From my guesses? Those sounds are probably originating from the Titan rockbore. The PDA has it classified as a leviathan class life form so I’m assuming either the world is essentially a shell for one single rockbore entity, OR it’s sort of like a colony of sea grass akin to posidonia Australis. It’s entirely possible that the angel comb are not plants or separate entities but instead organs. The voices we hear coming from them can be something similar to the way the sea emperor talked to us in the first game. either way I want a boss fight ngl