In a room full of power supplies i was the only one able to find which one was still powering something, because apparently out of the ~20 people that tried before me, i was the only one that could hear the transformer whine.
Also a general annoyance since i need to charge my phone in another room if i want to sleep without simulating tinnitus.
SO that's what I keep hearing in those dame phone chargers.
I don't hear it all the time though, it sometimes starts happening and after that never stops. I believe it is that something breaks or is about to break that makes me suddenly able to hear it.
If someone more knowledge, knows what's up with them please tell.