
Help fixing a bad soundproofing window with roller shutter
I have these soundproof windows that don't work very well. While the glass panel part actually works okay, I found that a lot of noise passes through the compartment where the roller shutter is kept. Here's a picture: https://imgur.com/a/R6K4UPl
After opening the compartment I found that there's basically no soundproofing there at all. It's hollow compartment made of metal, with a very thin layer of something lining the inside. (Image of the inside also available: https://imgur.com/a/R6K4UPl )
So basically that makes the glass soundproofing kind of useless since the sound just goes through the metal compartment at the top.
My question is: are there ways I can manually fix it? My intuition is to just get some insulating material and line up the inner chamber. But I'm not sure what to put there. I could also put something on the outside. It wouldn't be pretty, but as long as it works I wouldn't mind.