Editing Speech synthesis (section)

==== Domain-specific synthesis ====

Domain-specific synthesis concatenates prerecorded words and phrases to create complete utterances. It is used in applications where the variety of texts the system will output is limited to a particular domain, like transit schedule announcements or weather reports.<ref>[[Lori Lamel|L.F. Lamel]], J.L. Gauvain, B. Prouts, C. Bouhier, R. Boesch. [http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.53.6101&rep=rep1&type=pdf Generation and Synthesis of Broadcast Messages], ''Proceedings ESCA-NATO Workshop and Applications of Speech Technology'', September 1993.</ref> The technology is very simple to implement, and has been in commercial use for a long time, in devices like talking clocks and calculators. The level of naturalness of these systems can be very high because the variety of sentence types is limited, and they closely match the prosody and intonation of the original recordings.{{Citation needed|date=February 2007}}

Because these systems are limited by the words and phrases in their databases, they are not general-purpose and can only synthesize the combinations of words and phrases with which they have been preprogrammed. The blending of words within naturally spoken language however can still cause problems unless the many variations are taken into account. For example, in [[rhotic and non-rhotic accents|non-rhotic]] dialects of English the ''"r"'' in words like ''"clear"'' {{IPA|/ˈklɪə/}} is usually only pronounced when the following word has a vowel as its first letter (e.g. ''"clear out"'' is realized as {{IPA|/ˌklɪəɹˈʌʊt/}}). Likewise in [[French language|French]], many final consonants become no longer silent if followed by a word that begins with a vowel, an effect called [[Liaison (French)|liaison]]. This [[alternation (linguistics)|alternation]] cannot be reproduced by a simple word-concatenation system, which would require additional complexity to be [[context-sensitive grammar|context-sensitive]].