Fans tested, all 120mm, all at 1028RPM:
Scythe S-Flex E
Scythe - Andy Sam
The Scythe Andy-Sam has a single-scythe logo on the front of the hub. The Scythe S-Flex and the A-C PWM both have 1.85" hubs; the other hubs are 1.5" except the NCB at 1.6". The NCB you should all know.
Here's the scary part: the first 4 fans on that list all sounded exactly alike, both in intensity and chraracter. All five fans seemed to blow the same amount of air on my face, as far as I could tell. The NCB was about 2.5 times quieter when you ignored the whoosh and listened to what was left over.
If it wasn't for the NCB, the sameness of the remaining fans would convince me I wasn't hearing bearing noise at all, just fan blade noise. Except the blades on the NCB aren't different from the other fans, and the noise I was hearing from it was dramatically different in comparison to the sameness of the noise of the other fans. We're talking identical quadruplets here.
It has to mean that Scythe and A-C buy their fan bearings from the same source. Not only that, but the same model bearing. Which doesn't match the claims of eternal life for some of the fan models but only 30,000 hours for the new Scythe PWM.
I did hear a very slight higher frequency edge to the Scythe PWM bearing noise. Very
slight, but it was there at times. I tried the other Scythe PWM, and couldn't duplicate the effect (I have 2).
I set my strobe to 1028RPM, and used the voltage controls on the Rheostat to synchronize the fan speeds to the stroboscope. Very easy, very fast. This time I used only a slight dab of white thermal grease on the hub of the fans with no front label.