Hybrid Models for Automatic Speech Recognition: a Comparison of Classical ANN and Kernel Based Methods

Support Vector Machines (SVMs) are state-of-the-art methods for machine learning but share with more classical Artificial Neural Networks (ANNs) the difficulty of their application to input patterns of non-fixed dimension. This is the case in Automatic Speech Recognition (ASR), in which the duration of the speech utterances is variable. In this paper we have recalled the hybrid (ANN/HMM) solutions provided in the past for ANNs and applied them to SVMs performing a comparison between them. We have experimentally assessed both hybrid systems with respect to the standard HMM-based ASR system, for several noisy environments. On the one hand, the ANN/HMM system provides better results than the HMM-based system. On the other, the results achieved by the SVM/HMM system are slightly lower than those of the HMM system. Nevertheless, such a results are encouraging due to the current limitations of the SVM/HMM system