Try Noiseblocker:
http://www.noiseblocker.de/en/BlackSilentPro120.php
http://www.noiseblocker.de/en/Multiframe120.php

Very quiet for their rotation speeds - I use the 140mm Blacknoise Silent Pro PK3 fans and at 1700RPM the motor noise is totally thwarted by the whooshing of air rushing through the fan.

The 6 year warranty and declared MTBF of up to 180000 hours do confirm that the manufacturer did an awesome job with the fan bearing.

Some AirPenetrator fans by Silverstone are capable of delivering very decent airflow (I love the gargantuan 180mm fans that came with my Raven case) but they are noticeably louder than their Noiseblocker equivalents.