Phonetics is concerned with describing the speech sounds that occur in the languages of the world. We want to know what these sounds are, how they fall into patterns, and how they change in different circumstance ... The first job of a phonetician is ... to try to find out what people are doing when they are talking and when they are listening to speech.
Peter Ladefoged
Knowledge of a language includes knowledge of morphemes, word, phrases, and sentences. It also includes knowing what sounds are in the language and how they may be 'strung' together to form these meaningful unit. Although the sounds of French or Xhosa or Arrernte are uninterpretable to someone who does not speak those language, and although there may be some sounds in one language that are not in another, the sounds of all the languages of the world together constitute a limited set of all the sounds that can be produced by the human vocal tract.
