A jet engine?

Really though, my Antec Tri-Cool fans run and 30db max speed and you can hear it with the tv off or no sound . At low 25 db I can barely here anything. The CPU noise will be muffled a bit by the case. You'll probly here it pretty good, then again if your not gaming you can lower the speed manually or just leave it automatic and it will lower. You'll be hearing game sounds anyhow so it shouldn't matter much.

Hell I leave all 4 (x30db) of my 120 MM fans running @ 100% + the CPU Fan (stock) @ 100%. The "white noise" doesn't really bother me or make enough sound to interfere with my Television or Music. My case has acoustic dampening (Antec-P182) so the 50db fan wouldn't be quite so much. I probably wouldn't notice it much at all.