JP2014074732A - Voice recognition device, error correction model learning method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To learn an error correction model used when recognizing voice while suppressing learning cost.SOLUTION: A voice language resource storage unit 21 stores voice data of speech of a specified speaker and text data which is a correct sentence of the speech, and a statistic model storage unit 31 stores an acoustic model of a specified speaker and a language model by the subject. A recognition error generation unit 4 voice-recognizes the voice data stored in the voice language resource storage unit 21 by using the acoustic model of the specified speaker and the language model of the specified topic stored in the statistic model storage unit 31, and generates a voice recognition result including a recognition error. An error correction model learning unit 5 analyzes a tendency of the recognition error statistically from the voice recognition result including the recognition error and the correct sentence shown by the text data, and generates an error correction model. A model integration unit 6 generates an integrated model in which the error correction model generated by the error correction model learning unit 5 and a plurality of language models stored in the statistic model storage unit 31 are integrated.

Description

  The present invention relates to a speech recognition device, an error correction model learning method, and a program.

  For error correction in speech recognition, statistical error correction models obtained as a result of learning by statistically learning the tendency of speech recognition errors using linguistic features from speech and transcriptions (correct sentences) There is a technology for improving the performance of speech recognition by using (see, for example, Non-Patent Document 1).

Kobayashi et al., “News speech recognition by discriminative scoring based on word error minimization”, IEICE Journal, vol.J93-D no.5, 2010, p. 598-609

  In speech recognition, a word is predicted using a statistical language model, and in order to improve the word prediction performance, a plurality of statistical language models are often used in an integrated manner. In learning of an error correction model by the technique of Non-Patent Document 1, speech recognition results including recognition errors are used as learning data in order to learn an error tendency of speech recognition, and this learning data is statistically integrated according to different criteria. Generated by speech recognition using a language model. Therefore, when the integration method is changed, it is necessary to recreate a speech recognition result as learning data. Such an error correction model learning method is expensive to generate a speech recognition result and to learn the error correction model. Therefore, it cannot be said that it is an efficient learning method when error correction models are generated for various topics and speakers and speech is recognized.

  The present invention has been made in view of such circumstances, and provides a speech recognition apparatus, an error correction model learning method, and a program capable of learning an error correction model used for speech recognition while reducing costs. .

[1] According to one aspect of the present invention, a spoken language resource storage unit that stores speech data of an utterance of a specific speaker and text data that is a correct sentence corresponding to the speech data, an acoustic model of the specific speaker, and The speech model is speech-recognized using a statistical model storage unit that stores topical language models, the acoustic model of the specific speaker and the language model of the specific topic, and a speech recognition result including a recognition error is obtained. A recognition error generation unit that statistically analyzes the tendency of recognition errors from the recognition error generation unit to be generated, the speech recognition result generated by the recognition error generation unit, and the correct sentence indicated by the text data; An error correction model learning unit that generates an error correction model that corrects a tendency of the above, a sound model of the specific speaker, and a plurality of the language models before being used to generate the error correction model The error correction model learning is performed based on a recognition error obtained by speech recognition of speech data different from the speech data, and comparing a correct sentence candidate obtained by speech recognition with a correct sentence corresponding to the different speech data. Statistically calculating a mixture weight when integrating the plurality of language models into the error correction model generated by the unit, and correcting the error correction of the language model of a topic different from the specific topic according to the calculated mixture weight And a model integration unit that generates an integrated model by integrating with a model.
According to this invention, the speech recognition apparatus recognizes speech data of a specific speaker using the acoustic model of the specific speaker and a language model of the specific topic, and learns speech recognition results including recognition errors as learning data. Generate as The speech recognizer generates an error correction model by statistically analyzing the tendency of recognition errors from the learning data generated from the speech data and the correct sentence of the speech data, and then generates the error correction model and other than the specific topic Are integrated with the language model to generate an integrated model used for speech recognition of a specific speaker and a specific topic.
Thereby, it is not necessary to recreate a speech recognition result as learning data according to the language model integration method, and the integrated model can be efficiently learned.

[2] One aspect of the present invention is the speech recognition apparatus described above, wherein the model integration unit includes the recognition error obtained from the correct sentence candidate and the correct sentence candidate obtained from the error correction model. An evaluation function calculated using an evaluation function determined using the acoustic score and the language score in which the recognition error tendency is corrected, and the language score of the correct sentence candidate obtained from the language model of a topic different from the specific topic The mixing weight is statistically calculated based on the value.
According to this invention, the speech recognition apparatus recognizes the recognition error of the word included in the correct sentence candidate when the text data corresponding to the speech data is regarded as the correct sentence, and the sound of the correct sentence candidate obtained by the error correction model. The evaluation value calculated by the evaluation function determined based on the language score with the corrected score and recognition error tendency and the language score of the correct sentence candidate obtained from the language model of the topic different from the specific topic is the most recognized error The blending weight of the language model is calculated so that the evaluation value indicates that there is little, and the error correction model and the plurality of language models are integrated by the calculated blending weight.
As a result, the speech recognition device generates an error correction model suitable for speech recognition of the speech about a specific topic of a specific speaker, and then integrates the language models of other topics so that the recognition rate increases. Mixing weights can be determined.

[3] One aspect of the present invention is the speech recognition device described above, in which the recognition error generation unit uses the acoustic model of the specific speaker to determine the utterance content of the text data corresponding to the specific topic. Speech synthesis is performed to generate speech data, and the generated speech data is speech-recognized using the acoustic model of the specific speaker and the language model of the specific topic to generate a speech recognition result including a recognition error. It is characterized by that.
According to the present invention, the speech recognition apparatus generates speech data of a specific speaker by speech synthesis from text data of a specific topic, and an error correction model from the speech recognition result of the generated speech data and a correct sentence indicated by the text data. Is generated.
Thereby, the speech recognition apparatus can generate an error correction model from text data of a specific topic even when the speech data of the specific speaker is not statistically sufficient.

[4] One aspect of the present invention is the speech recognition apparatus described above, wherein the error correction model includes continuous words, phonemes constituting the words, a plurality of discontinuous words, a co-occurrence relationship between phonemes, It is defined using a feature function representing a linguistic feature based on syntactic information or semantic information of a word and its feature weight, and the error correction model learning unit is configured to obtain the feature obtained from the speech recognition result. The feature weight is statistically calculated based on an evaluation value calculated by an evaluation function determined using a function value and the recognition error included in the speech recognition result, and the error is calculated using the calculated feature weight. A modified model is generated.
According to the present invention, the speech recognition apparatus uses the feature weight obtained from the speech recognition result to use the feature weight used by the error correction model defined by the feature function representing the linguistic feature based on the word, phoneme, and the like and the feature weight. An error correction model is generated by determining an evaluation value calculated by an evaluation function determined using a function value and a recognition error to be an evaluation value indicating that the recognition error is the smallest.
As a result, the speech recognition apparatus can generate error correction models suitable for speech recognition of utterances on specific topics of specific speakers, and then integrate error tendencies on other topics.

