Using pitch frequency information in speech recognition

Automatic Speech Recognition systems typically use smoothed spectral features as acoustic observations. In recent studies, it has been shown that complementing these standard features with pitch frequency could improve the system performance of the system. While previously proposed systems have been studied in the framework of HMM/GMMs, in this paper we study and compare different ways to include pitch frequency in state-of-the-art hybrid HMM/ANN system. We have evaluated the proposed system on two different ASR tasks, namely, isolated word recognition and connected word recognition. Our results show that pitch frequency can indeed be used in ASR systems to improve the recognition performance.