Is it normal that i hear this?

It's just an auditory hallucination from having a fan blowing right near your ear. The human brain is wired to find patterns in chaos and recognizable order where there is none- the most simple example is seeing shapes in clouds. I used to have a fan right next to my bed, and I could swear, I would hear the sound of people murmuring or even music sometimes- really quiet. It's just from the air moving across your ear. It'll go away if you ditch the fan.

During my life I have encountered many different random, bizarre occurrences. Nothing exactly like you're describing, but I said that it's nothing to worry about. Just tuck it away in your mental rolodex and maybe at some point synchronicity will show you the nature of this. It could be many different things. Some bleedthrough from a different dimension, could be somebody that astral projected maybe. Did it sort of come from inside your head? did you have any malevolent/benevolent sense? I had such a thing that it was a sort of a voice the only time I ever heard it (not hearing voices as a mental condition). I knew it was real bcuz it made sense years afterwards it was significant and I was unaware at the time. It could have been a form of telepathy? IT's really hard to say. I would just say, to rely on your intuition.

It sounds like Paranormal Activity. Have you tried talking back? Maybe if you try getting to know these entities, they won't seem so scary. I recommend a Medium (a person who speaks to spirits).