BERT-LID: Leveraging BERT to Improve Spoken Language Identification

Language identification is a task of automatically determining the identity of a language conveyed by a spoken segment. It has a profound impact on the multilingual interoperability of an intelligent speech system. Despite language identification attaining high accuracy on medium or long utterances (>3s), the performance on short utterances (<=1s) is still far from satisfactory. We propose an effective BERT-based language identification system (BERT-LID) to improve language identification performance, especially on short-duration speech segments. To adapt BERT into the LID pipeline, we drop in a conjunction network prior to BERT to accommodate the frame-level Phonetic Posteriorgrams(PPG) derived from the frontend phone recognizer and then fine-tune the conjunction network and BERT pre-trained model together. We evaluate several variations within this piped framework, including combining BERT with CNN, LSTM, DPCNN, and RCNN. The experimental results demonstrate that the best-performing model is RCNN-BERT. Compared with the prior works, our RCNN-BERT model can improve the accuracy by about 5% on long-segment identification and 18% on short-segment identification. The outperformance of our model, especially on the short-segment task, demonstrates the applicability of our proposed BERT-based approach on language identification.