[5] One aspect of the present invention is the speech recognition device described above, which recognizes speech data of speech of the specific topic by the specific speaker using the integrated model generated by the model integration unit. A voice recognition unit is further provided.
According to this invention, the speech recognition apparatus performs speech recognition based on the integrated model learned about the specific speaker and the specific topic.
Thereby, the speech recognition apparatus can obtain a speech recognition result with a good recognition rate for the utterance of the specific topic of the specific speaker.

[6] According to one aspect of the present invention, a spoken language resource storage process of storing speech data of a specific speaker's utterance and text data that is a correct sentence corresponding to the speech data, an acoustic model of the specific speaker, and The speech data is speech-recognized using a statistical model storing process for storing topic-specific language models, the acoustic model of the specific speaker and the language model of the specific topic, and a speech recognition result including a recognition error is obtained. The recognition error is statistically analyzed from the recognition error generation process to be generated, the speech recognition result generated in the recognition error generation process, and the correct sentence indicated by the text data. An error correction model learning process for generating an error correction model that corrects the tendency of the error, and the generation of the error correction model using the acoustic model of the specific speaker and the plurality of language models. Based on a recognition error obtained by speech recognition of speech data different from the speech data used in the above, and comparing a correct sentence candidate obtained by speech recognition with a correct sentence corresponding to the different speech data, the error A statistical weight is calculated when the plurality of language models are integrated into the error correction model generated in the correction model learning process, and the language model of a topic different from the specific topic is calculated according to the calculated mixing weight. And a model integration process of generating an integrated model by integrating with the error correction model.

[7] According to one aspect of the present invention, a computer stores speech language resource storage means for storing speech data of a specific speaker's utterance and text data that is a correct sentence corresponding to the speech data; A speech model including a recognition error by recognizing the speech data using a statistical model storage unit that stores an acoustic model and a topical language model; and the acoustic model of the specific speaker and the language model of the specific topic. The recognition error generation means for generating a recognition result, the speech recognition result generated by the recognition error generation means, and the tendency of the recognition error are statistically analyzed from the correct sentence indicated by the text data. The error correction model learning means for generating an error correction model for correcting the tendency of recognition errors, the acoustic model of the specific speaker, and a plurality of the language models Based on a recognition error obtained by recognizing speech data different from the speech data used for generating the correct model and comparing a correct sentence candidate obtained by speech recognition with a correct sentence corresponding to the different speech data Statistically calculating a mixing weight when integrating the plurality of language models into the error correction model generated by the error correction model learning means, and according to the calculated mixing weight, a topic different from the specific topic is calculated. It is a program for functioning as a speech recognition device comprising model integration means for generating an integrated model by integrating the language model with the error correction model.

  ADVANTAGE OF THE INVENTION According to this invention, the error correction model used when recognizing a speech can be learned, suppressing learning cost. Therefore, it is possible to efficiently learn error correction models for various topics and speakers.

It is a figure which shows the procedure of the integrated model learning in the speech recognition apparatus by one Embodiment of this invention. It is a figure which shows the outline | summary processing flow of the integrated model learning process of the speech recognition apparatus by the embodiment. It is a functional block diagram which shows the structure of the speech recognition apparatus by the embodiment. It is a figure which shows the processing flow of the production | generation process of the pseudo speech recognition result by the embodiment. It is a figure which shows the processing flow of the error correction model learning process by the embodiment. It is a figure which shows the processing flow of the model integration process by the embodiment. It is a figure which shows the procedure of the error correction model learning by the conventional method.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[1. Overview of this embodiment]
In a so-called error correction model that reflects the error tendency of speech recognition, a statistical acoustic model (hereinafter referred to as “acoustic model”) and a statistical language are used in addition to speech and text data to learn the error tendency. A model (hereinafter referred to as “language model”) is required. A conventional speech recognition apparatus recognizes speech data using these two statistical models, and generates a hypothesis (speech recognition result) including a recognition error. In many cases, the language model used when generating a hypothesis is not only a language model learned from a single text set, but also a combination of language models individually learned from a plurality of different text sets. In the conventional method, language models are integrated first, and then an error correction model consistent with the integrated language model is learned. However, in this learning order, each time a language model is integrated with a different combination, a hypothesis including a recognition error used for learning of an error correction model is generated, which is not efficient from a practical standpoint.

  Therefore, the speech recognition apparatus according to the present embodiment changes the order of language model integration and error correction model learning from the conventional order, and uses only a specific language model and acoustic model first to detect the error tendency of speech recognition. A reflected hypothesis is generated, and an error correction model is learned from the generated hypothesis. Thereafter, the speech recognition apparatus according to the present embodiment integrates the learned error correction model and a plurality of language models learned from other text data. As described above, the speech recognition apparatus according to the present embodiment efficiently learns an error correction model by separately performing learning of an error correction model and integration using language models having different learning conditions. The speech recognition apparatus according to the present embodiment improves the recognition performance of various speakers and topics by using the error correction model generated efficiently as described above.

[2. Outline of processing of voice recognition device]
Next, the processing outline of the speech recognition apparatus according to the embodiment of the present invention will be described.
As described above, the speech recognition apparatus according to the present embodiment learns an error correction model using a specific acoustic model and language model, and then integrates the learned error correction model and a plurality of language models that perform word prediction. Hereinafter, an error correction model integrated with a plurality of language models is referred to as an integrated model. The speech recognition apparatus of this embodiment obtains an integrated model that matches the topic and speaker of the speech recognition target by adjusting the mixing weight between the language models when integrating.

[2.1 Error correction model of conventional method]
According to Bayes' theorem, when speech input x is given, a word string w ^ (“^” represents “hat”) that is likely to be associated with speech input x is expressed by the following equation (1). It can ask for.

The voice input x and the word string w correspond to, for example, a unit of speech, and P (w | x) is a posterior probability that the word string w that is a sentence hypothesis is obtained when the voice input x occurs.
P (x | w) is a likelihood indicating acoustic likelihood for the word string w, and the score (acoustic score) is a hidden Markov model (HMM) and a Gaussian mixture distribution (Gaussian Mixture). Calculation based on an acoustic model represented by Model, GMM). In other words, when an acoustic feature amount is given, a score representing the likelihood of each of a plurality of correct candidate word strings is an acoustic score.
On the other hand, P (w) is a linguistic likelihood for the word string w, and the score (language score) is calculated by a language model such as a word n-gram model. In other words, when a word string before or after a speech recognition target word, or both word strings before and after the given word string, a score representing the likelihood of each of a plurality of correct answer word strings is a language score. The word n-gram model gives the occurrence probability of the next word from the history of the word (N-1) based on the statistics of N word chains (N is 1, 2, or 3, for example). It is a model.

  In the following description, HMM-GMM is used for the acoustic model and n-gram is used for the language model.

  When P (x | w) P (w) in Equation (1) is maximum, the logarithm is also maximum. Therefore, in speech recognition, the evaluation function g (w | x) is determined as in the following equation (2) based on the Bayes' theorem in the above equation (1). Note that κ is a weight of the language score P (w) with respect to the acoustic score P (x | w).

