Phonetic transcription (also known as phonetic script or phonetic notation) is the visual representation of speech sounds (or phones) by means of symbols. The most common type of phonetic transcription uses a phonetic alphabet, such as the International Phonetic Alphabet. The pronunciation of words in all languages changes over time. However, their written forms (orthography) are often not modified to take account of such changes, and do not accurately represent the pronunciation. Pronunciation can also vary greatly among dialects of a language. Standard orthography in some languages, such as English and Tibetan, is often irregular and makes it difficult to predict pronunciation from spelling
Phonetic transcription may be used to transcribe the phonemes of a language, or it may go further and specify their precise phonetic realization. In all systems of transcription there is a distinction between broad transcription and narrow transcription. Broad transcription indicates only the most noticeable phonetic features of an utterance, whereas narrow transcription encodes more information about the phonetic characteristics of the allophones in the utterance. The difference between broad and narrow is a continuum, but the difference between phonemic and phonetic transcription is usually treated as a binary distinction. Phonemic transcription is a particular form of broad transcription which disregards all allophonic difference; as the name implies, it is not really a phonetic transcription at all (though at times it may coincide with one), but a representation of phonemic structure. A transcription which includes some allophonic detail but is closely linked to the phonemic structure of an utterance is called an allophonic transcription.
The advantage of the narrow transcription is that it can help learners to produce exactly the right sound, and allows linguists to make detailed analyses of language variation.[ The disadvantage is that a narrow transcription is rarely representative of all speakers of a language. While most Americans, Canadians and Australians would pronounce the /t/ of little as a tap [ɾ], many speakers in southern England would pronounce /t/ as [ʔ] (a glottal stop; t-glottalization) and/or the second /l/ as a vowel resembling [ʊ] (L-vocalization), possibly yielding