Phonetics is the study of human sounds, divided into articulatory phonetics (production), acoustic phonetics (transmission), and auditive phonetics (perception). There are approximately 44 sounds in English, which can be divided into consonants and vowels. Consonants are characterized by place of articulation, manner of articulation, and whether they are voiced or voiceless. Vowels are located on a vowel quadrilateral diagram according to their actual sound values.