Once in a while I hear some sort of screeching sound, sort of like that unpleasant sound heard when you scratch a sharp object against a chalkboard. Whenever I hear the sound, its sort of in a low tone, so it's as if the sound is either on my head or it's coming from somewhere very far away. Whenever I ask those beside me, they say that their not heating anything. So my question is:
Is the sound coming from my head or I'm just the only one that could hear it?
Is such scenario normal or abnormal?
Is the sound simply produced by the wind passing by my ear?