Here's Baby running around his cage being silly in the middle of the day. That "Ah-Uh" sound he makes repeatedly is his general "I'm having fun eating/playing/being silly" sound. It was also his "thank you" when you would hand him a treat. Mostly it was something he'd say when he was eating something he really liked.
---
This video is from 2005. Baby's feathers look a little bit seedy because he was just coming out of a molt and growing his new feathers in when this video was shot. I bought a Sony handycam for a project in 2005, and Baby got to be my test subject while I learned how to use it.