It's the windowless version of the Fractal Design Define R5. The panels are all lined with padding to reduce noise. I have a single Noctua NF-F12 moving air through it. It's capable of spinning to 2,000 RPM if needed, but it never gets hot enough inside to ever spin faster than 1,200. Even at full speed, the fan is still very tolerably quiet. I only bought the ippc version because it wasn't brown and brown.

Also, the CPU is a 4790K cooled by a Noctua NH-U9B SE2. It's a 92mm cooler that fit nicely in my old "Optimus Prime we have at home" case. It has two fans on it that run at a constant 900 RPM. It does a great job keeping heat in check at stock clock, but I wouldn't trust it in an overclock situation on this CPU.

Not OP but I went on my own crusade against noise a few years ago. I had a ryzen 1600 and a 1070 in an NZXT S340 case using the included case fans. I wanted to get rid of noisy components entirely instead of using any kind of sound isolation or insulation because I thought it would be easier to get rid of the problem at the source than to try to hide it. I replaced both case fans with be quiet shadow wings 2s and got a be quiet dark rock 4 to replace the stock CPU cooler. My CPU never used more than 100w but the new cooler was rated for 200w. I thought it would be quieter to have an oversized cooler for my CPU since a bigger cooler would need a slower fan speed to get rid of the same amount of heat as an appropriately sized cooler. I also got a 850w power supply with a mode that turns off the fan completely if it's using less than 200w. My whole tower used around 300w when playing the games I normally played and around 100w or less while doing light work. I tweaked the fan curves of everything so temps stayed under 50C with light loads and all my fans stayed at about 900rpm. Every fan got faster and louder while gaming but I didn't notice or care since it was quieter than the sounds and music of the games. After I got all my new fancy fans my 8TB internal HDD became by far the noisiest thing in my whole set up so I built a NAS with hand-me-down hardware and put all my spinning rust storage in a different room. Since then my only upgrades have been a bigger SSD and a ryzen 5800X CPU.

In the dead of night when the whole house is quiet my own breathing is louder than my PC 2 feet away on the desk if I'm not gaming.