I recently bought two PH-F140SP_BK from newegg with the 20% off code and adore them. My comp sits right behind my monitors on my desk so having quiet fans is important to me. Aside from the faintest sound of air moving, they're silent. No fan buzzing, whirling, whining, or humming can be heard.

It's not the exact same fan as the HP, but they're both rated for 19dB so I imagine they're very similar.

 

HP is TS with PWM

See the silentpcreview review btw

http://www.silentpcreview.com/article1345-page4.html

Hardware.fr puts them pretty good in terms of cfm/dB
http://www.hardware.fr/articles/886-26/recapitulatif-db-a-vs-cfm.html

same for Hitechlegion http://www.hitechlegion.com/reviews/cooling/heatsinks/37600-phanteks-f140hp?showall=&start=2

Arctic F14 isn't really worth it, those are rifle bearings and Phanteks has better performance and a 5 year no hassle warranty akin to Noctua's 6 year warranty

The Cougar HDB fan is supposed to be good but there's reports of slight mechanical noise and PWM ticking at low RPM. It also comes down to the sample variance.