Editing Speech synthesis (section)

==== Diphone synthesis ====

Diphone synthesis uses a minimal speech database containing all the [[diphone]]s (sound-to-sound transitions) occurring in a language. The number of diphones depends on the [[phonotactics]] of the language: for example, Spanish has about 800 diphones, and German about 2500. In diphone synthesis, only one example of each diphone is contained in the speech database. At runtime, the target [[prosody (linguistics)|prosody]] of a sentence is superimposed on these minimal units by means of [[digital signal processing]] techniques such as [[linear predictive coding]], [[PSOLA]]<ref>{{cite web|title=Pitch-Synchronous Overlap and Add (PSOLA) Synthesis|url=http://www.fon.hum.uva.nl/praat/manual/PSOLA.html|url-status=dead|archive-url=https://web.archive.org/web/20070222180903/http://www.fon.hum.uva.nl/praat/manual/PSOLA.html|archive-date=February 22, 2007|access-date=2008-05-28}}</ref> or [[MBROLA]].<ref>T. Dutoit, V. Pagel, N. Pierret, F. Bataille, O. van der Vrecken. [http://ai2-s2-pdfs.s3.amazonaws.com/7b1f/dadf05b8f968a5b361f6f82852ade62c8010.pdf The MBROLA Project: Towards a set of high quality speech synthesizers of use for non commercial purposes]. ''ICSLP Proceedings'', 1996.</ref> or more recent techniques such as pitch modification in the source domain using [[discrete cosine transform]].<ref name="Muralishankar2004">{{cite journal | last1 = Muralishankar | first1 = R. | last2 = Ramakrishnan | first2 = A. G. | last3 = Prathibha | first3 = P. | date = February 2004 | title = Modification of Pitch using DCT in the Source Domain | journal = Speech Communication | volume = 42 | issue = 2 | pages = 143–154 | doi=10.1016/j.specom.2003.05.001}}</ref> Diphone synthesis suffers from the sonic glitches of concatenative synthesis and the robotic-sounding nature of formant synthesis, and has few of the advantages of either approach other than small size. As such, its use in commercial applications is declining,{{Citation needed|date=January 2012}} although it continues to be used in research because there are a number of freely available software implementations. An early example of Diphone synthesis is a teaching robot, [[Leachim (Robot)|Leachim]], that was invented by [[Michael J. Freeman]].<ref>{{Cite news|url=http://content.time.com/time/magazine/article/0,9171,904056,00.html|title=Education: Marvel of The Bronx|date=1974-04-01|magazine=Time|access-date=2019-05-28|language=en-US|issn=0040-781X}}</ref> Leachim contained information regarding class curricular and certain biographical information about the students whom it was programmed to teach.<ref>{{Cite web|url=http://cyberneticzoo.com/robots/1960-rudy-the-robot-michael-freeman-american/|title=1960 - Rudy the Robot - Michael Freeman (American)|date=2010-09-13|website=cyberneticzoo.com|language=en-US|access-date=2019-05-23}}</ref> It was tested in a fourth grade classroom in [[The Bronx|the Bronx, New York]].<ref>{{Cite book|url=https://books.google.com/books?id=bNECAAAAMBAJ&q=Leachim+Michael+Freeman&pg=PA40|title=New York Magazine|date=1979-07-30|publisher=New York Media, LLC|language=en}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=_QJmAAAAMAAJ&q=leachim|title=The Futurist|date=1978|publisher=World Future Society.|pages=359, 360, 361|language=en}}</ref>