Not bad
I added this product to the front, back and top panels of my NZXT H710i, the other panel being glass, all to try and reduce the noise a bit.
Well, it's nothing exceptional, frankly I was expecting better, it absorbs a bit of high-pitched sound, I also have coilwhine from my GPU that it hardly reduced.
I used to have a Fractal Design R5 case that was very quiet and whose panels were covered with a sound-absorbing material, but it was different and seemed to work better... I was inspired by the idea there.
I'm aware that the fact that I've left the panel glazed limits its effectiveness.
The plus points though :
- easy to cut with scissors
- the sticker holds very well (be careful when applying it to position it correctly, it'll be hard to remove I think)