I finally had to do something about the noise, My sound barrier Options

[DNHunt]

I found a product called Quiet Zone made by a company called Ixos. It has a 3 mil aluminum layer with a 1.5mm visco-elastic layer. They put it directly on painted metal but, I still have visions of rust repair so I came up with a different idea.

I put a 2 mm form layer on the 2nd layer. The gray stuff is the visco-elastic layer and the green is the foam.

[Katmanken]

Fer sound deadening you want the visco-elastic layer firmly attached to the firewall...

Ideally, what you want is the vibration transmission surface (firewall), the visco-elastic layer firmly attached to the firewall, a secondary mass attached to the other side of the visco-elastic layer and something attached to the secondar mass to absorb sound.

Models are: big mass-spring-secondary(smaller mass)-noise absorber (foam, green stuff, etc)

O-w-o-H where O is the firewall mass, w is a spring (foam, visco-elastic layer), o is the secondary mass (weights, lead sheet, lead in vinyl) and H is the sound absorbers. Foam is good for lower frequencies and the silver mylar is good fot the high frequencies.....

I spent years quieting down dot matrix printers with foams, masses and a sound meter. For the print surface it was a steel bar, vinyl glued to the bar, and a steel strip for a weight.

Best stuff was glue, foam layer, vinyl with lead layer, more foam and then silver mylar on top. All glued together. Velcro might not provide enough solid coupling for the visco-elastic layer to do it's thing... Give it a try and see...

Ken