Thanks for the reply. What I mean is that if it would increase the reduction rating even more if I will coat it with silicone caulk and then maybe add some extra materials like mass loaded vinyl on top of the foams, or at the bottom?
Edited: Sorry, I just reread your reply and I misunderstood it the first time. Thanks for the help. What do you think is better at blocking low and mid frequency sounds, soundproofing mat or mass vinyl? Also, if it's alright, could you please give me an example of an earmuff with the additional foam that you were talking about and how much noise did it remove?