Emotion information from speech can effectively help robots understand speaker’s intentions in natural human-robot interaction. The human auditory system can easily track temporal dynamics of emotion by perceiving the intensity and fundamental frequency of speech, and focus on the salient emotion regions. Therefore, speech emotion recognition combined with the auditory mechanism and attention mechanism may be an effective way. Some previous studies used auditory-based static features to identify emotion while ignoring the emotion dynamics. Some other studies used attention models to capture the salient regions of emotion while ignoring cognitive continuity. To fully utilize the auditory and attention mechanism, we first investigate temporal modulation cues from auditory front-ends and then propose a joint deep learning model that combines 3D convolutions and attention-based sliding recurrent neural networks (ASRNNs) for emotion recognition. Our experiments on the IEMOCAP and MSP-IMPROV datasets indicate that the proposed method can be effectively used to recognize the emotions of speech from temporal modulation cues. The subjective evaluation shows that the attention patterns of the attention model are basically consistent with human behaviors in recognizing the emotions.

In one study on vocal emotion recognition using noise-vocoded speech (NVS), the high similarities between modulation spectral features (MSFs) and the results of vocal-emotion-recognition experiments indicated that MSFs contribute to vocal emotion recognition in a clean environment (with no noise and no reverberation). Other studies also clarified that vocal emotion recognition using NVS is not affected by noisy reverberant environments (signal-to-noise ratio is greater than 10 dB and reverberation time is less than 1.0 s). However, the contribution of MSFs to vocal emotion recognition in noisy reverberant environments is still unclear. We aimed to clarify whether MSFs can be used to explain the vocal-emotion-recognition results in noisy reverberant environments. We analyzed the results of vocal-emotion-recognition experiments and used an auditory-based modulation filterbank to calculate the modulation spectrograms of NVS. We then extracted ten MSFs as higher-order statistics of modulation spectrograms. As shown from the relationship between MSFs and vocal-emotion-recognition results, except for extremely high noisy reverberant environments, there were high similarities between MSFs and the vocal emotion recognition results in noisy reverberant environments, which indicates that MSFs can be used to explain such results in noisy reverberant environments. We also found that there are two common MSFs (MSKT${}_k$ (modulation spectral kurtosis) and MSTL${}_k$ (modulation spectral tilt)) that contribute to vocal emotion recognition in all daily environments.

Hence, developing a corpus for speech emotion recognition (SER) in the target domain is significant; however, this is time-consuming and cost-intensive. In this study, we aim to fully use a partially-labeled corpus in the target domain (target corpus) with the help of an existing fully-labeled corpus (common corpus). To this end, we proposed a method that leverages domain adversarial multi-task learning to reconcile the definitions of emotion classes across domains and noisy student training to utilize unlabeled data. Our experimental results demonstrated that the proposed method improved the SER performance in the target domain when the target corpus was small in size and imbalanced in classes. Furthermore, performance on the common corpus was not deteriorated by the proposed method.