NDLI: Novel Lookahead Decision Tree State Tying for Acoustic Modeling

Content Provider	IEEE Xplore Digital Library
Author	Jian Xue Yuxin Zhao
Copyright Year	2007
Description	Author affiliation: Dept. of Comput. Sci., Missouri Univ., Columbia, MO, USA (Jian Xue; Yuxin Zhao)
Abstract	This paper presents two new lookahead methods of constructing phonetic decision trees (PDTs) for acoustic model state tying, a constrained method and a stochastic method. The constrained lookahead method searches for optimal phonetic questions among pre-selected question sets, and reduces contributions of deeper decedents as a function of their levels in the tree. The stochastic full lookahead method uses subtree size instead of likelihood gain as a judgment in selecting a phonetic question for a node split, in order to find a compact tree that is consistent with training data. Since the computational cost of exhaustive lookahead is prohibitively high, a stochastic subtree generation method is used to explore most promising question at each node. We also propose using a phone-state dependent threshold instead of a fixed threshold of likelihood gain to decide if a node split should continue or not. Furthermore, we use a fast confusion network (CN) algorithm to combine recognition hypotheses produced by using acoustic models from different PDT training methods. Experimental results show that the proposed lookahead methods consistently decrease model size, and the integration of recognition hypotheses consistently improves recognition accuracy.
File Size	4967858
File Format	PDF
ISBN	1424407273
ISSN	15206149
DOI	10.1109/ICASSP.2007.367274
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2007-04-15
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Decision trees Stochastic processes Training data Context modeling Computer science Computational efficiency Vocabulary Speech recognition Merging Profitability phone-state dependent threshold phonetic decision trees constrained lookahead stochastic full lookahead
Content Type	Text
Resource Type	Article

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