Dynomat vs. Fatmat?????

[Wolfgrey04]

Anyone familiar with Fatmat? I've used dynomat before but the cost is too much for what I wanna do. I'm looking at covering basically every square inch of interior sheet metal with sound deadening. However I really don't want to spend a thousand bucks doing it. Any details or personal experiences would be appreciated

[Da67goatman]

Use lizard skin, its spray on and weight is like 15 lbs for a bucket.  Much better than any mat product, plus you can do inside and underside as it acts like an undercoating as well.

[bake74]

Use lizard skin, its spray on and weight is like 15 lbs for a bucket.  Much better than any mat product, plus you can do inside and underside as it acts like an undercoating as well.

     Vile has used this product.  It is also easy to spray in the doors (after taking the windows parts out) for added sound deadening properties.  Then if you are not satisfied you could always put the mat over the top of it.

[slammed79]

I'm planning on spraying my can with this stuff too. I've read really good reviews on it

[ehjorten]

Covering every square inch of the interior is a complete waste of money!  You don't cover every square inch; you cover the areas where sound is transfered into the cab.  That is not every square inch.  Spray-on stuff won't do much for anything but high-frequency buzzing.  You should start with the firewall and the floor.  That is where you get the biggest bang for your buck.  Then the backwall and sides.  Last is the roof.  You want to cover large flat areas of sheetmetal.  But for this you need to use a foam mat with a heavy rubberized de-coupler on the top.  This is the best for absorbing and reflecting back that air-borne noise that turns the large flat areas of your cab into a speaker.  For thermal insulation you can use a foil backed adhesive insulation.

You really don't have to cover everything.  magazines and shows that show guys covering everything are wasting your money!

Finally...don't use anything in your interior that is asphalt-based!  It will stink-up your interior and also in the heat the adhesive will migrate out of the material and come loose from your sheetmetal rendering it useless.

[Captkaos]

Bquiet sells some relatively inexpensive sound deadening, but I wouldn't put it everywhere.

[ehjorten]

Here are some resources for those hardy enough to read them.  I have some other SAE White Papers regarding Noise and Vibration Damping, but I can't post them here and you need a subscription to view them on the SAE website.

Designing For Quiet Vibration-free Operation

The Four-fold Method of Noise and Vibration Control

Heavy-Duty Noise Control

Understanding Damping Techniques for Noise and Vibration Control

My colleague at work has recently applied these techniques to his 60's Rover.  He started out at about 107 db in the cab (which is close to the level of a chainsaw at full throttle!...This vehicle is just riveted together aluminum cab with very little in the way of insulation or anything, and it has straight-cut gears so it is loud!!).  He applied insulation and noise damping to the firewall just up to the bottom of the dash and covered the floor.  He is now running about 84 db (which is just loud enough that you have to raise your voice slightly to talk.).  He has plans to do more, but it is camping season and he is driving the Rover a lot.  Now they don't have to wear hearing protection when driving the truck!

A halving of the sound power is equal to 3 db.  Halve it again and it is another 3 db.  Sound pressure is on a logarithmic scale.  Going from 107 db to 84 db is roughly about 1/128th of the sound power!