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Hi Frosty,

MLV = mass-loaded vinyl
CLD = constrained-layer dampening
CCF = closed-cell foam

The best sound deadening products have high mass/area for broad-band attenuation down to low frequencies, and high loss factor for high dampening. IIR rubber (essentially butyl) is great for this. Note that low mass/volume can be fixed with high thickness. Btw the OEM often puts a patch of mass with dampening in the center of the door to get a nice 40-ish Hz "thud" when the door closes. I believed Shien posted a photo that showed an example of that.

Foaming a material is unhelpful for sound attenuation because the cells are filled with air, and air has low mass/volume (1.18kg/m^3.)

Incidentally, maybe the most effective noise-deadening material on the planet is lead. And of course, the stuff is heavy, by intention. Some OEMs use more than 100lb of sound-deadening materials in their luxury vehicles. About mileage: fuel economy goes very roughly as the reciprocal square root of mass, so if we add 40lb of mass to a 4,500lb Sienna, we should expect very roughly a 0.5% decrease in fuel economy.

HTH,
mapirc
 

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I cheap out with my 06 LE. I use a pair of squeeze type ear "dickies" then slap on my Bose noise cancelling headset. I have to be aware of local state laws waering headsets while driving. One day though I would like to take my panels off and deaden with appropriate materials.
 

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Hi Paul - I own those (QC3) too (in fact, I know the people who designed it.) Yes, to the precaution about local ordinances, and ANR headphones reduce audibility of all exterior sound, so needful audio cues while driving will be suppressed. Then we have the basic encumbrance of wearing headphones. I agree best to treat the vehicle...
 
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