When I heard that dialogue referring to an old man’s voice, I immediately related that to the Hive Mind (obviously, that’s a very general statement. Allow me to explain). If we go back to the fact that the monsters understand and speak our language, we need to simply ask: how?
My theory is they didn’t understand until Kala. The very second that Kala’s mind connected with the Hive Mind, that opened a communication channel. Instantly, Kala and this Hive Mind had access to each other’s minds. It could be possible that, since the Hive Mind is so adept at controlling multiple beings at once (ie. The Monsters), it can read all of the data stored within Kala’s mind and has immediate access to it. Kala probably doesn’t have this ability because she lacks the experience. It is possible that Kala has access to all of the Hive Mind’s information, but does not quite know how to access it. Thus, Kala only knows what this Hive Mind is directly sending to her and wants her to know.
Still following? Coolio. Now, when analyzing an unconscious Kala, we learn through Abe that she is chanting, working through complex mathematics, and even speaking. But, she is not speaking. Now I know, “Wait, you just said she was speaking in her sleep”. I don’t believe this to be the case. Kala is connected to the Hive Mind. This means that there is probably no way for either the Hive Mind or Kala to block communication now that they have been connected. Anything that the Hive Mind actively “broadcasts” to the monsters, also goes to Kala.
Anything that the Hive Mind actively “broadcasts” to the monsters, also goes to Kala.
The Mathematics: this is likely the Hive Mind going through the calculations to send the transport pods (eggs) to our dimension through Cherenkov Space.
The Chanting: what is a chant? “A repeated rhythmic phrase, typically one shouted or sung in unison by a crowd”. This could be proof that the monsters are ritualistic, thus bringing a spiritual, superstitious card to the table. Maybe even the Monsters have their own belief system.
The Voice: this may just be the actual voice of the Hive Mind portrayed through Kala’s physical form. When the Mind speaks, it does so by broadcasting a message to all of its connected beings. Kala, unconsciously, speaks the information that is broadcasted to her.
Edit: Omg sorry for the wall of text! I just typed this out quickly.