I've been obsessed with fans in the past, having build a few HTPCS.
I assume by "mechanical grinding noise" you mean like a rattling noise? yep, that's bearings.
or you mean like the high pitched whine of say, a dentists drill? *Urgh* yep, hate that too.
Coolink swif2 are the only fans I have EVER come across that move lots of air but make no whining/bearing noise @ +1500rpm other than the air whoosh (this is just physics, you can never remove this no matter how good the fan).
Unfortunately they only come in green, no high sp and no damn 14cm's.
Now those fans aren't even half as popular or expensive as Noctua. Yet, to ME, they're better.
Everyone raves about noctua but I rekkon it's *mainly* due to nice boxes and accessories (high quality stuff comes in high qualty boxes right?), which i dont give a **** about tbh. My exp was not great:
-£80 cpu cooler = barely beats stock temps.
-2 of their £20+ fans = meh, ok. nothing special: Still have whine.
-Damn ugly ketchup/mustard cables = More of disgrace than the brown colour scheme (or charging a premium for black!).
TLDR: You really can only go on personal experience: EVEN IF you read all the reviews, benchs, buy noctuas etc, you STILL personally might not like the tonal noise they make.
-As PC777 mentioned, the maglev have no bearings as such, have great reviews, do great in benchs yet I tried 2 sets and sent both back immediately as to me the whine was crazy loud. As exhausts @1800rpm? LMAO... I couldn't believe it - Like a jet engine.
-Phanteks ph-140mp are my newest fans. Tested them against Noctuas and both had a whine starting to be audible at 800rpm. Not bad. No bearing noise even at max, just a bit of whine even @1600rpm.
-Sickleflows used to be quiet I remember, but now there's "better" cheap fans (eg bequeit pure series or noctua redux) that actually push more air - at least according to benchs.
-nzxt 14cms (that come with the x61 aio) are great 800rpm UP TO 1800rpm, only small bearing noise, and at 1900-2000(max) they are absolutely insane, again, jet plane db's from BOTH whine AND bearings!! However... They move more air than most £25+ Noctuas.
Setup is also important to think about, and can often solve most peoples 'annoyances' with simple tweaks.
To me, I TRY to run my fans very low in windows/idle.
Then ramp them up all (inc case fans) significantly for gaming, which you have to do in most HTPC's (even when you've modded the top cover to have 3 x "massive" 14cm intake fans like me!!) because the small space heats up FAST.
Annoyingly for me, my r5 3600 seems to need around 800-1000rpm which is *JUST* where I can start to notice most fans gentle whine (phanteks/noctua/sickleflow) or bearing (nzxt).