I cant stand knock tests....all they do is show you how anything that is on the shelf at lowes could do if applied to thin metal
its more about how it sticks and how hard it is to remove so it does not fall off on its own
I tried dynamat pro back in the late 90's and I still have 80% of the roll because It never stuck to anything, most over priced garbage I have ever bought
I just did my front doors with a famous youtube version of sound deadening and the difference is amazing and Im sure your roofs is amazing also