Speech processing apparatus and method
First Claim
1. An apparatus for measuring the likelihood that a series of signals corresponding to a first hidden Markov model will be identified with a second hidden Markov model using a data store configured to store a plurality of hidden Markov models, said models each comprising data identifying a series of probability density functions for a number of states, said apparatus comprising:
- a calculator operable to calculate for each of the probability density functions of a first stored model stored in said data store values indicative of the logarithmic probability of a signal corresponding to a state identified by said stored probability density function would be identified with the states identified by probability density functions of a second stored model stored in said data store;
a determinator operable to determine from values calculated by said calculator, a set of transitions between said states of said first and second models stored in said data store where the states are associated with values indicative of the highest probabilities of signals corresponding to states of said first stored model being identified with states of said second stored model; and
an output unit operable to output as a measure of the likelihood of a series of signals corresponding to said first stored model being identified with said second stored model, the sum of calculated values for said set of transitions divided by the number of steps in said set of transitions.
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Abstract
A speech recognition system is disclosed including a model generation unit (20) and a speech recognition unit (22). When signals are received from a microphone (7) the model generation unit (20) utilises the signals to generate hidden Markov models that are stored in a hidden Markov model database (24). Subsequently, when utterances are to be recognised, the speech recognition unit (22) utilises the stored hidden Markov models to associate an utterance with a word. When a new hidden Markov model is generated by the model generation unit (20) the new hidden Markov model is processed by a confusability checker (26) against the hidden Markov models already stored in the database (24). A value indicative of the likelihood of utterances corresponding to the new model being confused with previously stored models is determined by the confusability checker (26) directly from the parameters for the new hidden Markov model and the other hidden Markov models stored in the database (24). If this value indicates a high likelihood of words being confused, the new entry is deleted from the database (24) and a warning is output to the user.
7 Citations
20 Claims
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1. An apparatus for measuring the likelihood that a series of signals corresponding to a first hidden Markov model will be identified with a second hidden Markov model using a data store configured to store a plurality of hidden Markov models, said models each comprising data identifying a series of probability density functions for a number of states, said apparatus comprising:
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a calculator operable to calculate for each of the probability density functions of a first stored model stored in said data store values indicative of the logarithmic probability of a signal corresponding to a state identified by said stored probability density function would be identified with the states identified by probability density functions of a second stored model stored in said data store;
a determinator operable to determine from values calculated by said calculator, a set of transitions between said states of said first and second models stored in said data store where the states are associated with values indicative of the highest probabilities of signals corresponding to states of said first stored model being identified with states of said second stored model; and
an output unit operable to output as a measure of the likelihood of a series of signals corresponding to said first stored model being identified with said second stored model, the sum of calculated values for said set of transitions divided by the number of steps in said set of transitions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of obtaining a measure of the likelihood that a series of signals corresponding to a first hidden Markov model will be identified with a second hidden Markov model, said models each comprising data identifying a series of probability density functions for a number of states, said method comprising:
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calculating for each of said probability density functions of said first model values indicative of the logarithmic probability of a signal corresponding to a state identified by said probability density function would be identified with the states identified by said probability density functions of said second model;
determining from said calculated values a set of transitions between said states of said models where said states are associated with values indicative of the highest probabilities of signals corresponding to states of said first model being identified with states in said second model; and
outputting as a measure of the likelihood of a series of signals corresponding to said first hidden Markov model being identified with said second hidden Markov model, the sum of calculated values for said set of transitions divided by the number of steps in said set of transitions. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification