In this paper the task of emotion recognition from speech is considered. Proposed approach uses deep recurrent neural network trained on a sequence of acoustic features calculated over small speech intervals. At the same time special probabilistic-nature CTC loss function allows to consider long utterances containing both emotional and neutral parts. The effectiveness of such an approach is shown in two ways. Firstly, the comparison with recent advances in this field is carried out. Secondly, human performance on the same task is measured. Both criteria show the high quality of the proposed method.
Abstract Speech emotion recognition is a challenging problem partly be-cause it is unclear what features are effective for the task. Inthis paper we propose to utilize deep neural networks (DNNs)to extract high level features from raw data and show that theyare effective for speech emotion recognition. We ﬁrst producean emotion state probability distribution for each speech seg-ment using DNNs. We then construct utterance-level featuresfrom segment-level probability distributions. These utterance-level features are then fed into an extreme learning machine(ELM),aspecialsimpleandefﬁcientsingle-hidden-layer neuralnetwork, to identify utterance-level emotions. The experimen-tal results demonstrate that the proposed approach effectivelylearns emotional information from low-level features and leadsto 20 relative accuracy improvement compared to the state-of-the-art approaches. IndexTerms : Emotion recognition, Deep neural networks, Ex-treme learning machine 1. Introduction Despite the great progress made in artiﬁcial intelligence, weare still far from being able to naturally interact with machines,partly because machines do not understand our emotion states.Recently, speech emotion recognition, which aims to recognizeemotion states from speech signals, has been drawing increas-ing attention. Speech emotion recognition is a very challengingtask of which extracting effective emotional features is an openquestion [1, 2].Adeep neural network (DNN) is afeed-forward neural net-work that has more than one hidden layers between its inputsand outputs. It is capable of learning high-level representationfrom the raw features and effectively classifying data [3, 4].With sufﬁcient training data and appropriate training strategies,DNNs perform very well in many machine learning tasks (e.g.,speech recognition [5]).Feature analysis in emotion recognition is much less stud-ied than that in speech recognition. Most previous studies em-pirically chose features for emotion classiﬁcation. In this study,aDNNtakesasinputtheconventional acousticfeatureswithinaspeechsegmentandproducessegment-levelemotionstateprob-ability distributions, from which utterance-level features areconstructed and used to determine the utterance-level emotionstate. Since the segment-level outputs already provide consid-erable emotional information and the utterance-level classiﬁca- This paper presents a speech emotion recognition system using a recurrent neural network (RNN) model trained by an efficient learning algorithm. The proposed system takes into account the long-range context effect and the uncertainty of emotional label expressions. To extract high-level representation of emotional states with regard to its temporal dynamics, a powerful learning method with a bidirectional long short-term memory (BLSTM) model is adopted. To overcome the uncertainty of emotional labels, such that all frames in the same utterance are mapped into the same emotional label, it is assumed that the label of each frame is regarded as a sequence of random variables. Then, the sequences are trained by the proposed learning algorithm. The weighted accuracy of the proposed emotion recognition system is improved up to 12 compared to the DNN-ELM based emotion recognition system used as a baseline.