Prosody Analysis of L2 English for Naturalness Evaluation Through Speech Modification

This study investigates how different prosodic features affect native speakers' naturalness judgement of L2 English speech by Chinese students. Through subjective judgment by native speakers and objectively measured prosodic features, timing and pitch related prosodic features, as well as segmental goodness of pronunciation have been found to play key roles in native speakers' perception of naturalness. In order to eliminate segmental factors, we used accent conversion techniques that modify native reference speech with learners' erroneous prosodic cues without altering segmental properties. Experimental results show that without interference of segmental factors, both timing and pitch features affect naturalness of L2 speech. Timing plays a more crucial role in naturalness than pitch. Accent modification that corrects timing or pitch errors can improve naturalness of the speech.