Pronunciation quality is automatically evaluated for an utterance of speech based on one or more pronunciation scores. One type of pronunciation score is based on duration of acoustic units. Examples of acoustic units include phones and syllables. Another type of pronunciation score is based on a posterior...http://www.google.de/patents/US6055498?utm_source=gb-gplus-sharePatent US6055498 - Method and apparatus for automatic text-independent grading of pronunciation for language instruction
