Reese asked me today at lunch "Why can't I talk out my eyeballs?" I swallowed my instinct to giggle at the sheer cuteness of that question...and we launched into a discussion about anatomy!
I explained that his throat has vocal cords & like guitar strings being strung, they vibrated when you talk. We put our fingers on our throats and made the "aaaahhhhh" sound and he lit up as he felt his vocal cords vibrate in his throat. Then we made the "sssss" sound and found out that not all the sounds we make come from our vocal cords.
Then I explained that his eye balls don't have vocal cords & therefore can't make sounds.
You should have seen the understanding & satisfaction on his face...a true grasp of why we talk with our mouths!