SPEECH RECOGNITION SYSTEM WITH MULTI-LEVEL PRUNING FOR ACOUSTIC MATCHING

A method of constructing a new active list of phone models from an existing active list of phone models during acoustic matching of a speech recognition system is described. A vector quantized speech vector is compared against each of the phone models in the existing active list to obtain a phone best score for each of the phone models of the existing active list. A best phone best score is determined among all the phone best scores of the phone models to obtain a global best score. A phone model of the phone models from the existing active list is added to the new active list of phone models if the phone best score of that phone model is within a first predetermined value of the global best score. A next phone model of the existing phone of the existing active list is added to the new active list if the phone ending score of that existing phone is within a second predetermined value of a best score of the existing phone model. A next (e.g. first) phone model of a next word of a particular phone model of the existing active list is added to the new active list if the ending score of that particular phone model is within a third predetermined value of the global best score.