A study of pronunciation verification in a speech therapy application

Techniques are presented for detecting phoneme level mispro-nunciations in utterances obtained from a population of impaired children speakers. The intended application of these approaches is to use the resulting confidence measures to provide feedback to patients concerning the quality of pronunciations in utterances arising within interactive speech therapy sessions. The pronunciation verification scenario involves presenting utterances of known words to a pho-netic decoder and generating confusion networks from the resulting phone lattices. Confidence measures are derived from the posterior probabilities obtained from the confusion networks. Phoneme level mispronunciation detection performance was significantly improved with respect to a baseline system by optimizing acoustic models and pronunciation models in the phonetic decoder and applying a non-linear mapping to the confusion network posteriors. Index Terms — confidence measure, speech therapy 1