End-to-end Transfer Learning for Speaker-independent Cross-language Speech Emotion Recognition

Data-driven models achieve successful results in Speech Emotion Recognition (SER). However, these models, which are based on general acoustic features or end-to-end approaches, show poor performance when the testing set has a different language (i.e., the cross-language setting) than the training set or when they come from a different dataset (i.e., the cross-corpus setting). To alleviate this problem, this paper presents an end-to-end Deep Neural Network (DNN) model based on transfer learning for cross-language SER. We use the wav2vec 2.0 pre-trained model to transform audio time-domain waveforms from different languages, different speakers and different recording conditions into a feature space shared by multiple languages, thereby it reduces the language variabilities in the speech features. Next, we propose a new Deep-Within-Class Co-variance Normalisation (Deep-WCCN) layer that can be inserted into the DNN model and it aims to reduce other variabilities including speaker variability, channel variability and so on. The whole model is fine-tuned in an end-to-end manner on a combined loss and is validated on datasets from three languages (i.e., English, German, Chinese). Experiment results show that our proposed method not only outperforms the baseline model that is based on common acoustic feature sets for SER in the within-language setting, but also significantly outperforms the baseline model for cross-language setting. In addition, we also experimentally validate the effectiveness of Deep-WCCN, which can further improve the model performance. Finally, to comparing the results in the recent literatures that use the same testing datasets, our proposed model shows significantly better performance than other state-of-the-art models in cross-language SER.