  Then, as shown in the following equation (3), the result of the evaluation function g (w | x) indicated by the equation (2) is the maximum from the set L of correct candidate word strings w for the voice input x. The word string w ^ is selected as the voice recognition result of the voice input x.

  In the error correction model in the conventional method, equation (1) is changed to the following equation (4).

In formula (4), expΣ _i λ _i f _i (w) is a penalty score reflecting the error tendency of the word string w, f _i (w) is the i-th feature function, and λ _i is the feature function f _i ( The feature weight of w). The feature function is defined as a function that becomes the number if a linguistic rule is established in a given word string (here, word string w), and is 0 if not established. Specific examples of linguistic rules include the following.

(A) Number of consecutive word binary groups (u, v) included in word string w (b) Number of non-contiguous word binary groups (u, v) included in word string w

As shown in the above equation (4), the error tendency of speech recognition is expressed as a penalty for a linguistic feature by a feature function and a feature weight, and is estimated based on an evaluation function that minimizes a word error in learning data. The That is, the learning of error tendency in the conventional method is to obtain the feature weight λ _i of the equation (4) using the speech recognition result of speech data and the correct answer sentence as learning data.

[2.2 Techniques Applied to the Speech Recognition Apparatus According to the Present Embodiment]
As described in the previous section, the speech recognition apparatus according to the present embodiment generates a statistical error correction model by learning an error tendency of speech recognition depending on a specific speaker and topic. The speech recognition apparatus according to this embodiment applies the generated error correction model to speech recognition to improve the recognition rate.

  In order to learn the error correction model by statistical means, learning data is required. The learning data is a word string including an error, and a speech recognition result is generally used. Therefore, what kind of word string is included in the learning data depends on the acoustic model and language model used for speech recognition.

  On the other hand, in speech recognition, a plurality of language models are often used in an integrated manner to improve word prediction accuracy. Generally, language models are integrated by linear interpolation as shown in the following equation (5).

P _j is a language score when the j-th language model is used. Θ _j is a coefficient called a blending weight for the j-th language model and satisfies Σ _j θ _j = 1. Hereinafter, θ _j is also referred to as a model parameter. Normally, learning data used for model learning such as a language model is different from learning data used for model parameter learning, and the learning data used for model parameter learning is generally called development data.

  In the conventional method, speech recognition is performed using a model in which a plurality of language models are integrated by a method such as linear interpolation as shown in Expression (5), and a speech recognition result as learning data is obtained. Then, an error correction model is learned using the obtained speech recognition result.

FIG. 7 is a diagram showing a procedure for error correction model learning according to the conventional method.
As shown in the figure, in the conventional method, an acoustic model (acoustic model A _{2 in} the figure) of a specific speaker is selected from acoustic models A _{1 to} A _N as acoustic models used for error learning, and a language model is selected. A plurality of language models B _{1 to} B _M are integrated. The learning data of the error correction model is obtained by voice recognition of the voice data using the acoustic model of the specific speaker and the integrated language model. Therefore, in the conventional method, when the combination condition of a plurality of language models changes (that is, when the value of the model parameter θ _j in Expression (6) changes), the speech recognition result that is the learning data of the error correction model is changed. It will change a lot. Therefore, in order to learn an error correction model suitable for a certain condition, a speech recognition result must be generated according to the combination of language models. This takes too much calculation time to generate learning data, and is not efficient.

FIG. 1 is a diagram showing an integrated model learning procedure in the speech recognition apparatus according to the present embodiment. As shown in the figure, the speech recognition device according to the present embodiment, (in the figure, an acoustic model A ₂₎ acoustic models of a particular speaker selected from among acoustic models A ₁ to A _N and language model B ₁ (in the figure, the language model B ₁₎ language model of a specific topic selected from among .about.B _M generates an error correction model as learning data the voice recognition results using a problem of the conventional method language model The integration of the language models (B _{2 to} B _{M in} the figure) is changed after the error correction model is generated. With this method, the error tendency for the integrated language model can only be estimated approximately. However, if an error correction model depending on a specific topic is to be learned, under the assumption that at most one language model reflecting topic dependency can be learned, error tendency learning can be performed with a good approximation. Conceivable.

  Therefore, when the speech recognition apparatus of the present embodiment learns an error tendency about a specific topic and a speaker with respect to evaluation data to be subjected to speech recognition, one language model related to the topic of interest is prepared, Used for speech recognition along with an acoustic model of a specific speaker. The evaluation data is unknown speech data different from speech data used when learning a language model or an acoustic model. Thereby, the speech recognition apparatus of the present embodiment can generate learning data including an error reflecting a specific speaker and topic.

  For example, suppose that an error correction model specialized for cooking topics (and a specific speaker) is to be created. In this case, a language model learned from a topic that is not directly related to cooking is often integrated with a language model related to the topic of cooking by linear interpolation. This is because a language model specialized for a specific topic usually has less learning data, and the accuracy (estimation accuracy) of predicting a word by speech recognition deteriorates, and the statistical robustness of the language model is lost. Because. Therefore, in order to ensure this robustness, integration with other language models is performed. However, it is sufficient to use a language model specialized in the topic of cooking if you want to capture the error tendency of cooking.

  The speech recognition apparatus of the present embodiment generates learning data by combining a specific acoustic model and a specific language model, learns an error correction model, and mixes other language models according to the target task. . This eliminates the need for a procedure for generating learning data each time the language model combination condition is changed, thereby greatly reducing costs such as calculation time.

[2.3 Overview of integrated model learning process]
FIG. 2 shows an outline processing flow of the integrated model learning process by the speech recognition apparatus of the present embodiment.
The speech recognition apparatus according to the present embodiment stores in advance a speech language resource data composed of speech data and text data as a transcription thereof in a speech language resource storage unit. Furthermore, the speech recognition apparatus of the present embodiment stores the acoustic model and the language model in advance in the statistical model storage unit. Label data indicating at least a speaker is assigned to the voice data and the acoustic model, and label data indicating at least a topic or a program is assigned to the text data and the language model.

(Step S1): A topic and a speaker related to a task whose recognition performance is to be improved are specified.
First, the user of the speech recognition apparatus of this embodiment selects a topic and a speaker whose recognition rate is to be improved. For example, the user can select a speaker name or topic (cooking / health / travel etc.) based on the program, topic, or speaker information indicated by the label data attached to each speech data or text data of the spoken language resource data. ) Label data is specified. The speech recognition apparatus according to the present embodiment selects speech data or text data to which a designated speaker name or topic label data is assigned as speech language resource data used for learning an error correction model.

(Step S2): A language model / acoustic model used in a task whose recognition performance is to be improved is selected.
Next, the speech recognition apparatus according to the present embodiment selects a language model and an acoustic model suitable for the topic or speaker specified in step S1 from the statistical model storage unit. These models may be acoustic models and language models estimated by statistical means from speech data and text data stored in the spoken language resource storage unit, and acoustic models and language models estimated from other speech data and text data. It may be a language model.

