What kind of fan filter is this?
What kind of filter is this

It's a "Oh crap, this thing failed FCC testing again.  My boss is already pissed, and if it doesn't pass next time, I'll be fired.  If only I had actually paid attention in school instead of getting homework answers from EE.SE and copying test answers from the guy next to me.  I remember something about inductorators and capacitators getting rid of high frequencies.  [23 seconds on Google]   Ah, here's something.  It must be right.  Someone named Anne Onimus says so.  She must be an expert or something.  I'm not sure what those 4.7 &micro;H and 470 &micro;F mean exactly (and why can't they write "u" right?), so I'd better copy it exactly.  Hmm, wasn't there something about types of capacitators for different frequencies?  Something about ceramics for stuff that radiates?  Nah, ceramics are for pottery.  I'll just do what Anne says here.  Oh oh, what if this isn't enough?  I know, I'll use two of them!  Wait, I can't afford to fail again.  I'll use 3.  No, wait, if 3 are good, 4 must be better!" filter.