Patent ID: 7389229

Claim:
A speech recognition system comprising: a clustering tree configured to classify a series of sounds into predefined clusters based on one of the sounds and on a predetermined number of neighboring sounds that surround the one of the sounds, where the clustering tree comprises: a first level with a first hierarchical arrangement of decision nodes in which the decision nodes of the first hierarchical arrangement are associated with a first group of questions relating to the series of sounds, a second level with a second hierarchical arrangement of decision nodes in which the decision nodes of the second hierarchical arrangement are associated with a second group of questions relating to the series of sounds, the second group of questions discriminating at a finer level of granularity within the series of sounds than the first group of questions, and a third level with a third hierarchical arrangement of decision nodes in which the decision nodes of the third hierarchical arrangement are associated with a third group of questions discriminating at a finer level of granularity within the series of sounds than the second group of questions; and a plurality of speech recognition models trained to recognize speech based on the predefined clusters, the plurality of speech recognition models comprising: a first model associated with the first level and including a triphone non-crossword speech recognition model, a second model associated with the second level and including a quinphone non-crossword speech recognition model, and a third model associated with the third level and including a quinphone crossword speech recognition model.