(Step S3): A hypothesis including a recognition error of speech recognition is generated from the selected acoustic model and language model and the speech language resource data.
The speech recognition apparatus according to the present embodiment recognizes speech data selected in step S1 using the acoustic model and language model selected in step S2, and generates a hypothesis (speech recognition result) including a recognition error as learning data. When text data is selected in step S1, the speech recognition apparatus according to the present embodiment can generate a hypothesis including a pseudo error using an acoustic model and a language model.

(Step S4): An error correction model is learned using the generated hypothesis.
The speech recognition apparatus of this embodiment uses the hypothesis including the recognition error obtained in step S3 as learning data, and estimates an error correction model by statistical means. When estimating the error correction model, the speech recognition apparatus according to the present embodiment obtains the linguistic features used for the correction model estimation in step S3 and the transcription (correct sentence) indicated by the text data selected in step S1. And a hypothesis including a given error.

(Step S5): The error correction model and an arbitrary number of language models are integrated.
The speech recognition apparatus according to the present embodiment integrates the error correction model obtained in step S4 and an arbitrary number of language models stored in the statistical model storage unit by a technique such as linear interpolation, and generates an integrated model. . At this time, the speech recognition apparatus of the present embodiment uses topic / speaker speech data whose recognition performance is to be improved, and estimates and integrates mixed weights (model parameters) of each language model so as to maximize the recognition performance. To do.

  (Step S6): The speech recognition apparatus of the present embodiment recognizes speech of a specific speaker's specific topic using the integrated model generated in Step S5.

[3. Configuration of voice recognition device]
FIG. 3 is a functional block diagram showing the configuration of the speech recognition apparatus 1 according to one embodiment of the present invention, and only the functional blocks related to the present embodiment are extracted and shown.
The speech recognition device 1 is realized by a computer device, and as shown in the figure, a speech language resource management unit 2, a statistical model management unit 3, a recognition error generation unit 4, an error correction model learning unit 5, a model integration unit 6, A voice recognition unit 7 and a storage unit 8 are provided.

  The spoken language resource management unit 2 includes a spoken language resource storage unit 21 that stores spoken language resource data including speech data and text data. The spoken language resource management unit 2 collects broadcast audio / caption data D1 acquired from the outside as the spoken language resource data, and writes it into the spoken language resource storage unit 21. At this time, the spoken language resource management unit 2 assigns label data indicating the name of the speaker (speaker name) if it is audio data, depending on the contents of the broadcast audio / subtitle data D1, and if it is text data. Label data indicating contents such as a topic is attached and stored in the spoken language resource storage unit 21. Note that the topic may be included in the label data of the voice data, and the speaker name may be included in the label data of the text data. The voice data indicates a feature amount obtained by performing a short-time spectrum analysis on the voice waveform of the utterance, and the text data indicates a transcription (correct sentence) of the utterance content. One text data can include a plurality of sentences.

  The user selects a speaker and a topic for which a desired integrated model is to be generated, according to the speech data stored in the speech language resource storage unit 21 and the label data attached to the text data. The speaker and the topic are specified by this selection work, and the spoken language resource management unit 2 specifies the spoken language resource data of the label data corresponding to the specified speaker and the topic. The spoken language resource management unit 2 generates speech / text data D4 for generating learning data used for learning of the error correction model from the identified spoken language resource data, and development data D5 for estimating model parameters of the integrated model. Are selected so as not to overlap with each other, and are written in the storage unit 8. The spoken language resource management unit 2 outputs specific speaker data D2 indicating the specified speaker and specific topic data D3 indicating the specified topic to the statistical model management unit 3.

  The statistical model management unit 3 includes a statistical model storage unit 31 that stores an acoustic model and a language model to which label data is assigned. The label data of the acoustic model indicates the name of the speaker, and the label data of the language model indicates the topic name. The statistical model management unit 3 includes an acoustic model and a language stored in the statistical model storage unit 31 by label data of a speaker or a topic indicated by the specific speaker data D2 and the specific topic data D3, or a topic similar to the topic. An acoustic model D6 and a language model D7 are selected from the models. Furthermore, the statistical model management unit 3 selects one or more language models D8 different from the language model D7 from the language models stored in the statistical model storage unit 31.

  The recognition error generation unit 4 recognizes speech data included in the speech / text data D4 using the acoustic model D6 and the language model D7, and generates and stores learning data D9 that is a speech recognition result including a recognition error. Write to part 8. The recognition error generation unit 4 generates learning data D9 by using a pseudo hypothesis generation method that does not use voice recognition for text data that does not have corresponding voice data among the voice / text data D4.

  The error correction model learning unit 5 learns the error tendency of the speech recognition by statistical means using the speech recognition result indicated by the learning data D9 and the correct sentence indicated by the text data in the speech / text data D4, and corrects the error. A model D10 is generated. The error correction model learning unit 5 writes the generated error correction model D10 in the storage unit 8.

  The model integration unit 6 integrates the error correction model D10 and an arbitrary number of language models D8 other than the specific topic to generate an integration model D11 and writes it in the storage unit 8.

The speech recognition unit 7 performs speech recognition using the conventional language model and acoustic model stored in the statistical model storage unit 31 and the integrated model indicated by the integrated model D11, and includes speech recognition result data indicating a speech recognition result. D12 is output.
The storage unit 8 stores various data used by each functional unit.

[4. Detailed processing procedure in voice recognition apparatus]
Next, a detailed processing procedure executed by the speech recognition apparatus 1 in the integrated model learning process shown in FIG. 2 will be described.

[4.1 Step S1]
The spoken language resource management unit 2 collects the broadcast voice / caption data D1 as the voice data and text data of the voice language resource data and stores them in the voice language resource storage unit 21. Alternatively, the spoken language resource management unit 2 collects web data from a server computer or the like connected to the speech recognition apparatus 1 via a network, and stores it in the spoken language resource storage unit 21 as spoken language resource data consisting only of text data. Label data is assigned to the collected speech data and text data by the speech language resource management unit 2 or manually. For example, the program information given to the broadcast audio / caption data D1 can be used for the label data. When the web data is, for example, news text data, the category to which the news belongs can be acquired from the web data and used as label data.

  In order to generate learning data used for learning an error correction model, a user designates a speaker and a topic by referring to a set of label data stored in the spoken language resource storage unit 21, and a keyboard or the like is not shown. The specific speaker data D2 and the specific topic data D3 are input by the input means. The spoken language resource management unit 2 identifies the combination of the speech data and the text data corresponding to the specific speaker data D2 and the specific topic data D3 based on the label data stored in the spoken language resource storage unit 21. A part of the set is selected as voice / text data D4. Further, the spoken language resource management unit 2 identifies a combination of the speech data and the text data corresponding to the specific speaker data D2 and the specific topic data D3 by the same procedure, and selects some combinations from the specified language model. Is selected as development data D5 for estimating the model parameters. At this time, the spoken language resource management unit 2 selects the development data D5 so as not to overlap with the speech / text data D4. The spoken language resource management unit 2 may specify text data corresponding to the specific topic data D3 and select the speech / text data D4 from the specified text data. The selection method of the voice / text data D4 and the development data D5 is arbitrary, but the amount of the development data D5 may be about several percent of the amount of the voice / text data D4.

