Transformer Based End-to-End Mispronunciation Detection and Diagnosis.

This paper introduces two Transformer-based architectures for Mispronunciation Detection and Diagnosis (MDD). The first Transformer architecture (T-1) is a standard setup with an encoder, a decoder, a projection part and the Cross Entropy (CE) loss. T-1 takes in Mel-Frequency Cepstral Coefficients (MFCC) as input. The second architecture (T-2) is based on wav2vec 2.0, a pretraining framework. T-2 is composed of a CNN feature encoder, several Transformer blocks capturing contextual speech representations, a projection part and the Connectionist Temporal Classification (CTC) loss. Unlike T-1, T-2 takes in raw audio data as input. Both models are trained in an end-to-end manner. Experiments are conducted on the CU-CHLOE corpus, where T-1 achieves a Phone Error Rate (PER) of 8.69% and F-measure of 77.23%; and T-2 achieves a PER of 5.97% and F-measure of 80.98 %. Both models significantly outperform the previously proposed AGPM and CNN-RNN-CTC models, with PERs at 11.1% and 12.1% respectively, and F-measures at 72.61% and 74.65 % respectively.