Author Topic: MASS LOADED VERSUS FOAM  (Read 5447 times)

kusojiji

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MASS LOADED VERSUS FOAM
« on: June 20, 2007, 09:17:17 AM »
I'm in the process of sound proofing my car.  I know about the "Dynamat" type materials but am confused about their application.  Isn't the function of these dense materials to prevent vibration?  If so, then applying this stuff over 100% of a surface is not necessary, right?  My opinion is that if the metal inner door surface has a bend or curve, then it is inherently stiff.  The material should only be applied to large, flat surfaces such as the outer door skin.

One concern that I have with these dense materials is weight.  My car is lightweight and has no power, the trade-off being good gas mileage and noise.  I've installed some of the "Dynamat" type materials on the outer door skins and have noticed a good reduction in road noise and the noise from adjacent vehicles.  I've only applied enough to stop the ringing sound when I tap on the door.

My next step is to apply a foam type material between the door panel and inner door metal surface to absorb / block sound.  I like the foam as it is lightweight in comparison to the denser stuff.  I think that the foam needs to go over 100% of the surface to be effective.

Am I on the right track or in left field?  I do not believe that just because everyone else is doing it or a manufacturer recommends something is necessarily correct.  Of course a manufacturer is going to recommend 100% coverage or more is better!

Any info would be appreciated!

johnbergstromslc

  • Guest
Re: MASS LOADED VERSUS FOAM
« Reply #1 on: June 23, 2007, 09:49:58 PM »
Well, the physics of vibrating sheet metal (with low damping) differ from that of drywall and wood and is beyond the focus of this forum, but my vote is for 100% coverage.  You want to increase the density of the panels and decrease the vibration.  Any metal left bare compromises this. 

If you're concerned about weight, use a thinner Dynamat sheet, or use a viscoelastic 'paint-on' coating.  It runs 60 bucks/gallon, but 2 gallons is usually enough to do the whole car (applied at the thickness of the metal) and adds less than 20 pounds to the weight.  An extra 20 lb on a 3000 lb car won't make a dent in mileage - equivalent to having an extra 3 gallons of gas in the tank.

Check out this page for the 'paint-on' stuff:

http://quietcoat.stores.yahoo.net/

       

bjnash

  • Guest
Re: MASS LOADED VERSUS FOAM
« Reply #2 on: June 23, 2007, 10:13:56 PM »
Well, the physics of vibrating sheet metal (with low damping) differ from that of drywall and wood and is beyond the focus of this forum, but my vote is for 100% coverage.  You want to increase the density of the panels and decrease the vibration.  Any metal left bare compromises this. 

If you're concerned about weight, use a thinner Dynamat sheet, or use a viscoelastic 'paint-on' coating.  It runs 60 bucks/gallon, but 2 gallons is usually enough to do the whole car (applied at the thickness of the metal) and adds less than 20 pounds to the weight.  An extra 20 lb on a 3000 lb car won't make a dent in mileage - equivalent to having an extra 3 gallons of gas in the tank.

Check out this page for the 'paint-on' stuff:

http://quietcoat.stores.yahoo.net/

       

A better, more professional "Paint-on Sound Deadener"  is at at
http://soundproofing.org/sales/liquid.htm

BJ Nash - Senior Soundproofing Technical Specialist
Super Soundproofing Co
www.soundproofing.org
888-942-7723


kusojiji

  • Guest
Re: MASS LOADED VERSUS FOAM
« Reply #3 on: June 23, 2007, 11:28:28 PM »
Thanks for the info.  I have a lot of the high density material left and will continue to cover the outer door panels.  Then I'll go with the foam on the inner door panels.

I saw the Quietcoat stuff and enjoyed their cymbal video!


kusojiji

  • Guest
Re: MASS LOADED VERSUS FOAM
« Reply #4 on: July 10, 2007, 01:54:11 AM »
I bought the 1/2 inch thick foam with the adhesive backing.  It proved to be too thick and would not fit in my door panels.

What would you recommend as the minimal thickness for lining a car door?  The 1/2 inch stuff really blocks a lot of noise, but since I cannot cover all of the door, sound is still making it past.  In areas that I could not use the foam, I used the mass loaded stuff.  Again, I could not achieve 100% coverage. 

My plan is to remove the mass loaded stuff and cover the entire door with the foam.