Detecting Mispronunciations of L2 Learners and Providing Corrective Feedback Using Knowledge-Guided and Data-Driven Decision Trees

We propose a novel decision tree based framework to detect phonetic mispronunciations produced by L2 learners caused by using inaccurate speech attributes, such as manner and place of articulation. Compared with conventional score-based CAPT (computer assisted pronunciation training) systems, our proposed framework has three advantages: (1) each mispronunciation in a tree can be interpreted and communicated to the L2 learners by traversing the corresponding path from a leaf node to the root node; (2) corrective feedback based on speech attribute features, which are directly used to describe how consonants and vowels are produced using related articulators, can be provided to the L2 learners; and (3) by building the phone-dependent decision tree, the relative importance of the speech attribute features of a target phone can be automatically learned and used to distinguish itself from other phones. This information can provide L2 learners speech attribute feedback that is ranked in order of importance. In addition to the abovementioned advantages, experimental results confirm that the proposed approach can detect most pronunciation errors and provide accurate diagnostic feedback.