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Monitoring and analysis of human sentiments is currently one of the hottest research topics in the field of human-computer interaction, having many applications. However, in order to become practical in daily life, sentiment recognition techniques should analyze data collected in an unobtrusive way. For this reason, analyzing audio signals of human speech (as opposed to say biometrics) is considered key to potential emotion recognition systems. In this work, we expand upon previous efforts to analyze speech signals using computer vision techniques on their spectrograms. In particular, we utilize ORB descriptors on keypoints distributed on a regular grid over the spectrogram to obtain an intermediate representation. Firstly, a technique similar to Bag-of-Visual-Words (BoVW) is used, where a visual vocabulary is created by clustering keypoint descriptors, but instead a soft candidacy score is used to construct the histogram descriptors of the signal. Furthermore, a technique which takes into account the temporal structure of the spectrograms is examined, allowing for effective model regularization. Both of these techniques are evaluated in several popular emotion recognition datasets, with results indicating an improvement over the simple BoVW method.

In this work, we examine the process of Tropical Polynomial Division, a geometric method which seeks to emulate the division of regular polynomials, when applied to those of the max-plus semiring. This is done via the approximation of the Newton Polytope of the dividend polynomial by that of the divisor. This process is afterwards generalized and applied in the context of neural networks with ReLU activations. In particular, we make use of the intuition it provides, in order to minimize a two-layer fully connected network, trained for a binary classification problem. This method is later evaluated on a variety of experiments, demonstrating its capability to approximate a network, with minimal loss in performance.