7th International Conference on Spoken Language Processing

September 16-20, 2002
Denver, Colorado, USA

Mutual Information Phone Clustering for Decision Tree Induction

Ciprian Chelba (1), Rachel Morton (2)

(1) Microsoft Research, USA; (2) Microsoft Corporation, USA

The paper presents an automatic method for devising the question sets used for the induction of classification and regression trees. The algorithm employed is the well-known mutual information based bottom-up clustering applied to phone bigram statistics. The sets of phones at the nodes in the resulting binary tree are used as question sets for clustering context-sensitive (tri-phone) HMM output distributions in a large vocabulary speech recognizer. The algorithm is shown to perform as well and sometimes significantly better than question sets devised by human experts for a Spanish and German system evaluated on several tasks, respectively. It eliminates the need for linguistic expertise and it provides a faster solution as well.


Full Paper

Bibliographic reference.  Chelba, Ciprian / Morton, Rachel (2002): "Mutual information phone clustering for decision tree induction", In ICSLP-2002, 1005-1008.