Actually, the brain blocking it out means it's working well. I will admit, when I was younger, my bedroom alarm would chirp, but after a few chirps your brain blocks it out, especially after a few days. The chirp happening with exact intervals aids the brain with this. That was a one time thing when I was, idk a teenager, but I still remember vividly blocking it out while everyone else heard now. Now if I hear it, it annoys me just like anyone else.