I don't understand complaints about the noise of the Scythe fan. At 1800 RPM, it's rated at 100 CFM and 26.45 dBA.
At above 900rpm it starts to buzz/hum kind of like a distant airplane. Some say it is whisper quiet at under 900rpm, but I really don't think so. Around the 650rpm - 700rpm range is where it already becomes clearly audible regardless of whether you sit at a farther distance than several ft. away. (And then I am not talking about audiophiles who can still clearly hear it even if it runs at a much lower rpm than this.)
Noctua doesn't have an exact match. Their NF-A14 industrial ppc 2000 PWM does 107.4CFM (182.5 m3/hr) at 31.5 dBA. Another 140mm fan with 1500 RPM max fan moves 82.5 CFM at 24.6 dBA.
Their Industrial PPC line of cooling fans are NOT designed for what this subject is about. The primary goal in this instance is to be able to achieve the same or better cooling performance at a lower noise level and/or less irritating (subjective, but not 100% subjective IMO) characteristic of the noise when compared to using 120mm fans and/or when compared to using fewer fans. That is, by lowering the rpm of the fans, BUT... while still keeping the
option of being able to increase the cooling performance momentarily if/when needed of course. It is this
option where the noise difference between the Scythe Kaze Flex 140mm PWM and the Noctua NF-A14 PWM becomes more prominent further still. But even if this doesn't actually matter to you all that much, Noctua offers double the warranty period of the Scythe, and, I generally dislike the idea of a fan starting to rattle/click/stutter on me at a highly inconvenient time so, the ability to noticeably reduce this risk at the sacrifice of spending some additional money also translates to better peace of mind. You'll just earn most of it back from not having to replace fans as frequently anyway in the first place. Really.
No fan I've ever chosen was quiet at maximum RPM. The fan controller is set so the fans aren't run at max unless necessary (which is rare).
I suggest studying and comparing specs when possible. Don't take any free advice here as absolute. Including mine.
You cannot understand life and its mysteries as long as you try to grasp it. Indeed, you cannot grasp it, just as you cannot walk off with a river in a bucket. If you try to capture running water in a bucket, it is clear that you do not understand it and that you will always be disappointed, for in the bucket the water does not run. To “have” running water you must let go of it and let it run. The same is true of life and of building a PC.
