DIY Trumpet Soundproof Box

This is a homemade soundproof box for a trumpet.
It features a wooden frame box with Daiken soundproofing sheet 455H, polyester sound-absorbing material PolyLeaf, and gypsum board on the bell side.
A hole is provided for the bell to be inserted directly during normal use, and it can be sealed for maximum soundproofing.
It opens like double doors, so if the depth is sufficient, a flugelhorn bell will also fit.
The gypsum board at the corner is damaged.
Please understand that this is a homemade item, not a manufactured product.