Sound and heat Insulation

There's a lot more to the soundproofing game than I knew when I started this job. Since this is the first vehicle I've insulated completely, I decided to conduct some research instead of simply ordering materials based on the best advertising. I have no reason to become an expert, nor do I need a car that's as quiet as a Rolls Royce, but I don't want a rattletrap either. When I restored my '73 Dodge truck, I discovered that it contained almost no insulation from the factory, so I just covered everything with FatMat. It made a world of difference in quietness, and I hope this car will be even quieter.

What I did learn this time is that despite all the manufacturer's advertising hype, modern cars basically use two types of products to control heat and noise. The one for heat and airborne noise absorption is HDF, or high density foam. It absorbs, deflects and shields against external noises, like engine, exhaust, and road noises that sneak through cracks and gaps. For this part of the project I ordered a 1/8" self-adhesive roll to apply to the firewall and the inner door panels.

The next is CLD, or constrained layer dampers. This product dampens acoustic vibrations in places like floors, roof, and trunk areas. For this, I bought a product called Road Kill that is self-adhesive and foil covered on one side. The thickness of both the foil and the damping material affect the efficiency, but for the areas I'm doing now I chose a thinner material that will fit between trim panels and structural metal. Yesterday I applied it to the inside of the roof and a few places on the inside structure. The supplier recommends that approximately 25% of the surface be covered, but I found that to dampen all the vibration in a large panel like the roof, I had to cover approximately 50-60% of the surface. Now when I tap the roof, instead of reverberating like a Caribbean steel drum, all I hear is a dull, metallic thump. Since the headliner will also help absorb noise from above, I might have overdone the Road Kill, but a few dollars extra at this point beats having noise that would require removing the headliner to fix.

They also make composites that both absorb vibrations and acts as a barrier to airborne noise. I plan to use this on the floors, but so far the prices I've found were too high for my budget. I might just use a heavier version of the Road Kill product I got from Amazon.