Continuously variable duration hidden Markov models for automatic speech recognition
Computer Speech and Language
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TSD'05 Proceedings of the 8th international conference on Text, Speech and Dialogue
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PRIB'12 Proceedings of the 7th IAPR international conference on Pattern Recognition in Bioinformatics
Hierarchical multi-channel hidden semi Markov graphical models for activity recognition
Computer Vision and Image Understanding
A voice command system for AUTONOMY using a novel speech alignment algorithm
International Journal of Speech Technology
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Hidden Markov modeling (HMM) techniques have been used successfully for connected speech recognition in the last several years. In the traditional HMM algorithms the probability of duration of a state decreases exponentially with time which is not appropriate for representing the temporal structure of speech. Non-parametric modeling of duration using semi-Markov chains does accomplish the task with a large increase in the computational complexity. Applying a post processing state duration penalty after Viterbi decoding adds very little computation but does not affect the forward recognition path. In this paper we present a way of modeling state durations in HMM using time dependent state transitions. This new inhomogeneous HMM (IHMM) does increase the computation by a small amount but reduces recognition error rates by 14-25%. Also, a suboptimal implementation of this scheme that requires no more computation than the traditional HMM is presented which also has reduced errors by 14-22% on a variety of databases.