In The Order Of The Stick, there is a main character named Vaarsuvius who's ambiguous sex is a running joke. Between her voluminous robes and the Elves' natural androgyny, it is impossible to tell if he is a guy or a girl. It's also impossible to tell whether it is married to a guy or a girl because his spouse is just as androgynous, and the Elven words for "mom" and "dad" are translated as "parent" and "other parent". Heck, their kids are adopted, so they could be a gay couple. That doesn't stop other characters from assuming that she is one or the other. The ones who should know best (fiends from the lower planes who have a time-share on Vaarsuvius' soul) admit that even they don't have a clue. The best I can do when talking about him is using Pyro-pronouns.

So let's just assume that Noble 6 is so classified, even his biological sex is covered in black ink, and everyone is making their best guess at what he/she sounds like.