Context-dependent phoneme duration modeling with tree-based state tying

This letter presents two methods of modeling phoneme durations. One is the context-independent phoneme duration modeling in which duration parameters are stored in each phoneme. The other is the context-dependent duration modeling in which duration parameters are stored in each state shared by context-dependent phonemes. The phoneme duration model is compared with a without-duration model and a state duration model. Experiments are performed on a database collected over the telephone network. Experimental results show that duration information rejects out-of-task (OOT) words, well and that the context-dependent duration model yields the best performance among the tested models.