I know a ton about this stuff. I used to formulate commercial roofing products for a competitor of GAF the manufacturer of "ruberoid". I learned quite a bit about their commercial product lines. These types of products are basically comprised of a thin sheet of reinforcement made of either fiberglass or polyester. This sheet is ran through a molten-hot mixture of asphalt and modifiers. The modifiers generally consist of Styrene Butadiene Styrene (SBS) rubber or plastic (either atactic polypropylene or isotactic polypropylene). There is usually a certain amount of calcium or magnesium carbonate in the formulation that serves as a filler. The coated sheet is then ran through a water bath to cool. The thickness of the material is typically 4mm.
I suspect that the CaCO3 aids in sound absorption because it tends to make the product weigh more/unit of volume. This would reduce vibration. I read an article about this before starting construction on my studio. I read where it was recommended that it be placed wherever a top or bottom plate touches the external structure. Since I had excellent access to this material, I decided to implement this idea.
I had to decide on whether or not to use APP or SBS because the SBS polymer is more flexible and there is typically more CaCO3 in the formulation. However, it is difficult to find an SBS sheet that is 4mm thick of just modified asphalt. Typically, the modified thickness is something like 3mm, and the rest of the thickness is made up in the form of granules. I ultimately decided on the plastic modified version (APP) over SBS because I could get 4mm of pure modified asphalt without granules.
