Always called that "churdles". Same thing I bet though, sounds just like a tribble. And yeah, when he's content he does that.Our cat Clyde often trills when he is active (playing, running, jumping). His trill reminds me of tribbles from Star Trek.
Ah, this must be what Phoenix does every morning at 0400... her way of telling me it's time to get up and make breakfast. She keeps it up for awhile too, since I refuse to get up at that hour, especially if I have a hangover. When I finally haul myself out of bed and start getting dressed, she does it again, rubbing against my legs and generally getting underfoot as I alternately pull clothes on and pet her. Once we're all in the kitchen, the trilling changes to straight-up meowing, as if---AS IF---she's starving, LOL. Neither one of the other kittehs makes this trilling noise, only Phoenix, so I always know it's her in the dark. It's actually an agreeable sound as I get dressed... not so much at 0400.Wow, I had no idea there was a name for this.