Vocal, articulate, oral can all mean uttered by the voice or having to do with utterance.
Vocal implies the use of voice, but not necessarily of speech or language; thus, vocal sounds are sounds produced by a creature that has vocal organs; vocal music is contrasted with instrumental music because the musical tones are produced by the voice rather than by a musical instrument.
Articulate implies the use of distinct intelligible language; thus, speech is the uttering of articulate sounds; articulate cries are those that are expressed in meaningful words rather than in meaningless sounds .
Oral implies the use of the voice rather than the hand (as in writing or typing) in communicating (as thoughts, wishes, orders, questions, or answers).