It's the first time I read of someone having my same troubles
I have very sensitive ears and tend to hear electrical high pitched noise almost everywhere.
I can also hear it from notebook chargers (bricks), AC to USB chargers, a USB hub (!).
I owned a lot of low to mid end PSUs, maybe we can figure out something.
Among all the PSUs I have owned, all of them except one produce high pitched noise:
Antec Neo Eco 400M - my newest unit. The electrical noise can be heard even from almost 2 meters away, it's quite disturbing and present only when pc is on and at low loads (approx. 40-50W). In addition to that the fan is just ridiculously bad.
5 Corsair VS450 - these are actually one of my favourite PSUs: decent quality and sold at ridiculously low prices. The noise can be heard only from extremely close, and only directing my ear exactly towards the rear of the psu. Therefore once it's installed in the system it's impossible to hear.
3 Cooler Master B500 - same as the VS450, but slightly louder noise.
Cooler Master GX 550 - The only psu that doesn't have this problem at all. It's a very old model, probably more than 5 years old. It isn't certainly a high end psu, but I've always admired its ability to work correctly in very uncomfortable conditions, for example with the exhaust air from a Hyper 212P on a Phenom II X4 955 @4,3Ghz blowing directly into it, resulting in burning
hot air exhausting from it. It's been working in such conditions for 4 years, and it's still rock solid.