Questions about sound deadner in doors

[bosephus]

I have a 61 that I'm working on.FatMat is purchased and doors are gutted.Question is,where do you apply the fat mat? Inner side of outer door skin?Just the removable door panel? 100 percent coverage? How did you do yours and did it work? HELP!
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[vin63]

Did you order the traditional Fat Mat or the butyl-based product?

I usually just put a 3x12 inch strip of the butyl damper on the inside of the door skin and a similar size (if space allows) on the inside of the removeable door panel. This cuts down on a significant amount of panel vibration and resonance.

[bosephus]

I bought the thick RATTLETRAP version. That's good news that full coverage isn't necessary! Seems like a PITA to completely cover the inner door.
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[ChuckW]

I did Dyna Mat in mine. I only covered the center area on the inside door panel inside the door as I worried about water soaking if I installed it on the inside of the outer door skin....? I also did the removable panel... huge differance in the doors! I like it!!

[ChuckW]

I also sprayed 3M undercoating inside the door on the areas that the Dynamat did not cover! (fyi)

[joedoh]

sounds travel best through air, transmission through solids is by resonance, meaning the sound waves on one side vibrate the solid and that vibration causes the sound you hear on the other. there is a frequency inherent with solids and based on mass that requires the smallest input and has the largest output, and this is called the resonant frequency, the most sympathetic frequency to vibration.

with mat (rubber or asphalt) its about adding mass to lower the resonant frequency. lower frequencies take a lot more power to resonate, anyone who has ever bought a subwoofer amplifier will tell you the same thing, so by lowering the resonant frequency it takes more power (noise on the outside) to be loud (noise on the inside). Also, the lower frequencies arent as intrusive as higher frequencies.

so adding any at all to a large flat panel will damp the resonance. you dont need to coat the entire panel, you arent sealing anything.

and for the same reason, you dont need multiple layers, because its a diminishing return. if you lower the resonant frequency with the first application it will be your largest gain, extra layers will just spend money for much smaller results.

So to recap, if you have large flat panels, add some mass. Some noise will be inherent from having an all metal cab, it would be good to cover the steel with some cloth, but damping mat will help a LOT.

[bosephus]

Thanks for all the input. Love this site!
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