I recently got my first chinchilla. I have a question?

Now, I know everything about chinchillas, except for one thing. My chinchilla, Zoe, makes kind of a tooth chattering sound when she is out playing or being cuddled. It's not an aggressive chatter like a rabbit or bruxing like a rat. It is a short "che-cha" of her teeth, and she only does it when she's outside the cage. She seems happy, and she is, She's playing or falling asleep, and you will just hear this little "che-cha" What does that mean?