PHONETICS: THE SOUNDS OF LANGUAGE
Phonetic transcription & the International Phonetic Alphabet
Since the sixteenth century, efforts have been made to devise a universal system for transcribing the sounds of speech. The best known system the International Phonetic Alphabet (IPA) has been developing since 1888.
This system developed by the International Phonetic Association (website: http://www2.arts.gla.ac.uk/IPA/ipa.html) attempts to represent each sound of human speech with a single symbol.
These symbols are enclosed in brackets [ ] to indicate that the transcription is phonetic and does not represent the spelling system of a particular language.
e.g. the sound spelled th in English ‘this’ is transcribed as 
IPA uses this symbol to represent this sound in whichever language it is heard.
Also, though English uses the same spelling to represent the first sound in theatre, as it is pronounced different, IPA represents it with a different symbol – 
The use of a standard phonetic alphabet enables linguists to transcribe languages constantly and accurately.
Units of Representation & Segments
When you hear a language for the first time it is often difficult to break up the flow of speech into individual units of production.
Even when hearing our own language spoken, we do not focus attention on individual sounds as much as we do on the meanings of words, phrases and sentences.
Many alphabets, including the IPA, represent speech in the form of segments, or individual speech sounds like [a], [o], [p], [m] or [g].
Segments are composed of smaller subunits called features such as ‘nasal’, which characterizes consonants like [m] and [n] as opposed to [b] and [d] .
Even though features are not usually represented in writing systems, they are important elements of linguistic representation.
Features represent individual aspects of articulatory control or acoustic effects produced by articulation.
There are several kinds of evidence that suggest that speakers have the linguistic knowledge that makes it possible to break down a stream of speech into sound segments.
Errors in speech production provide one kind of evidence for the existence of segments.
e.g. slips of the tongue such as 
, for 
and
she sells for sea shells
This suggests that segments are individual units of linguistic structure and thus should be represented individually in a system of transcription.
