<P> To produce any kind of sound, there must be movement of air . To produce sounds that people today can interpret as words, the movement of air must pass through the vocal chords, up through the throat and, into the mouth or nose to then leave the body . Different sounds are formed by different positions of the mouth--or, as linguists call it, "the oral cavity" (to distinguish it from the nasal cavity). </P> <P> Sounds of all languages fall under two categories: Consonants and Vowels . </P> <P> Consonants are produced with some form of restriction or closing in the vocal tract that hinders the airflow from the lungs . Consonants are classified according to where in the vocal tract the airflow has been restricted . This is also known as the place of articulation . </P> <P> Movement of the tongue and lips can create these constrictions and by forming the oral cavity in different ways, different sounds can be produced . </P>

Speech sounds made with restricted airflow are known as