Since the day Rinn figured out he could make noise, he has been making this warbling, chirpy sound by way of rolling his tongue. Initially it resembled that infamous "click" used by the Predator to communicate and I was constantly terrified of my own infant. Now that Rinn understands the range of his voice it's slightly less intimidating, which I think he figured out when I stopped recoiling in fear as he approached. To maintain his dominance he now slaps aggressively and has ridiculously accurate aim when throwing blocks and television remotes.
Combine the warble with the click consonants he must've picked up on his travels to South Africa and he's well on his way to creating his own language.