A.C.
She's simply found a new sound that she finds interesting. You'll find she'll go through a TON of weird, strange and down right hysterical sounds while she's still finding her voice.
Some of the sounds my kids made as they progressed were so freakin funny I wish I'd had a video camera to send in to America's Funniest Home Videos cause I swear I literally rolled on the floor laughing at some of them.