Our goal is to develop a voice-interactive CALL system which enables language learners to practice words, phrases, and grammars interactively. Such a system must be able to recognize learner's utterances correctly. To enable the recognition of utterances containing grammatical mistakes, we used an n-gram language model trained from generated text. The proposed model achieved recognition performance similar to that of a language model based on a finite-state automaton and manual error rules. We then introduced two error correction techniques to improve recognition performance. One method used the Levenshtein distance between the target sentence and the recognized sentence. The other method used an error-corrective model based on POS n-gram features. The experimental results showed that both methods were able to improve recognition performance.
Bibliographic reference. Ito, Akinori / Tsutsui, Ryohei / Makino, Shozo / Suzuki, Motoyuki (2008): "Recognition of English utterances with grammatical and lexical mistakes for dialogue-based CALL system", In INTERSPEECH-2008, 2819-2822.