This is a classic example of a dog with good intentions. Many dogs have the natural urge to protect members of their family, especially those who cannot protect themselves. He hears this sound and obviously thinks it is something dangerous. His first instinct is to get defensive. Instead of running away, he decides to protect his baby sister.
His ‘parents’ in the video note that the dog was in no way harmed in this video. In fact, one is a professional dog groomer and insists that both dog and baby receive excellent care. What did you think of the dog’s reaction?