First of all,my apologies for not replying soon enough.
So,let me describe even further what happens to me and then i'll tell you my thoughts.
First of all personally i believe that sometimes my hearing is pretty sensitive.
Most of the time i get a high pitched noise like you are.
Other times,mostly when i'm facing to the right,i can hear the air getting through a small opening from my balcony door (needs to get fixed
the sound of the cars from outside allthough sometimes they sound kinda weird.
(both situations happen when i'm in bed)
The second part was just to show that sometimes when you hear something it can be the most simple thing in the world.
So,about the high pitched noise.I've thought a few things about it,even that "someone" wanted to "communicate" with me.I've also thought that it
might be from antenas that are low enough and somehow they're affecting me (yes,i know it sounds silly but it was just a thought).But what i believe
is that it's just that i'm used to noise.
Every single day,one way or another noises are all around,so,personally i believe that it's just something like an echo that remains in our ears when
everything else is quiet.
Anyway,i wont be around in this thread because it allready started taking the "paranormal" path of explanations and i'm in no mood to be the
"skeptic" guy of the thread.
If you want my advice though,consider the rational explanations and possibilities first and if you wont get any answers,then you can proceed step by
step to more complicated views about it.