consistency in quiet 80 mm fans

[Aracu]

In making a careful but low tech comparison between a few quiet
80 mm fans (Nexus "17.6 dBA", SilenX "11 dBA", Pabst "12 dBA", and
Yate Loon 8025M), they seemed to be surprisingly consistent with one another (except for the useless clicking Pabst) in that the louder the fan was, the more air it was blowing and the higher pitched it's motor hum was.

From loudest to quietest, in my opinion: 1. Yate Loon at 12 volts 2. Nexus at 12 volts 3. SilenX at 12 volts 4. Yate Loon at 5 volts 5. Nexus at 5 volts. The SilenX woudn't run at 5 volts.

Nos. 3. and 4. were approx. the same volume level, with the SilenX pushing more air, and producing a noise with a more pleasant sound quality, even though higher in pitch.

The Nexus at 5 volts is stunningly quieter than the rest, but I don't know if the principle of using numerous quieter fans rather than fewer louder ones applies if each individual fan is hardly pushing any air at all.

It's hard to imagine how the CFM of a fan can be accurately measured.
The SilenX is rated as having slightly more CFM than the Nexus at 12
volts, but it obviously pushes less air.