ok. good points.
I dont think my fan is worn in any way. The noise is a ringing, not a mechanical issue. The controller I showed , as I mentioned, is similar, and I am not able to find anywhere the exact controller online anywhere to be able to look at its specifications... It might operate in the human ear range and be audible.
The FF has coils that act like a heating element to burn off power. However you want to exactly define what a heating element is or not does not matter bc in the end it still is doing the same thing, heating up a wire at the expense of power. I thought I used words to give clues that this is not important nor something that matters or needs further discussion. What I keep try to say politely is that I dont really care if you call it this or that. Nothing changed now that you defined it. It is hard to write on a forum post something that can both be understood and polite, I tried. Now lets stop with the heater analysis....