[4.2 Step S2]
In the statistical model storage unit 31, speech data and text data stored in the speech language resource storage unit 21 as speech language resource data, or an acoustic model and language model learned from other speech language resource data are stored in the label data. Are stored in association with each other. The statistical model management unit 3 selects an acoustic model corresponding to the specific speaker data D2 and a language model corresponding to the specific topic data D3 based on the label data stored in the statistical model storage unit 31. Further, the statistical model management unit 3 selects one or more language models different from the language model D7 from the language models stored in the statistical model storage unit 31 as the language model D8 to be integrated with the error correction model. .

[4.3 Step S3]
The recognition error generation unit 4 recognizes speech data included in the speech / text data D4 using the acoustic model D6 and the language model D7. Here, the speech recognition result is the top n (n is an integer of 1 or more) maximum likelihood word series (n-best) or word lattice. The recognition error generation unit 4 writes learning data D9 indicating the voice recognition result of the voice data in the storage unit 8.

  Note that the recognition error generation unit 4 cannot use speech recognition when the speech / text data D4 is text data that is not associated with speech data, so that pseudo speech recognition is performed as shown in FIG. Generate results.

  FIG. 4 is a diagram illustrating a processing flow of a pseudo speech recognition result generation process by the recognition error generation unit 4. This generation process is the same as the procedure used in speech synthesis described in the document “Tokuda, Application of Hidden Markov Model to Speech Synthesis, IEICE Technical Report SP-99, 1999, p. 47-54, 1999”. Based.

(Step S30: pronunciation sequence generation process)
First, the recognition error generation unit 4 converts each word string indicated by the text data included in the speech / text data D4 into a correct phoneme string. Various conversion methods are conceivable for the conversion process of the correct phoneme string, but in the present embodiment, conversion is performed as follows.

  If the word string is w and the phoneme string is q, the correct phoneme string q ^ to be obtained is obtained by the following equation (6).

  Here, the conditional probability P (q | w) of the phoneme sequence q when the word sequence w is given is obtained by the following equation (7).

  However, S (w, q) is a score based on a logarithmic linear model, and is obtained by the following equation (8).

In Equation (8), f _i (w, q) is the i-th feature function, and λ _i is the feature weight of the feature function f _i (w, q).
Examples of the feature function used in Equation (8) include the following.

(A) The pronunciation of the _i -th word w _i = u in the word string w is 1 if q _i = α, and 0 otherwise. For example, if the word w _i is the word u “go” and the pronunciation q _i of the word w _i matches the phoneme sequence α “/ i // Q // t // e /”, the word w _i is “1”.
(B) i-1th word w _i-1 = word u of word string w, i-th word w _i = word v and pronunciation q _i = β is 1, otherwise 0. For example, the word w _i-1 is the word u "to", immediately after the word w _i is the word u "Go", and the pronunciation q _i of word w _i is the phoneme string α "/ i / / Q / / If it matches “t // e /”, it becomes “1”.

  A plurality of phoneme strings q can be generated for the word string w. Therefore, in the above, the correct pronunciation (phoneme string) is estimated using the word notation information, and the feature function of a value other than 0 increases as it appears more easily, and the score of equation (8) increases. Become.

The storage unit 8 stores in advance a pronunciation dictionary which is a table in which a word notation and a phoneme string indicating the pronunciation of the word are associated as the word / pronunciation conversion model D31. One or more phoneme strings can correspond to one word notation. Recognition error generation unit 4, the word sequence represented by the text data of the speech text data D4 and w, each word w ₁ constituting the word string _w, w 2, _... words-phonetic conversion model D31 each phoneme string Get from. The recognition error generator 4 combines the phoneme strings acquired for the words in the order of the words w ₁ , w ₂ ,... Constituting the word string w to generate a phoneme string q of the word string w. Thus, the word _w 1 word sequence w is, _{w 2,} consists ..., phoneme string corresponding to a word _{w i} is _{n i} number (i = 1, ...) when there is a phoneme sequence q is generated as Paienu _i . The recognition error generation unit 4 calculates the conditional probability P (q | w) of each phoneme string q generated by the expressions (7) and (8) for the word string w, and calculates the calculated conditional probability P (q | W) is used to obtain a correct phoneme string q ^ which is a probable pronunciation sequence when the word string w is given by Equation (6). The model parameter Λ = (λ ₁ , λ ₂ ,...) Used in Equation (8) uses a value learned in advance from learning data consisting of a separately prepared word string and correct pronunciation sequence.

(Step S31: HMM state sequence generation process)
The recognition error generator 4 obtains the corresponding HMM state sequence from the correct phoneme sequence q ^ which is the correct pronunciation sequence obtained in step S30. For example, the recognition error generation unit 4 refers to the HMM corresponding to each phoneme indicated by the acoustic model D6 and combines the HMM corresponding to each phoneme constituting the correct phoneme string q ^ to generate an HMM state sequence.

  An HMM is generally a finite state automaton having about 3 to 5 states, and a state constituting the model of the finite state automaton is accompanied by a self-transition. The number of self-transitions is the state duration, but here the number of self-transitions is still unknown. Accordingly, the recognition error generation unit 4 estimates the state duration length of each state included in the generated state sequence of the HMM. In the present embodiment, the recognition error generator 4 obtains the state duration length by sampling using a Gamma (gamma) distribution. The Gamma distribution is a distribution having a probability density function f (x) shown in the following formula (9).

  In equation (9), x is the duration of the HMM, θ is a scale parameter, and k is a model parameter called a shape parameter. Γ (k) represents a gamma function.

  The storage unit 8 stores, for each speaker, a state duration model D32 indicating a gamma distribution of state durations estimated in advance for each state of the HMM from speech data. The recognition error generation unit 4 uses the random number generator according to the gamma distribution of each state of the HMM indicated by the specific speaker state duration model D32 to generate each HMM constituting the state sequence of the HMM generated from the correct phoneme sequence q ^. Get an estimate of the state duration for. Thereby, a transition (path) between the states of each HMM is obtained. That is, the recognition error generation unit 4 concatenates HMMs using the obtained estimated value as a state duration, and obtains an HMM state sequence with a state duration.

(Step S32: HMM feature vector generation process)
The recognition error generation unit 4 obtains an acoustic feature quantity by sampling from a multivariate mixed Gauss distribution in each state of the HMM indicated by the acoustic model D6. Note that the multivariate mixed Gaussian distribution is a distribution having a probability density function Ν (x; μ, Σ) shown in Expression (10).

In Expression (10), x is an N-dimensional acoustic feature vector, and μ and Σ are the mean and covariance matrix of the multivariate Gaussian distribution, respectively.
Here, the HMM is determined by the mixed Gaussian distribution shown in Expression (11) using the multivariate mixed Gaussian distribution of the probability density function Ν (x; μ, Σ) shown in Expression (10).

