Very cool sound design detail! I saw an interview where James Ortiz talked about trying to give Rocky an emotional character arc, something that was absent in the book and script. He talked about telling the story of trauma recovery physically through Rocky's body language. How he wanted the audience to feel Rocky's journey from shell-shocked to feeling comfortable in his own body again.
And that's reflected in the sound design with Rocky's echolocation noise.
He makes this sound when he's trying to "look" closely at something, usually objects. The cool thing is, he also does it when he feels insecure. Whenever he gets vulnerable and uncomfortable he pings this noise at Grace. It's like looking really closely at someone because you're anxious to know what they're thinking.
He goes from doing it before and after every sentence, to less and less as they get familiar with each other. He's suddenly doing it non-stop again for the whole one-way trip conversation, when Grace is actively hiding his emotions from him. It doesn't show up again after that until the end when he hesitates before calling Grace "brave".
Really good detail.
