Analysis of and feedback on phonetic features in pronunciation training with a virtual teacher

Pronunciation errors may be caused by several different deviations from the target, such as voicing, intonation, insertions or deletions of segments, or that the articulators are placed incorrectly. Computer-animated pronunciation teachers could potentially provide important assistance on correcting all these types of deviations, but they have an additional benefit for articulatory errors. By making parts of the face transparent, they can show the correct position and shape of the tongue and provide audiovisual feedback on how to change erroneous articulations. Such a scenario however requires firstly that the learner's current articulation can be estimated with precision and secondly that the learner is able to imitate the articulatory changes suggested in the audiovisual feedback. This article discusses both these aspects, with one experiment on estimating the important articulatory features from a speaker through acoustic-to-articulatory inversion and one user test with a virtual pronunciation teacher, in which the articulatory changes made by seven learners who receive audiovisual feedback are monitored using ultrasound imaging.QC 20120416