C _m in the equation (11) is a weight for the multivariate mixed Gaussian distribution of the probability density function Ν (x; μ _m , Σ _m ), which is a mixing element, and satisfies the equation (12).

  In order to calculate output probabilities for acoustic features (features extracted from the short-time spectrum of speech), multivariate mixed Gaussian distributions of acoustic features in each state of the HMM previously obtained for each speaker are used as acoustic models. This is stored in the statistical model storage unit 31. The recognition error generation unit 4 obtains an acoustic feature amount corresponding to the state sequence of each HMM with a state duration by using a random number generator according to the multivariate mixed Gaussian distribution of each state of the HMM indicated by the acoustic model D6 (sampling). ).

(Step S33: linear conversion process)
The linear transformation process is optional. The recognition error generation unit 4 uses the feature amount conversion matrix D33 stored in advance in the storage unit 8 so that speech recognition is likely to cause confusion with respect to the acoustic feature amount obtained by sampling in step S32. Then, feature-space maximum like linear regression (fMLLR) is performed. This processing uses the technique described in the document “Y. Li et al. Incremental on-line feature space MLLR adaptation for telephony speech recognition, In ICSLP, 2002.”. In general, a statistical model such as an HMM forms an identification plane (a space that outputs a higher probability than other HMMs) in the acoustic feature space. Therefore, the discrimination performance can be intentionally deteriorated by separating the feature quantity from the discrimination plane (approaching it to another point somewhere far away) using linear transformation based on the feature quantity transformation matrix. As a point to be approached, a point obtained by replacing a phoneme with another phoneme that is statistically prone to error can be used.

(Step S34: Voice recognition processing)
Finally, the recognition error generation unit 4 recognizes the acoustic feature obtained in step S33 (or the acoustic feature obtained in step S32) using the acoustic model D6 and the language model D7, and recognizes the speech. Get results. The speech recognition result is n-best or word lattice. The speech recognition result includes a plurality of correct sentence candidates and the acoustic score and language score of each correct sentence candidate. The recognition error generation unit 4 writes the speech recognition result in the storage unit 8 as learning data D9.

[4.4 Step S4]
[4.4.1 Linguistic feature extraction processing]
In step S4, the error correction model learning unit 5 first extracts a feature function based on linguistic features used for error tendency learning from the speech / text data D4 and the learning data D9 stored in the storage unit 8. The rules of the feature function are, for example, linguistic features such as continuous words, phonemes constituting the words, two or more words that are not continuous, co-occurrence relationships between phonemes, syntactic information or semantic information of the words, etc. It is.

  In the present embodiment, the error correction model learning unit 5 determines, for example, the following (a) and (b) as feature functions based on word co-occurrence relationships.

(A) When the word string w includes a continuous word binary set (u, v), a function that returns the number (b) When the word string w includes a non-continuous word binary set (u, v) , A function that returns the number

  The error correction model learning unit 5 replaces each word constituting the word string w with a part-of-speech category such as a noun or a verb, and uses, for example, the following (c) and (d) as feature functions based on the syntax information. Determine. Note that c (•) is a function that maps words to parts of speech.

(C) a function that returns the number of part-of-speech binaries (c (u), c (v)) that are consecutive in the word string w (d) a part-of-speech binary pair that is not consecutive in the word string w (c ( u), c (v)), a function that returns the number if it is included

  Alternatively, the error correction model learning unit 5 replaces each word constituting the word string w with a category (semantic category) representing semantic information, and as a feature function based on semantic information, for example, the following (e) , (F) is defined. The semantic category can be obtained using a database external to the speech recognition apparatus 1 or a thesaurus stored in the storage unit 8. Note that s (•) is a function that maps words to semantic categories.

(E) a function that returns the number of semantic category binomials (s (u), s (v)) that are consecutive in the word string w (f) a semantic category binary group that is not consecutive in the word string w ( a function that returns the number of s (u), s (v))

  Further, the error correction model learning unit 5 determines, for example, the following (g) as a feature function related to a phoneme string.

(G) A function that returns the number of phoneme strings q in the word string w

The error correction model learning unit 5 extracts all feature functions in accordance with the above rules from the correct word string indicated by the text data of the speech / text data D4 and the speech recognition result of the learning data D9, and extracts the feature functions Counts the frequency of occurrences of The error correction model learning unit 5, the counted frequency of occurrence of the feature function is a predetermined threshold value or more is determined as a feature function f _i used in the error tendency.

[4.4.2 Error tendency learning process]
In the present embodiment, the error correction model learning unit 5 uses a risk minimization method described below in order to obtain an error correction model reflecting an error tendency.
Based on the risk minimization techniques, the statistical error correction model, speech x _{m (m} is an integer of 1 to M, M is the number of learning data) and, correct word sequence w _m which corresponds to the utterance x _{m, When 0} is given, the objective function L (Λ) is defined as the following equation (13).

L _m is a set of sentence hypotheses w _{m, 1} , w _{m, 2} ,... Generated by speech recognition from the utterance x _m, and the sentence hypothesis w _{m, k} (k is an integer of 1 or more) is the utterance x _m. The k-th correct sentence candidate word string. W _{m, 0} is the correct sentence of the utterance x _m , and R (w _{m, o} , w _{m, k} ) is the Levenshtein edit distance between the correct sentence w _{m, 0} and the sentence hypothesis w _{m, k.} . The posterior probability P (w _{m, k} | x _m ; Λ) is the posterior probability that the sentence hypothesis w _{m, k} is obtained when the utterance x _m occurs. Λ is a set of feature weights λ ₁ , λ ₂ ,... For the feature function, and Λ that minimizes the objective function of Equation (13) is a parameter of the error correction model to be obtained. This is because if Λ is estimated so as to minimize the objective function of Equation (13), the recognition error expected for the correct sentence candidate is minimized, and in speech recognition for unknown input speech different from the learning data, This is because recognition errors are similarly minimized by Λ and an improvement in speech recognition performance can be expected. That is, the objective function of Expression (13) is used as an evaluation function for calculating an evaluation value as to whether the feature weight is appropriate because the recognition error expected for the correct sentence candidate is minimized.

  The error correction model outputs an error score S (w) according to the following equation (14) for the sentence hypothesis w obtained for the speech input x.

  Accordingly, a speech recognition score {circumflex over (g)} (w | x) in consideration of the score of the error correction model is calculated as in the following equation (15), and among the sentence hypotheses obtained by speech recognition, the equation (15 ) Is output as a speech recognition result.

  In Expression (15), κ is the weight of the score of the language model with respect to the score P (x | w) of the acoustic model.

Note that the posterior probability P (w _{m, k} | x _m ; Λ) of the equation (13) is calculated as the following equation (16).

G ^ (w _{m, k} | x _m ; Λ) in the equation (16) is calculated from the equation (15) as the following equation (17).

S (w _{m, k} ) in equation (17) is calculated by equation (14) using the values of Λ = λ ₁ , λ ₂ ,.

  FIG. 5 is a diagram illustrating a processing flow of error correction model learning processing by the error correction model learning unit 5.

