The burble is a combination of a meow, purr, and growl. There is no specific explanation for this sound, but it can mean the cat feels happy, has seen something interesting, or simply wants to say ...
Lucas doesn't meow exactly — it's most of a chirp ... However, you should keep an eye on your cat. Purring can also be a sign that they're scared, sick, or in pain. Chirping, like Lucas does ...