I've read in behavioral books that cats do this while hunting. I've only ever seen it when my cats spot a rodent. Weird to see them do it at other times.
Mine does it too.
From what I read they think it's some kind of hissing and they are calling you on your challenge or they are scolding you for inappropriate behavior.
I also read other theories why they make that chattering noise: it can be either from frustration (my cat does that when she's behind a window and she sees a bird and really wants to go out and hunt it), or from a surge of adrenaline (hunter instincts).
With all the cats I've ever had and all the explanations I've been given they mostly do it while hunting. My cats used to do it while staring at flies or birds it couldn't get to. So it's strange it did it to a sneeze