If you have it on the firewall, remove it. Do a search on firewall installation on here, specifically post by Dan Horton.
If it is NOT on the firewall, remove it! Do a search on firewall installation on here.
Seriously though, you should not have any “sound proof insulation” anywhere on the plane. You are using headsets right? If so, what benefit is that insulation doing for you? There is fire/smoke hazards associated with it, but also, it is weight added to the plane unnecessarily with little, perhaps arguably no, benefit.
I think a bigger issue is corrosion.
I’ve seen a couple of absolute shockers. Almost write offs…
A lot of these trap moisture, right next to the skin.
I’d never glue anything to the skin, that’s just asking for trouble. Especially on floors.
Does the adhesive on Velcro count?
Where the surfaces that corroded painted or bare aluminum?
While I do agree about such material on the firewall, this seems a little over the top. The same fire hazard argument could be made for any installed carpet and seating materials in the plane, or for that matter, any polyester garments. I for one want a few creature comforts in my plane. And headphones or not, any sound deadening effect lessens noise and is therefore of benefit. Whether it’s cost effective and worth the weight penalty is up to the owner.