I'm very sensitive to any sensory stimuli, not only noises. I do usually cover my ears when I hear something like sirens or whatever much louder than usual, because it almost hurts physically. Also maybe it depeds on the frequency as well. Or if I don't cover my ears I cannot focus on anything else anymore.
That means also that on the other end, I notice things, sounds, etc that people don't notice. This can viewed as good or bad, depending...But I think it's mostly genetic, some people are more sensitive, it doesn't have to be pathological by itself I think...
Also I think it can come from some childhood trauma, but in that case it would be very specific, I don't know, just my opinion...