(Step S40: feature amount extraction process)
The error correction model learning unit 5 extracts a feature function f _i used in error tendency learning by the linguistic feature extraction process described above.

(Step S41: Model parameter initialization process)
The error correction model learning unit 5 initializes all the feature weights λ _i of the feature function f _i obtained in step S40 to zero.

(Step S42: Objective function calculation process)
The error correction model learning unit 5 reads the speech recognition result from the learning data D9, and reads the correct word string (text data) corresponding to the speech recognition result from the speech / text data D4. The error correction model learning unit 5 calculates the value of the objective function L (Λ) by using the current value of Λ = (λ ₁ , λ ₂ ,...) Using these read data and the equation (13). To do.

The sentence hypothesis w _{m, k} (k = 1,...) Is the kth correct sentence candidate included in the speech recognition result obtained from the speech data of the utterance x _m , and is obtained from the learning data D9. It is done. The correct answer sentence w _{m, 0} is a correct word string of the utterance x _m and is obtained from the voice / text data D4. The error correction model learning unit 5 uses the correct sentence w _{m, 0} read from the speech / text data D4 and the sentence hypothesis w _{m, k} read from the learning data D9 _, and the Levenshtein edit distance R ( w _{m, o} , w _{m, k} ) is calculated. In addition, the error correction model learning unit 5 calculates the posterior probability P (w _{m, k} | x _m ; Λ) according to the equations (16) and (17), but the acoustic score P (x in equation (17) _m | w _{m, k} ) and the language score P (w _{m, k} ) are obtained from the speech recognition result of the learning data D9. Further, the error correction model learning unit 5 calculates S (w _{m, k} ) of the equation (17) from the sentence hypothesis w _{m, k} for the feature function f _i extracted in step S40 and the current Λ. It calculates by Formula (14) using a value.

(Step S43: Parameter update process)
The error correction model learning unit 5 updates the parameter Λ of the error correction model based on the quasi-Newton method. In the quasi-Newton method, an appropriate initial value is given to generate the next value close to the solution, and the value close to the next solution is repeatedly generated from that value, and finally converges to the optimal solution. . See Non-Patent Document 1 for details of the quasi-Newton method.

(Step S44: End determination process)
The error correction model learning unit 5 compares the value of the objective function L (Λ) changed by updating the parameter with the value of the objective function L (Λ) before the change. The error correction model learning unit 5 repeats the process from step S42 if the value change is greater than or equal to a predetermined value, and executes the process of step S45 assuming that the update has converged if the change is smaller than the predetermined value.

(Step S45: Error correction model output process)
The error correction model learning unit 5 writes the error correction model D10 using the feature weight Λ = (λ ₀ , λ ₁ ,...) Of the error correction model when the update converges in the storage unit 8.

[4.5 Step S5]
The model integration unit 6 integrates the error correction model D10 generated in step S4 and the plurality of language models D8 selected from the statistical model storage unit 31 to generate an integrated model D11.

  In the speech recognition using the integrated model D11 obtained by the model integration unit 6 and the acoustic model, the speech recognition score g ^ (w | x) of the sentence hypothesis w is obtained for the speech input (input acoustic feature amount) x. The calculation is again performed as in the following equation (18).

P (x | w) in Expression (18) is a posterior probability indicating an acoustic likelihood for the sentence hypothesis w, and is an acoustic score. P _k (w) and P _r (w) are the language score of the kth language model and the language score of the rth language model obtained from the statistical model storage unit 31, respectively. Note that P _r (w) is the language score of the language model D7 used in the learning of the error correction model in step S4, and P _k (w) is the language score of the language model D8.
Θ _k ∈Θ is a mixture weight (model parameter) for each language model, and satisfies Σ _k θ _k = 1. The model integration unit 6 estimates the model parameter Θ. Expression (18) using the estimated model parameter Θ is an integrated model to be obtained.
That is, Expression (18) is obtained by adding the language score of each language model D8 according to the mixture weight to the language score portion of the error correction model shown in Expression (15) that reflects the error tendency of recognition errors obtained from the learning data. It is a linear interpolation.

Here, P _r (w) expΣ _i λ _i f _i (w) is replaced with P _r (w) to rearrange equation (18), then the speech recognition score g ^ (w) of the sentence hypothesis w is The following equation (19) is obtained.

  If P (w | x) is a conditional probability of the sentence hypothesis w when the speech input x is given, the following equation (20) is obtained.

Since the sum of probabilities is 1, the posterior probability P (w | x) of the sentence hypothesis _w is Z (Θ) ≡Σw _′ exp g ^ (w ′ | x) in the normalization term. The following equation (21) is given.

  Here, Z (Θ) is a constant for normalization and is calculated as shown in Equation (22).

However, w _t is all sentence hypotheses (correct answer candidates) obtained as a result of voice recognition of the voice input x.
Similar to the error correction model, the model parameter Θ is obtained by solving the risk minimization problem expressed by the following equation (23) using the development data D5 including N utterances.

Note that the optimization problem is made an unconstrained optimization problem using Lagrange coefficient ν> 0 so that the constraint condition Σ _k θ _k = 1 is satisfied.

  FIG. 6 is a diagram illustrating a processing flow of model integration processing by the model integration unit 6.

(Step S50: Model parameter initialization process)
The model integration unit 6 initializes the model parameter Θ. Here, the number of language models is K, and the model integration unit 6 initializes θ _k = 1 / K.

(Step S51: Objective function calculation process)
The model integration unit 6 reads the development data D5 from the storage unit 8. The model integration unit 6 recognizes the speech data of the development data D5 using the acoustic model D6 of the specific speaker, the language model D7, and the language model D8, and uses the value of the current model parameter Θ to formula (23) To calculate the value of the objective function L (Θ).
The sentence hypothesis w _{n, m} (m = 1,...) Is the mth correct sentence candidate of the utterance x _n indicated by the speech data of the development data D5. The correct sentence w _{n, 0} of the utterance x _n is obtained from the text data of the development data D5. The model integration unit 6 calculates the Levenshtein edit distance R (wn _{, o} , wn _{, m} ) in the equation (23) using the correct sentence wn _{, 0} of the utterance _{xn and} the sentence hypothesis wn _{, m.} To do.
Further, the posterior probability P (w _{n, m} | x _n ; Θ) in the equation (23) is a posterior probability that the correct sentence candidate wn _{, m} is obtained when the utterance x _n occurs, and the following equation ( 24).

ただし、ｇ＾（ｗ_ｎ，ｍ｜ｘ_ｎ；Θ）は、式（１８）から以下の式（２５）のように算出される。

However, g (w _{n, m} | x _n ; Θ) is calculated from the equation (18) as in the following equation (25).

In the equation (25), P (x _n | w _{n, m} ) (m = 1,...) Is an acoustic score of the sentence hypothesis w _{n, m} . P _k (w _{n, m} ) is a language score of the sentence hypothesis w _{n, m} when the language model D8 that is the k-th language model is used, and P _r (w _{n, m} ) is the language model D7. _Is the language score of sentence hypothesis wn _{, m} .

