Water cooling does not guarantee quietness, you still need fans to pull air through the radiators. The best things for quietness are big fans turning slowly and speed controlled in a case with good acoustic insulation.

The system I built in March is very quiet except for the graphic card's integrated cooler which is very rowdy under load, although I have a custom fan curve set that improves this a little by limiting the fan to 90% of max speed. At idle I can be barely hear my system, I have to look at the power light to see if I left it powered on.

I used a Fractal Design Define Mini C case which doesn't have a window or optical drive slots, so those panels are filled with acoustic insulation. The fans are all X2 GP-12 and GP-14, so there are no case fans smaller than 120mm or exceeding 1200 rpm with no case fans exceeding 19.4 dB(A) at full speed according to the Fractal but they're also speed controlled by the motherboard in response to heat/rpm curves customised by me. The CPU cooler is air, BeQuiet Pure Rock 2 apparently under 27 dB(A) and that is within the case so contains some of the sound (i'd go for a Shadow Rock 3 on more powerful CPUs). The setup was tested by publications that indicated under 32 dB(A) at 20 cm, mine will be a tad louder because I added a 140mm intake fan.

There are quieter cases and fans available if you spend more, but it was under £80 including two good 120mm chassis fans and it's microATX so small and quiet enough to be on my desk, rather than being shoved underneath it. I just need to swap the GPU.

Edited September 20, 20223 yr by ckyliu

Once you have a good case, good fans etc. the weak (=loudest) spot is usually the GPU and it's also the one that is the hardest to change due to warranty issues and potentially breaking the GPU.

In other words, as long as you aren't happy with the sound level of your GPU under load, it basically makes no sense changing the rest.

As far as the GPU being the (loudest) weakest link you can use EVGA precision to limit card to 85-90% power level. This does a great job of keeping the fans from ramping too high at only a minimal hit to FPS.