When my muse grips me, i'm gone. I can block out extreme heat, hunger, television, crowds, and personal tragedies while seriously writing. It's a bit weird too because i can't read a book in a crowd of people, but i can easily filter out the billions of sounds made by throngs of people when i'm writing. Maybe it's easier to immerse oneself in their own world rather than someone else's. My parents hate it, they'll call my name close to a hundred times and when i do finally answer and do what they ask, i'm distracted and spacy.
I've got two modes while writing. One, where my muse is kind and the paragraphs flow out like water and i'm merely distracted from the sheer pleasure of it and two, where the writing is like cutting my arm open and bleeding myself for every little word. Obviously mode two is where i'm consciously concentrating. Mode one is more just me basically enjoying a literary orgasm.