  Speech emotion recognition is a challenging task in speech processing field.
For this reason, feature extraction process has a crucial importance to
demonstrate and process the speech signals. In this work, we represent a model,
which feeds raw audio files directly into the deep neural networks without any
feature extraction stage for the recognition of emotions utilizing six
different data sets, EMO-DB, RAVDESS, TESS, CREMA, SAVEE, and TESS+RAVDESS. To
demonstrate the contribution of proposed model, the performance of traditional
feature extraction techniques namely, mel-scale spectogram, mel-frequency
cepstral coefficients, are blended with machine learning algorithms, ensemble
learning methods, deep and hybrid deep learning techniques. Support vector
machine, decision tree, naive Bayes, random forests models are evaluated as
machine learning algorithms while majority voting and stacking methods are
assessed as ensemble learning techniques. Moreover, convolutional neural
networks, long short-term memory networks, and hybrid CNN- LSTM model are
evaluated as deep learning techniques and compared with machine learning and
ensemble learning methods. To demonstrate the effectiveness of proposed model,
the comparison with state-of-the-art studies are carried out. Based on the
experiment results, CNN model excels existent approaches with 95.86% of
accuracy for TESS+RAVDESS data set using raw audio files, thence determining
the new state-of-the-art. The proposed model performs 90.34% of accuracy for
EMO-DB with CNN model, 90.42% of accuracy for RAVDESS with CNN model, 99.48% of
accuracy for TESS with LSTM model, 69.72% of accuracy for CREMA with CNN model,
85.76% of accuracy for SAVEE with CNN model in speaker-independent audio
categorization problems.
