Dogs communicate pleasure, happiness, excitement, and affiliation through their vocalizations. The most common sounds of pleasure are moans and sighs, although dogs also use whines and growls to communicate happiness.
Low-pitched moans are very common in puppies and are signs of contentment. Puppies moan when they are in close contact to their littermates, their mother, or their humans. Another sound of contentment is the sigh, usually accompanied by the dog lying down with its head on its forepaws. When the sigh is combined with half-closed eyes, it communicates pleasure; with fully open eyes, it communicates disappointment: “I guess you are not going to play with me.”
Although often considered signs of distress, whines can also be used to communicate happiness and excitement. The difference is that a whine used to communicate distress rises in pitch toward the end of the sound, whereas a whine communicating excitement either drops in pitch toward the end of the sound or does not change in pitch.
Similarly, there are growls that are not used as warnings or threats but are used to communicate play. Such growls are noisy and medium-pitched, with no low rumbling (like that heard in warning growls) and no signs of teeth.
Compared to people, dogs have a much clearer understanding of the difference between play-growls and threatening growls. When researchers played different types of recorded growls over a speaker in front of a desirable bone, dogs avoided the bone in the presence of warning growls, but grabbed it in the presence of play-growls.
The quintessential communication of affiliation is the howl. Howling in dogs seems to be a behavior similar to that in wolves. A dog howling by itself is communicating, “I want my pack.” Such a howl is often contagious.
Dogs make sounds both intentionally and unintentionally, and they all have certain meanings. Just because we do not understand all of the wonderful variety of sounds that dogs vocalize does not mean that dogs are not doing their best to communicate with us.