If you're consistent you should reach the point to where you don't need an alarm and your body is capable of waking up at the same time everyday.

However even if you're wearing earplugs you'll be able to hear an alarm, they don't block off noise that much.

Earplugs don't actually block out a whole lot of noise.

For example, if I wear my earplugs in the library, it'll completely muffle the sound of people whispering around me, but I'll still be able to hear the oblivious jock talking at full volume to his buddy at the table across from me.

Earplugs don't block out all noise. You will still be able to hear a loud unwanted noise near to your bed.