I see I'm not the only one with a chatter monkey! I totally understand the mental exhaustion. My son is Gerald McBoing Boing most days and it drives me insane.

What I do is frankly tell him he's bothering me. It sounds mean, but he doesn't really understand that it IS annoying and distracting. I'm an introvert myself and need my quiet time too. He's learned that if I have a book cracked, he should not be disturbing me.

I tell him just because he thinks it in his brain doesn't mean it has to come out of his mouth wink

I can't find a reference, but I either recently read or heard on TV that kids who chatter and make noises can have an OCD thing going on. Meaning the humming, chatterboxing, and other noises are a way they self-soothe. If I can ferret out a link, I'll post.