Yup. That's just their pissed off noise. I wish mine would make a noise sometime.. He/She's never 'said' anything! Doesn't even try to lunge at my fingers like they're edible. Trevor actually really enjoys getting misted. Even if he's asleep, he kind of starts awake, then is like 'Oh, okay, I like the rain' and goes back to sleep.
That's right, I'm complaining about having a pet that doesn't grumble or attack when I mess with it.