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Thread: Underbody sound deadening - older truck

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    Underbody sound deadening - older truck

    Looking for the best option for underbody sound deadening. I have an old 4runner and the inside is stripped and linexed, so a mat/material that lays down won't work. I can put something inside the rear wheel wells, inside of the front wheel wells, and on the firewall behind the dash as it is all torn apart already. The only other place I can put sound deadening is on the underbody, which wouldn't be too bad b/c there isn't much under there other than the tranny and transfer case.

    I'm not looking for something that is going to be a silent ride by any means, but reducing in cabin noise would be great. What are your thoughts for the best options on a project like this? I am not just talking about doing it, this project will happen and I can post pics/progress if you all want it.

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    MySQL Error soundman98's Avatar
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    i think the spray-on undercoating is going to be your best bet. i don't believe most sound deadeners(spray-in, or mat) are durable enough for under-car usage..

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    MySQL Error soundman98's Avatar
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    i saw the part about undercoating, though, i think it might mean below other layers of sound deadening inside the car-- there is no reference to exterior usage...

    maybe try pming ant(owner of diyma, and second skin), or emailing the second skin store?

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    I think I will give them a call tomorrow and see what they say about the project I have going and I'm sure they will give me some good input.

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    Car Audio Moderator durwood's Avatar
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    To be honest here, to prevent airborn noise transmission, the only way is to block it so that is attenuated. This would require a heavy dense mat material like rubber, vinyl or lead, or aluminum. The blocker materials would have to be ~1/8" to get decent blocking/attenuation at lower frequencies and it has to float above the floor with a closed cell foam so that there is dead space between the sheet metal and the blocker. Otherwise the, noise will transmit right into the new material. Anything else is really a waste of your time and money. Mass loaded vinyl with is the same stuff used to block the noise from your firewall, except the use a recycled cotton material to float the MLV away from the sheet metal.

    Second Skin was built around taking advantage of unknowing consumers and other borrowing ideas from competitors products, and later sold by the owner to another unknowing person. I guess that is the how many marketing based businesses work though in a competitive market.

    If you can't lay a mat down, forget it. If you don't believe me contact Rudy @ sounddeadenershowdown he should be honest with you and seems to be one of the only companies that actually know what is and isn't possible. Cascade is also another more trustworthy company.
    Last edited by durwood; 06-06-2011 at 03:49 PM.

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    Thank you very much for the info, I appreciate it and believe you. Is there a thread/sticky that is solely on sound deadening, so I can learn some things about it.

    At this point, would it be worth it to have kind of sound deadening in my wheel wells in the rear (inside of truck) or the two doors on the truck? This truck is torn down 100% inside and I pretty much only have to drop the tranny and gas tank to have the entire undercarriage exposed (not a lot work). I am trying to keep the inside flooring with the linex that is on it b/c it is great, nearly indestructible, and very easy to clean.

    You had mentioned transmission noise, what about your typical road and wind noise? I know I can't achieve a luxury car dead quiet sound, but definitely looking to try and knock down some noise.

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    Car Audio Moderator durwood's Avatar
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    What is "road noise" Where does road noise come from?

    Tires contacting the pavement. That is pretty much it. There is the friction, the sound from when your tire hits bumps, etc. The wheel wells really concentrate it like a waveguide or horn, making it worse. I have a feeling you have knobby tires on your truck too.

    Wind noise is slightly different but can be remedied by making sure your seals make good seals. Boxy vehicles will still suffer, but it's all about blocking wind and "road" noise.

    Exhaust is also airborne noise, it is not about anything striking the panels unless your exhaust rattles.

    Structural noise from the road, exhaust and engine are isolated by the rubber tires, shock absorbers, various rubber bushings on the suspension and motor mounts.

    What do you see in these pictures? Blockers


    http://www.fhwa.dot.gov/environment/...n/design05.cfm

    http://www.fhwa.dot.gov/environment/...n/design03.cfm

    Read up on the difference between STC vs NRC. Road noise which is mostly lower in frequency is hard to absorb, therefore you must block it.

    http://www.acoustics.com/tutorial01/slide1.html

    http://www.stcratings.com/

    Closed cell foam and MLV are waterproof, they do not absorb water, but I don't know how you plan to use it if you like the look of painted metal on the inside.



    Closed cell foam and MLV are waterproof, they do not absorb water, but I don't know how you plan to use it if you like the look of painted metal on the inside.
    Last edited by durwood; 06-06-2011 at 09:03 PM.

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    It is for functionality on the interior, not necessarily looks with the linexed interior. Thanks again for the info. I will read through it.
    Last edited by live4soccer7; 06-07-2011 at 02:13 AM.

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    I read through the majority of the info. Good stuff and a lot of it there.

    So, if I were to down sound deadening materials on the metal on the inside what would be the best way to go? What would the layers be?

    Would this be the correct order?: floor, closed cell foam, blocker

    Is there anything else in there, that should be added? Also what brands do you recommend for these materials?

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