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Thread: Cork as sound deadener? Recommend other materials to absorb noise.

  1. #11
    FLAC
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    After doing a bit more indepth research and looking at sound absorption coefficients for materials, Ive decided to get a 100sqft 3 mil roll of fibrous carpet underlay (they call it jute in the above link for civicforums). It's supposed to be good at absorbing high and mid range frequencies. As for the low frequencies...thats what the Resisto is for. I plan on using about 4 layers of this stuff (its pretty thin) and replacing the foam underlay which I currently have on my floors. Maybe stuff some of it in the dash if I have leftovers. I hope this works.

  2. #12
    Car Audio Moderator durwood's Avatar
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    Crap I wish I would have seen this earlier.

    You need a blocker material. Not an absorber. Abosorbers are good for high frequencies, but what you are trying to do is limit the amount of road noise coming into the vehicle which is all lower frequencies. That carpet underlay is a high frequency absorber, not a low frequency blocker.

    Study the differences between NRC and STC-they are different.

    Mass Loaded Vinyl (MLV) is a good blocker and probably the best material you will find for the money. Deadener is good for reducing vibrations of flat unconvoluted panels-but it also lowers the resonant frequency of the panel. It is not a good blocker/barrier. The foil helps block noise, but it's much more costly to line your entire vehicle with multiple layers of it.

    http://www.noisedead.com/ John is a good guy and will help you out.

    Second skin also has their luxury liner pro
    You might be able to find commerical places that sell it as well.

  3. #13
    FLAC
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    Well, I already have the wheel wells coated in about 1/2 inch of asphalt undercoating. I plan on doing the rest of my underbody with undercoating as well, so that should act as the low frequency blocker. I dont really want to tear apart my whole interior to cover everything with sticky mat based deadener so right now I'm just ripping open small areas to be able to stuff the jute sound absorber underneat my carpetting.

    Is mass loaded vinyl a low frequency absorber? Could I just stick sheets of that in between the jute?

    Right now I think most of the noise is from the engine and from the tires vibrating the whole metal frame. Strangely, the car feels more quiet at highway speeds then it does at low speeds.

  4. #14
    FLAC greatwhite's Avatar
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    Try this:

    with the car a various speeds (and no traffic!) slip the transmission into neutral and let the engine idle. The noise you hear is "road noise" and possibly interior rattles. Whatch your speed and rpm before you slip it back into gear please!

    Now at idle in park, slowly rev the engine up to driving rpm (around 3,000 or so) this is engine noise (well, exhaust noise is in there too). Don't get too crazy revving the engine in park either!

    Now that you know which noise is which and where it is comming from, you can start attacking each source and retest the same way when you think you have it. You want to attack the the noisiest offfender first to get you best bang for the buck (IE: floor wheel wells, firewall, trunk, etc)

    Keep in mind, this is just a low buck way of finding noise.

    If you start laying on the dynamat (or whatever you choose, that McMaster-Carr mineralized vinyl sounds interesting) and notice a "tar like" pad on the panels, leave it there. That is the OE noise dampers and is probably there because an engineer found that was the best place for it to reduce noise during NVH testing.

    Cheers.
    For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return.
    Leonardo Da Vinci

  5. #15
    Maximum Bitrate Woofnstuff's Avatar
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    what do you drive a battle tank? how much weight are you adding,
    i was thinking of doing this sort of thing to my car but was concerned about the additional weight.

  6. #16
    FLAC greatwhite's Avatar
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    I'm looking at adding expanding foam to the vehicles open cavities. The factory already fills most of the voids with the stuff, I'm just going to finish it off..........

    Then I'll look at dampening (with a mat product, haven't decided yet but second skin is looking good) the doors first, then the wheel well area's, the trunk and finally the cabin floor area's.
    For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return.
    Leonardo Da Vinci

  7. #17
    Car Audio Moderator durwood's Avatar
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    CLD or deadener materials are NOT blockers.The aluminum backing has some blocking ability but it would take several layers to do any good. Why do you see people pile it on layer after layer? Because it doesn't do a good job of blocking. You are never going to absorb 50-250Hz frequencies from tire/road noise and exhaust with deadener OR undercoating. All you are doing is changing the resonant frequency of the panel and actually LOWERING it into the same frequency band as the offending noise. This will make it worse.

