Let's try something a bit less obvious then. The astronaut Rinoa passes when heading out to Adel's tomb? He says something like "Huh? Who is that?", which is a question of identity. The voice is "heard" (pervasive), although voices can't really be heard in a vacuum (immaterial) environment.

You only hear him speak once, I think, unless that's Laguna. I don't rightly remember. I guess it could be questioned if he really wants an answer, since he just keeps on going instead of trying to find out.