. One is for sound deadening only, and the other is for sound deadening and heat shield.

I've used dynamat before on vintage Volkswagen and it really worked well.

Thanks again Albert!

VegasScott

I agree with not spraying ineffective goop.

I guess the thing is the ceramic spray will attenuate sound but not as well as a mastic (the tar like stuff) that's loaded with sand. Dynamat is butyl loaded with a filler - it's not exactly sand but pretty much.

Dynamat will not insulate against sound passing thru as well as a mass loaded vinyl/foam or lead foil/foam sandwich. HOWEVER it does get rid of spurious resonances so well that the overall effect (as you know form your own experience) is pretty quieting. Also, given the realities of spraying stuff, Dynamat will probably weigh less for a given application.

I am told the best attenuation of resonance is by spraying on undercoating and then using a sandblasting rig (at relatively low pressure) to spray fine sand onto the wet undercoat. Then coat again. This must be done on sound non-rusty metal or else the reust and moisture just get trapped in which causes bigger problems. I am told the best attenuation of sound transmission (per unit volume) is a closed-cell-foam/lead foil/closed cell foam sandwich--getting the lead foil under current regulations is possible, actually.

Albertj

Check out secondskinaudio.com. great company with great customer service, or give thim a call. The have the vibration dampener which is better than dynamat, also the mass loaded vinyl and the closed cell foam. use the closed cell foam(they call it overkill) on top of the vibration dampener(they call it damplifier) for the doors and use the mass loaded vinyl(they call it luxury liner) on top of the damplifier for the floors/trunk. That is what I am curently doing I will write up a review once done but just the damplifier helps out already. The damplifier is equal to dynamat and the damplifier pro is way better than dynamat.

They are much cheaper compared to dynamat. I bought the overkill, luxury liner, and damplifier for about the same price as just dynamat.

And if you do want to spray they have that too as well as spray for heat too.

Here's an idea (although slightly off topic)...

Here in Vegas, we all have these cheap ass, "aluminum can thin" garage doors. I wonder if you could use that thermal lizard skin stuff to coat the backside of the garage door? It would make the garage door sound a little more solid, and potentially could help insulate the door a bit better.

VegasScott