Orthography-based pronunciation scoring for better CAPT feedback

We establish the viability of a streamlined architecture for pedagogically appropriate computer assisted pronunciation training (CAPT), to give second language learners automatic feedback about their mispronunciations. This takes advantage of end-to-end speech recognition models to detect mispronunciation in audio segments that correspond directly to orthographic letters, in contrast to standard mispronunciation detection using phone representations. Results in a classification task show the potential for similar sensitivity to non-nativelike phonetic errors in grapheme-aligned segments as in phone-aligned segments. Advantages of this approach over phone-based pronunciation scoring can include providing naturally comprehensible (orthographic, not phonemic) feedback to learners, being inherently open-vocabulary in the target language, and evaluating pronunciations with reference to a full range of target-language acoustic variants rather than a prespecified canonical phone sequence.