    Absorbing DOES NOT equal Blocking.

    Look up "Mass loaded Vinyl", its the next best thing to lead at a 1/4 of the cost. In order for it to be effective, you need to cover the entire floor with it and use aluminum tape to seal it at the edges so that sound does not escape and become airborne.

    Take a look at your firewall, it usually covered in this stuff (MLV) for a reason.

    Look at it like this:

    Noise on the outside trying to get in ->use a blocker
    Noise on the inside out of control ->use an absorber
    Flat panel materials creating extra unwanted harmonics or frequencies -> use deadener
    Panels rattling against each other ->use a closed cell foam gasket to prevent rattling

    NRC vs STC

  8. #18
    FLAC
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    Yikes, MLV sure is expensive:

    http://cgi.ebay.ca/AudioSeal-Mass-Lo...QQcmdZViewItem

    I suppose my car isnt actually THAT noisy...I'm just going to use up my roll of jute and call it a day. I can see how this hobby is going to be a money pit.

    I guess plan B would be to save up for a mercedes.

  9. #19
    Car Audio Moderator durwood's Avatar
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    Quote Originally Posted by nobb View Post
    Yikes, MLV sure is expensive:

    http://cgi.ebay.ca/AudioSeal-Mass-Lo...QQcmdZViewItem

    I suppose my car isnt actually THAT noisy...I'm just going to use up my roll of jute and call it a day. I can see how this hobby is going to be a money pit.

    I guess plan B would be to save up for a mercedes.
    That roll is 30ft of it, or 135 sqft. What do you drive? A bus? If that's the only place you can buy it, use what you need, sell the rest-but if you can find another source I'm sure you can buy less-I already gave you two names of companies that sell it, now it just depends on if they will ship to Canada.

    Seriously, IMO why waste your money on something that doesn't really do much instead of saving up a few more bucks and buying the stuff that does the job right? If the stuff is capable of reducing airborne roadnoise by 10db, how much amp power or acoustic SPL would you need to get that kind of gain above the noisefloor?

    Glass blocks low frequenices at about 22dB and the sheet metal in the car blocks at about 12dB IIRC, so all you need to do is lower the noisefloor by 10dB before the glass becomes the limiting factor.

  10. #20
    Maximum Bitrate Megalomaniac's Avatar
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    Quote Originally Posted by durwood View Post
    That roll is 30ft of it, or 135 sqft. What do you drive? A bus? If that's the only place you can buy it, use what you need, sell the rest-but if you can find another source I'm sure you can buy less-I already gave you two names of companies that sell it, now it just depends on if they will ship to Canada.

    Seriously, IMO why waste your money on something that doesn't really do much instead of saving up a few more bucks and buying the stuff that does the job right? If the stuff is capable of reducing airborne roadnoise by 10db, how much amp power or acoustic SPL would you need to get that kind of gain above the noisefloor?

    Glass blocks low frequenices at about 22dB and the sheet metal in the car blocks at about 12dB IIRC, so all you need to do is lower the noisefloor by 10dB before the glass becomes the limiting factor.
    durwood id like to add to your post earlier about the Luxuruy Liner. I suggest if you do use it to be sure to buy that foil tape to seal that liner to the floor. otherwise the sound will "escape" and that barrier wont be as wonderful as you'd imagine.

    many steps to deadening. Idea is to put different materials(densitys) to block certain frequencies.

    on the floor id probably layer the floor with Damplifier(mat), then go over it with spectrum(liquid deadener), let it cure overnight, then the luxury liner(and tape the edges off with that alloy tape to seal), finally if i cant fit my stock carpet back id recarpet the whole car....I know its extreme but if you really want that "luxury comfort" you got to make sacrifices to do so.


    www.secondskinaudio.com <--where i get my deadening
    screen name here use to be MegaloRESE15"

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