I have four fans on hand, and I've made a brief objective and subjective comparison. The four are, in order from loudest to quietest measurements
Yate Loon D12SL-12 (low speed) - rated at 1350RPM. 0.3amp
GlobalWin NC Bearing 1202512L - rated at 1300RPM, no current given
SilverStone FN121 (aka GlacialTech, aka Everflow R121225SL) - rated at 1200RPM, 0.2amp
Scythe YLTC, model DFS122512LS - rated at 1200RPM, 0.18amp
I measured them at a very close range with my Radio Shack sound level meter (analog meter) -- close range because the meter can only measure down to 50dBA. I used A weighting, and "fast" response. With the meter, I measured them on the "intake" side so as to avoid the noise made by the moving air, and the meter's microphone was closest to the tips of the blades. I measured them at 12 volts, 7volts and then 5 volts.
Subjectively, I listened to them all at 5 volts only, holding them very close to my (good!) ear; both on the intake and the exhaust side. Subjectively, the order shifted, slightly:
The Yate Loon measured the loudest at all voltages, and it was the loudest subjectively, as well. It was close at 12volts, but a lot louder at 7v and 5v -- the step down to the GlobalWin was a big one at 7v, and even bigger at 5v. Subjectively it is very smooth, with no apparent bearing noise; just a pleasant hummmmmwhoosh.
The GlobalWin measured second loudest across all voltages, and the step down the second quietest fan was fairly small. Subjectively, it has a slight
bearing rub, and a low hum.
The SilverStone measured 2nd quietest at 12v, quietest at 7v (by a smidge), and 2nd quietest again at 5v. Subjectively, it has a very small
bit of bearing rub, and a lower pitched hum than the GlobalWin.
The Scythe was a surprise, since I have read several folks who feel this one is loud. It measured the quietest at 12v and 5v, and 2nd quietest at 7v -- again the range of the three quietest fans was small. (Maybe I'll have to figure a way to measure the hub noise?) Subjectively there is a more rapid, but ever so slight bearing noise (only audible about an inch from the support side of the hub), and the overall noise level is very low indeed. The only caveat is the Scythe did not start at 5v when horizontal
and barely started when vertical.
Links to where I bought these:
[Edit: I meant to have this in the review (so, now it is!): The Scythe fan is made by Young Lin Tech Co., LTD., and it's model number DFS122512L(S) seems to be the Young Lin part number.
And actually, all four fans have closed corners!]