Manifolds Based Emotion Recognition in Speech

The paper presents an emotional speech recognition system with the analysis of manifolds of speech. Working with large volumes of high-dimensional acoustic features, the researchers confront the problem of dimensionality reduction. Unlike classical techniques, such as Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA), a new approach, named Enhanced Lipschitz Embedding (ELE) is proposed in the paper to discover the nonlinear degrees of freedom that underlie the emotional speech corpus. ELE adopts geodesic distance to preserve the intrinsic geometry at all scales of speech corpus. Based on geodesic distance estimation, ELE embeds the 64-dimensional acoustic features into a six-dimensional space in which speech data with the same emotional state are generally clustered around one plane and the data distribution feature is beneficial to emotion classification. The compressed testing data is classified into six emotional states (neutral, anger, fear, happiness, sadness and surprise) by a trained linear Support Vector Machine (SVM) system. Considering the perception constancy of humans, ELE is also investigated in terms of its ability to detect the intrinsic geometry of emotional speech corrupted by noise. The performance of the new approach is compared with the methods of feature selection by Sequential Forward Selection (SFS), PCA, LDA, Isomap and Locally Linear Embedding (LLE). Experimental results demonstrate that, compared with other methods, the proposed system gives 9%-26% relative improvement in speaker-independent emotion recognition and 5%-20% improvement in speaker-dependent recognition. Meanwhile, the proposed system shows robustness and an improvement of approximately 10% in emotion recognition accuracy when speech is corrupted by increasing noise.