Phonetics is the study of speech sounds. It is concerned with the actual nature of the sounds and their production, as opposed to phonology which operates at the level of sound systems and linguistic units called phonemes. Discussions of meaning do not enter at this level of linguistic analysis.
The object of study of phonetics are called phones. Phones are actual speech sounds as uttered by human beings.
Phonetics has three main branches:
Of all the speech sounds that a human vocal tract can create, different languages vary considerably in the number of these sounds that they use. Languages can contain from 2 to 30 vowels and 5 to over 100 consonants (roughly, anyone know exact numbers?). The total number of phones in languages varies from as few as 11 in Rotokas (spoken in Papua New Guinea) and 12 in Hawaiian to as many as 147 in !Xu~[?] (spoken in southern Africa, in the vicinity of the Kalahari desert). These may range from familiar sounds like /t/, /s/ or /m/ to very unusual ones produced in extraordinary ways (see: clicks, phonation, airstream mechanism[?]). The English language has about 13 vowel and 26 consonant phonemes, some of which have multiple allophones. This differs from the lay definition based on the Latin alphabet, where there are 21 consonants and 5 vowels (although sometimes y and w are included as vowels).
Phonetics was studied as early as 2500 years ago in ancient India .