The present invention comprises a system and method for speech verification using a confidence measure that includes a speech verifier which compares a differential score for a recognized word to a predetermined threshold value, where a recognized word is the word model that produced the highest recognition score. In one embodiment, a single threshold is used for each word in a vocabulary. In another embodiment, each word model has an associated threshold, so that a differential score for a recognized word is compared to a unique threshold associated with that word. In a further embodiment, pairs of confused words in the vocabulary are dealt with separately. If a confused word is the recognized word, the speech verifier compares the differential score to a threshold that depends on the word model that produced the next-highest recognition score. Different values for the various thresholds may maximize rejection accuracy or recognition accuracy. A trade-off between rejection accuracy and recognition accuracy may be made by utilizing an intermediate threshold value that is between a minimum threshold value and a maximum threshold value.
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to, and claims the benefit of, U.S. Provisional Application No. 60/160,859, entitled "System And Method For Speech Verification Using A Confidence Measure," filed Oct. 21, 1999, which is hereby incorporated by reference.
A method and detector for providing a noise resistant utterance detector is provided by extracting a noise estimate (15) to augment the signal-to-noise ratio of the speech signal, inverse filtering (17) of the speech signal to focus on the periodic excitation part of the signal and spectral reshaping (19) to accentuate separation between formants.
The present invention comprises a system and method for speech verification using an efficient confidence measure, and includes a speech verifier which compares a confidence measure for a recognized word to a predetermined threshold value in order to determine whether the recognized word is valid, where a recognized word corresponds to a word model that produces a highest recognition score. In accordance with the present invention, the foregoing confidence measure may be calculated using the recognition score for the recognized word and a pseudo filler score that may be based upon selected average recognition scores from an N-best list of recognition candidates.