(Step S52: Model parameter update process)
The model integration unit 6 updates the model parameter Θ of the error correction model based on the quasi-Newton method.

(Step S53: End determination process)
The model integration unit 6 compares the objective function value changed by updating the parameter with the objective function value before the change, and repeats the processing from step S51 if the value change is greater than or equal to a predetermined value. If the update has converged, the process of step S54 is executed.

(Step S54: Integrated model output process)
The model integration unit 6 writes the equation (18) using the model parameters Θ = (θ ₀ , θ ₁ ,...) When the update converges in the storage unit 8 as the integration model D11.

[4.6 Step S5]
When voice data is input, the voice recognition unit 7 performs voice recognition in real time. The voice recognition unit 7 includes an integrated model D11 stored in the storage unit 8 corresponding to the speaker and topic of the input voice data, and an acoustic model stored in the statistical model storage unit 31 corresponding to the speaker. Using the model and the language model stored in the statistical model storage unit 31 corresponding to the topic, the correct sentence candidate of the input speech data and its score are obtained. The speech recognition unit 7 outputs speech recognition result data D12 indicating a correct sentence candidate having the best score.

[5. effect]
According to the present embodiment, since the speech recognition apparatus 1 can generate an integrated model in which information such as a speaker and a topic for which the recognition rate is to be improved is reflected in an error tendency, the speech recognition apparatus 1 recognizes more than conventional speech recognition. Errors are reduced.
In addition, since the speech recognition apparatus 1 integrates a plurality of language models after learning the error correction model, the speech recognition apparatus 1 can perform model learning more efficiently than before.

[6. Others]
The voice recognition device 1 described above has a computer system inside. The operation process of the speech recognition apparatus 1 is stored in a computer-readable recording medium in the form of a program, and the above processing is performed by the computer system reading and executing this program. The computer system here includes a CPU, various memories, an OS, and hardware such as peripheral devices.

Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case, and a program that holds a program for a certain period of time are also included. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

DESCRIPTION OF SYMBOLS 1 Speech recognition apparatus 2 Spoken language resource management part 21 Spoken language resource storage part 3 Statistical model management part 31 Statistical model storage part 4 Recognition error generation part 5 Error correction model learning part 6 Model integration part 7 Speech recognition part 8 Storage part

Claims (7)

A spoken language resource storage unit that stores voice data of an utterance of a specific speaker and text data that is a correct sentence corresponding to the voice data;
A statistical model storage unit for storing the acoustic model of the specific speaker and a language model for each topic;
A speech recognition unit that recognizes the speech data using the acoustic model of the specific speaker and the language model of the specific topic, and generates a speech recognition result including a recognition error;
An error correction model that statistically analyzes the tendency of recognition error from the speech recognition result generated by the recognition error generation unit and the correct sentence indicated by the text data, and corrects the tendency of the analyzed recognition error An error correction model learning unit for generating
Speech recognition of speech data different from the speech data used for generating the error correction model using the acoustic model of the specific speaker and the plurality of language models, and correct sentence candidates obtained by speech recognition, Based on a recognition error obtained by comparing correct sentences corresponding to different speech data, a statistical analysis is performed on a mixing weight when the plurality of language models are integrated into the error correction model generated by the error correction model learning unit. A model integration unit that generates an integrated model by integrating the language model of a topic different from the specific topic into the error correction model according to the calculated mixture weight;
A speech recognition apparatus comprising: The model integration unit includes the recognition error obtained from the correct sentence candidate, an acoustic score of the correct sentence candidate obtained by the error correction model, a language score in which the recognition error tendency is corrected, and the specific topic. Statistically calculating the mixing weight based on an evaluation value calculated by an evaluation function determined using a language score of the correct sentence candidate obtained from the language model of a topic different from
The speech recognition apparatus according to claim 1. The recognition error generation unit generates speech data by synthesizing speech content of the text data corresponding to the specific topic using the acoustic model of the specific speaker, and the generated speech data is used for the specific story. Generating a speech recognition result including a recognition error by performing speech recognition using the acoustic model of the person and the language model of the specific topic,
The speech recognition apparatus according to claim 1 or 2, wherein The error correction model represents linguistic features based on continuous words, phonemes constituting the words, non-consecutive words, co-occurrence relationships between phonemes, syntactic information of words, or semantic information of words. Defined using feature functions and their feature weights,
The error correction model learning unit includes the feature based on an evaluation value calculated by an evaluation function determined using a value of the feature function obtained from the speech recognition result and the recognition error included in the speech recognition result. A weight is calculated statistically, and the error correction model is generated using the calculated feature weight;
The speech recognition apparatus according to any one of claims 1 to 3, wherein A speech recognition unit that further recognizes speech data of the utterance of the specific topic by the specific speaker using the integrated model generated by the model integration unit;
The voice recognition device according to claim 1, wherein the voice recognition device is a voice recognition device. A spoken language resource storage process of storing voice data of a specific speaker's utterance and text data which is a correct sentence corresponding to the voice data;
A statistical model storing process for storing the acoustic model of the specific speaker and a language model for each topic;
A recognition error generation process for recognizing the speech data using the acoustic model of the specific speaker and the language model of a specific topic, and generating a speech recognition result including a recognition error;
An error correction model that statistically analyzes the tendency of recognition error from the speech recognition result generated in the recognition error generation process and the correct sentence indicated by the text data, and corrects the tendency of the analyzed recognition error An error correction model learning process to generate
Speech recognition of speech data different from the speech data used for generating the error correction model using the acoustic model of the specific speaker and the plurality of language models, and correct sentence candidates obtained by speech recognition, Based on a recognition error obtained by comparing correct sentences corresponding to different speech data, a statistical analysis is performed on a mixing weight when the plurality of language models are integrated into the error correction model generated in the error correction model learning process. A model integration step of generating an integrated model by integrating the language model of a topic different from the specific topic according to the calculated mixture weight into the error correction model;
An error correction model learning method characterized by comprising: Computer
Spoken language resource storage means for storing voice data of a specific speaker's utterance and text data which is a correct sentence corresponding to the voice data;
Statistical model storage means for storing the acoustic model of the specific speaker and a language model for each topic;
Recognition error generation means for recognizing the speech data using the acoustic model of the specific speaker and the language model of a specific topic, and generating a speech recognition result including a recognition error;
An error correction model that statistically analyzes the tendency of recognition error from the speech recognition result generated by the recognition error generation means and the correct sentence indicated by the text data, and corrects the tendency of the analyzed recognition error An error correction model learning means for generating
Speech recognition of speech data different from the speech data used for generating the error correction model using the acoustic model of the specific speaker and the plurality of language models, and correct sentence candidates obtained by speech recognition, Based on a recognition error obtained by comparing correct sentences corresponding to different speech data, a statistical analysis is performed on a mixture weight when the plurality of language models are integrated into the error correction model generated by the error correction model learning unit. A model integration unit that generates a unified model by integrating the language model of a topic different from the specific topic according to the calculated mixture weight into the error correction model;
A program for causing a voice recognition apparatus to function.

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