Power circuitry of hungry graphics cards (higher currents than in low end cards) can squeel and whine etc and you have there two ultra hungry heating Fermistors so that would be strong candidate.
Coils in CPU's VRM circuitry can also keep noises but that varies basing to CPU load so any CPU stress tool would affect to noise. (have you tested that)
it could be a capacitor whine
Why don't you stop repeating that automatically like some parrot and think for yourself?
Capacitor is solid component without nothing loose in there, that includes electrolyte capacitors whose electrodes are equally tightly rolled with just electrolyte soaked paper (in place of insulator of plastic film capacitors) between them.
It's coils whose wire loops can vibrate easily when pulsating current/magnetic field happens to cause resonances in them.
That's why putting some temperature withstanding glue or lacquer to coils is commonly used method for trying to stop these noises.
mine does it on certain games on loading screens, it dosnt bother me that much.
That's one of the basic places for graphics card to squeel/whine etc. because without real load frame rate shoots up changing GPU's current drawing frequency which might hit to near resonant frequency of some coil in power circuitry.
Motherboard integrated software sound cards again can pick up interference from pretty much anything on motherboard and from any current/signal going through it.
