Automatic intonation assessment for computer aided language learning

In this paper the nature and relevance of the information provided by intonation is discussed in the framework of second language learning. As a consequence, an automatic intonation assessment system for second language learning is proposed based on a top-down scheme. A stress assessment system is also presented by combining intonation and energy contour estimation. The utterance pronounced by the student is directly compared with a reference one. The trend similarity of intonation and energy contours are compared frame-by-frame by using DTW alignment. Moreover the robustness of the alignment provided by the DTW algorithm to microphone, speaker and quality pronunciation mismatch is addressed. The intonation assessment system gives an averaged subjective–objective score correlation as high as 0.88. The stress assessment evaluation system gives an EER equal to 21.5%, which in turn is similar to the error observed in phonetic quality evaluation schemes. These results suggest that the proposed systems could be employed in real applications. Finally, the schemes presented here are text- and language-independent due to the fact that the reference utterance text-transcription and language are not required.