Phonetic and phonological changes[edit]
Main articles: Sound change and Phonological change
The concept of sound change covers both phonetic and phonological developments.
The sociolinguist William Labov recorded the change in pronunciation in a relatively short period in the American resort of Martha's Vineyard and showed how this resulted from social tensions and processes.[4] Even in the relatively short time that broadcast media have recorded their work, one can observe the difference between the pronunciation of the newsreaders of the 1940s and the 1950s and the pronunciation of today. The greater acceptance and fashionability of regional accents in media may[original research?] also reflect a more democratic, less formal society — compare the widespread adoption of language policies.
The mapping and recording of small-scale phonological changes poses difficulties, especially as the practical technology of sound recording dates only from the 19th century. Written texts provide the main (indirect) evidence of how language sounds have changed over the centuries. But note Ferdinand de Saussure's work on postulating the existence and disappearance of laryngeals in Proto-Indo-European as an example of other methods of detecting/reconstructing sound-changes within historical linguistics.