As ever I like to begin my summary by explaining that your first consideration should be that the db rating doesn't tell the whole story. Tone, resonance and other factors can and in many cases are more important than pure sound levels.
Motor wine, speed related clicking and bearing noise may not show up on the sound meter but when present I can confirm that they are very apparent and can be annoyingly intrusive. On the flip side you could have a fan that made no discernable whining or clicking but registered a high decibel count! In that scenario I'm sure most users would prefer that kind of sound profile over a low decibel rated fan that clicked and whined.
The NZXT fans in each case delivered a smooth sound presentation despite the higher than normal decibel ratings. Resonance, chuffing and motor whine are nonexistent with only minor chuffing apparent at high RPM's.
Both fans are rated to run at a relatively conservative minimum speed of 1000RPM when the onboard switch is set to 'Low'. At this setting both fans successfully spun up from a stopped position. This speed is actually fairly close to the 12v speed of the average quiet fan. At this speed back pressure is surprisingly powerful and certainly the equal of any standard quiet fan I've used. The 120mm NZXT is understandably a touch quieter than the 140mm when running at this RPM since it's physically smaller and pushes less air. Both fans produce a fairly similar smooth sound profile although the 120mm shows the very slightest hint of clicking at this low speed which is only apparent when I placed my ear right next to the fan during testing.
Upping the onboard switch to 'Medium' we get a pretty noticeable surge in performance. Indeed, even at this setting these fans are rotating faster than any of the other fans I've tested at Vortez. The sound profile of the fans retains the same smooth presentation with just an increase in wind noise. The db ratings are high but that smoothness of presentation gives the impression they're running quieter than the SPL meter would suggest. Once again backpressure is very impressive indeed - the increase here is considerable and airflow can still easily be felt a distance away.
Full speed mode was selected in each fan by flicking the switch to 'High'. It is here that the high performance nature of this enthusiast fan really lets itself be known. At this setting the 120mm fan runs at 2600RPM and the 140mm at 2000RPM. This is now completely out of the ball park compared to any other fan review conducted here at Vortez. By now the physical movement of air is reaching pretty epic proportions and to a certain extent the noise output is following suit. You certainly wouldn't miss a case full of these but again that noise signature is smooth and both click and whine free. Backpressure is absolutely excellent here too - certainly much better than any other 120mm or 140mm fan I've tested. These are truly performance fans!
