Wolves rarely bark except as an alarm, but most dogs bark often and everywhere. There are alarm barks, "let-me-outside" barks, "I-want-to-play" barks, and more. All this barking may be a result of early breeding of the first dogs where humans selected for effective guarders -- more specifically, the noisiest!
Recent research has discovered distinct vocalizations made by playing dogs. Could these sounds be dogs laughing? When researchers play the sounds for a group of dogs at rest, some of the dogs will grab toys and try to get their buddies to play.