Hi JustDIY and Sceadwian,
The mechanics (bearing surfaces) of the fan are fine and the blades are clean. It's a fluid dynamics issue. The speed is excessive, hence the wind-noise. Thermally, at current RPMs, things are overcatered for.. the fans don't need to rev so high. A 40 to 50% reduction in RPM would still be adequate for cooling.
I want to be able to proportionally vary the voltage - reliably and efficiently. I'm generally good with a soldering iron and would like to 'perfect' this project.
Re: "any sort of external speed controlling device you cook up will prevent your system from monitoring the cpu fan, which in general is a bad idea" I take your point. Hmmm - so where to from now?
It is definitely (zero-point-zero-eight ampere) 0.08A. Rather efficient for a 'standard' 80mm fan, but it's not really the noisy one. The noisy one is the CPU fan which is 12V 0.28A - with 3.5 times the power consumption.
I did check out the BIOS (beforehand) and I have no means to regulate the speed via this method. I can only Enable/ Disable but little else. The BIOS option is annoyingly very limited despite it being a 4yo Gigabyte GA-8IPE1000 Pro2 mobo. And yes 'fan feed back control' should mean "control" but it doesn't (much) in this case. "Full bore" is all it seems to understand. I'll report back re those sites you recommended JustDIY.
I live in hope that my next PC mobo will have several BIOS fan speed control options.
Re PC case air temperature concerns: I designed a PC air filter for the fan driven incoming air. Internally, I now rarely have to clean my fan blades, heat sinks, PSU, etc. I come from an audio background and I want (am aiming for) an absolutely quiet PC. If my radio or hifi had hum, it'd be a fault, and so I'd have it fixed or relegated to a noisy environment. Seems PC engineers and their companies are mostly too busy 'gaming' aka, playing with themselves to worry about a more discerning market. 'Just quietly', this could be 'game on'. Thanks guys. Regards, Cooee2.