Be anything you want to be

I don't understand Schrödinger's cat.
1) If the box is airtight the cat is dead. Regardless of the poison.
2) If the cat can breathe in the box, then in theory, I should be be able to hear the cat meow. As such if I bang on the box and the cat's alive it will move and make noise. If it's dead, nothing.

And I never have to open the box.