I have a Fractal Design Define R5 case (https://www.fractal-design.com/home/product/cases/define-series/define-r5-black https://www.fractal-design.com/home/prod

I have a Fractal Design Define R5 case (https://www.fractal-design.com/home/product/cases/define-series/define-r5-black https://www.fractal-design.com/home/product/cases/define-ser...) in my living room at the side of my television where I sit a few feet away in a small apartment and can not hear it unless I put my head right next to it, then I can just about hear the case fans. It's fitted with 4 x 4TB WD Reds, a stock AMD Ryzen 2600 cooler, Corsair RM850x PSU and the cheapest graphics card I could find with a HDMI out, the graphic card has a small fan. I also have a HBA card I modded adding a small Noctua fan as they are passively cooled and designed to go in rack mount cases where they have high airflow passing over them so get to hot in a desktop. The case has rubber mountings for the hard drives and sound reducing material on the side panels. I built it to be quiet but didn't go massively out my way or spend massively to make it quieter i.e. I choose a good case but have stock case fans, stock cpu cooler and choose a PSU where the fan only spins up under load which I'll never hit. It's not to hard to build something that for all intent and purposes is silent as long as you don't pimp it out with the latest fastest graphic cards, have it maxed out 24/7, or go small.