Electronics and Telecommunications Research Institute

Yunkeun Lee

Hoon Chung

Jeon Gue Park

Byung Ok Kang

Sung Joo Lee

Jeom Ja Kang

Ho-Young Jung

Hyung-Bae Jeon

Ji Hyun Wang

Euisok Chung

Jong Jin Kim

Ki-young Park

Kap Kee Kim

Hoon-Young Cho

A speech recognition system includes: a speed level classifier for measuring a moving speed of a moving object by using a noise signal at an initial time of speech recognition to determine a speed level of the moving object; a first speech enhancement unit for enhancing sound quality of an input speech signal of the speech recognition by using a Wiener filter, if the speed level of the moving object is equal to or lower than a specific level; and a second speech enhancement unit enhancing the sound quality of the input speech signal by using a Gaussian mixture model, if the speed level of the moving object is higher than the specific level. The system further includes an end point detection unit for detecting start and end points, an elimination unit for eliminating sudden noise components based on a sudden noise Gaussian mixture model.

Noise reduction for speech recognition in a moving vehicle

An utterance verification method for an isolated word N-best speech recognition result includes: calculating log likelihoods of a context-dependent phoneme and an anti-phoneme model based on an N-best speech recognition result for an input utterance; measuring a confidence score of an N-best speech-recognized word using the log likelihoods; calculating distance between phonemes for the N-best speech-recognized word; comparing the confidence score with a threshold and the distance with a predetermined mean of distances; and accepting the N-best speech-recognized word when the compared results for the confidence score and the distance correspond to acceptance.

Utterance verification method and apparatus for isolated word N-best recognition result

A Viterbi decoder includes: an observation vector sequence generator for generating an observation vector sequence by converting an input speech to a sequence of observation vectors; a local optimal state calculator for obtaining a partial state sequence having a maximum similarity up to a current observation vector as an optimal state; an observation probability calculator for obtaining, as a current observation probability, a probability for observing the current observation vector in the optimal state; a buffer for storing therein a specific number of previous observation probabilities; a non-linear filter for calculating a filtered probability by using the previous observation probabilities stored in the buffer and the current observation probability; and a maximum likelihood calculator for calculating a partial maximum likelihood by using the filtered probability. The filtered probability may be a maximum value, a mean value or a median value of the previous observation probabilities and the current observation probability.

Viterbi decoder and speech recognition method using same using non-linear filter for observation probabilities

A noise cancellation apparatus includes a noise estimation module for receiving a noise-containing input speech, and estimating a noise therefrom to output the estimated noise; a first Wiener filter module for receiving the input speech, and applying a first Wiener filter thereto to output a first estimation of clean speech; a database for storing data of a Gaussian mixture model for modeling clean speech; and an MMSE estimation module for receiving the first estimation of clean speech and the data of the Gaussian mixture model to output a second estimation of clean speech. The apparatus further includes a final clean speech estimation module for receiving the second estimation of clean speech from the MMSE estimation module and the estimated noise from the noise estimation module, and obtaining a final Wiener filter gain therefrom to output a final estimation of clean speech by applying the final Wiener filter gain.

Noise cancellation system and method

An apparatus for evaluating the performance of speech recognition includes a speech database for storing N-number of test speech signals for evaluation. A speech recognizer is located in an actual environment and executes the speech recognition of the test speech signals reproduced using a loud speaker from the speech database in the actual environment to produce speech recognition results. A performance evaluation module evaluates the performance of the speech recognition by comparing correct recognition results answers with the speech recognition results.

Apparatus and method for evaluating performance of speech recognition

A speech recognition apparatus generates a feature vector series corresponding to a speech signal, and recognizes a phoneme series corresponding to the feature vector series using sounds corresponding to phonemes and a phoneme language model. In addition, the speech recognition apparatus recognizes vocabulary that corresponds to the recognized phoneme series. At this time, the phoneme language model represents connection relationships between the phonemes, and is modeled according to time-variant characteristics of the phonemes.

Human speech recognition apparatus and method

A speech recognition system for a mobile terminal includes an acoustic variation channel unit and a pronunciation channel unit. The acoustic variation channel unit transforms a speech signal into feature parameters and Viterbi-decodes the speech signal to produce a varied phoneme sequence by using the feature parameters and predetermined models. Further, the pronunciation variation channel unit Viterbi-decodes the varied phoneme sequence to produce a word phoneme sequence by using the varied phoneme sequence and a preset DHMM (Discrete Hidden Markov Model) based context-dependent error model.

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Daejeon, South Korea

Yunkeun Lee