Not nearly as quiet as a big can like the FTN, but I don't have any way to quantify. It does take some of the "edge" off but it's not hearing safe. If I had to guess, it brings the 9mm down to about the level of an unsuppressed 22LR, so probably a 10 - 15 dB reduction.
The advantage the Khrizantzema has is that it's a flow-through design so you get a lot less backpressure than a traditional baffle can like the FTN series. On simple blowback PCCs, that beats up the gun less (you don't get a big increase in bolt opening velocity) and puts less additional gas out the ejection port. On a bullpup like the Urutau where your nose is literally right above the ejection port, that's a big win.
Any of the "engineering-grade" materials (PA6-CF, PA612-CF, PA12-CF, PPA-CF, PPS-CF, etc.) can work well for suppressors assuming:
Technically, achieving good layer adhesion is the biggest challenge. You need a somewhat controlled environment so you don't overcool the layers and you need a printer that can maintain extrusion temperatures of 300 °C or more with margin. Process-wise, people often try to take shortcuts on drying and annealing resulting in poor strength and lack of heat tolerance.
What you'll get with the advanced materials is reduced baffle erosion thanks to the greatly improved heat tolerance. But it's still fairly easy to melt one down with high-volume, high-rate fire.