Development of a computer-assisted language learning system utilizing a speaker adaptation and a grammatical error modeling

点击翻译按钮获取中文摘要

1. Improvement of Pronunciation EvaluationWe developed a method to detect pronunciation mistakes made by a foreign language learner by applying a speech recognition technology. We focused on the following two targets: learning of English by Japanese native speakers and learning of Japanese by Korean native speakers. To improve the accuracy of detection of mispronunciations, we developed a bilingual speaker adaptation method to adapt both of English and Japanese HMMs to the learner. To solve a problem that the strictness of the detection of mispronunciations depends on the linguistic context of the pronunciation, we developed a method of detecting mispronunciations using a decision tree, which gave a detection accuracy of more than 90% on English utterances made by Japanese native speakers.2. Evaluation of Intonation and RhythmIn addition to the detection of mispronunciations, we developed methods to evaluate intonation and rhythm of the English utterances. We found that the log F0, log power and their derivatives were good features for the evaluation of intonation. To adjust the strictness of intonation evaluation from word to word, we introduced a method to estimate the word importance factors using a decision tree. We also found that a word duration ratio was a good feature for rhythm evaluation.3. Development of an interactive CALL systemWe developed a method of detecting grammatical errors from utterances of a learner for the application to an interactive CALL system that enables for a learner to learn a foreign language through dialogues with a computer. As for the learning of Japanese, we developed a method to recognize the learner's speech using a finite state automaton to which grammatical error rules were applied. As for the learning of English, we developed a method to use an n-gram language model trained from a corpus that was automatically generated using the grammatical error rules.