My baby growls. I don't know where she learned it, but it is the most common sound in her communication. It is closely followed in frequency by the raspberry.
It makes me laugh because I think of when Isaac was a baby and he had this high-pitched coo. He even sounded a little bit - forgive me Isaac - girly.
Now I have this beautiful little girl all dressed in bows and lace and she growls and spits.