and even when you bleed all the air bubbles you can, you still have some left, and they do make noise.
No i dont have a link to how much noise bubbles make. But they are audible, and my air cooled rigs are not. So its louder than air alone.
I strongly disagree here.
You CAN bleed the bubbles out properly with an airtrap, the most popular one currently is the Swiftech Micro Res, a very well thought product that does exactly what it's advertised for. We're starting to see other kind of airtraps around... before that it was a DIY job (as i did). Once all the bubbles are out, a decoupled pump makes zero noise.
I recently built 2 systems with that mini reservoir, both are now very quiet (each had 2 fans + the PSU). Zero bubble in sight.
Again i repeat in such watercooled systems the only noise comes from the very few fans that are left, and the muffled HDD's.
Some people (typically in Germany) go as far as using huge radiators to cool them passively, thus achieving a zero fan setup.
And again, it's easier to cool a lot of hot components with a water system, and a properly mounted radiator, than trying to cool down multiple small hot spots at different places with slow moving fans (which wont allow high performance / overclocks, especially on hot days).
It's also easier to move away the cooling component, if it has to be noisy (radiator + noisy fans), to another room.