A CALL system using speech recognition to train the pronunciation of Japanese long vowels, the mora nasal and mora obstruents

We developed a CALL (computer-aided language learning) system for teaching the pronunciation of Japanese long vowels, the mora nasal and mora obstruents to nonnative speakers of Japanese. Long vowels and short vowels are spectrally almost identical but their phone durations differ significantly. Similar conditions exist between mora nasals and non-mora nasals, and between mora and non-mora obstruents. Our system uses speech recognition to measure the durations of each phone and compares them with distributions of native speakers while correcting for different speech rates. Results show that learners quickly capture the relevant duration cues. The amount of learning time spent on acquiring these durational skills is well within the time constraints of TJSL (teaching Japanese as a second language) curricula.