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, comprising the steps of:

• (A) comparing a speech frame against each of the phone models of the existing active list to obtain a phone best score for each of the phone models of the existing active list;
• (B) determining a best phone best score among all the phone best scores of the phone models from the existing active list to obtain a global best score;
• (C) adding a first phone model of the phone models from the existing active list to the new active list of phone models if the phone best score of the first phone model is within a first predetermined value of the global best score;
• (D) adding a next phone model of the first phone model to the new active list if the phone best score of the first phone model is within a second predetermined value of a word ending score of the first phone model;
• (E) adding a next phone model of a next word of the first phone model to the new active list if the global best score is within a third predetermined value with respect to a word ending score of the first phone model.

A speech recognition apparatus comprising

• an audio transducer which receives a speech utterance;
• a processor coupled to said audio transducer to receive a speech frame of said speech utterance;
• a memory coupled to said processor, said memory storing a plurality of phone models in an existing active list of phone models, said processor pruning said existing active list to create a new active list of phone models, said processor
• comparing said speech frame 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, and
• adding a next phone model of a first phone model of the phone models of the existing active list to the new active list if the phone best score of the first phone model is within a first predetermined value of a phone ending score of the first phone model.

A speech recognition apparatus comprising

• an audio transducer which receives a speech utterance;
• a processor coupled to said audio transducer to receive a speech frame of said speech utterance;
• a memory coupled to said processor, said memory storing a plurality of phone models in an existing active list of phone models, said processor pruning said existing active list to create a new active list, said processor
• comparing said speech frame 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;
• determining a best phone best score among all the phone best scores of the phone models of the existing active list to obtain a global best score;
• and
• adding a next phone model of a next word of a first phone model of the phone models of the existing active list to the new active list if the global best score is within a first predetermined value with respect to a word ending score of the first phone model.