One question was it ever stated why Randolf can hear the voices, like does he have some sort of connection to the hospital incident or is it just because he's insane?
It was indirectly stated.
[spoiler]The entire city of Inganock chose to not hear the 41 voices because they didn't want to be reminded of the disaster any more, and it was this denial that they later mistook for insanity. Randolph, as the only sane man in the city (or the only insane man, take your pick), is the only one who chose to keep listening to them. Not that he's particularly responsive...
Of course he's not the only character who can hear them, so to avoid confusion:
Iru was outside the City at the time, so he never had to make a choice one way or the other, and in many respects remains an outsider.
Kia and Lemure Lemure are Stolen Ones so they also don't count as citizens who had to make the choice. If anything they're the 42nd and 43rd voices.[/spoiler]