Removing noise from feature vectors
First Claim
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1. A method comprising:
- identifying a mixture of distributions that provide prior probabilities for combinations of clean signal feature vectors and obscuring feature vectors, the mixture of distributions comprising mixture components each comprising a mean and variance;
determining an observation variance for an observation probability that provides the probability of a noisy signal feature vector given a clean signal feature vector and at least one obscuring feature vector;
calculating a mean for a posterior probability distribution by applying a mean and a variance of a mixture component of the mixture of distributions that provide prior probabilities and the observation variance to a function;
using the mean of the posterior probability distribution to identify the clean signal feature vector; and
using the clean signal feature to identify a word during speech recognition.
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Abstract
A method and computer-readable medium are provided for identifying clean signal feature vectors from noisy signal feature vectors. One aspect of the invention includes using an iterative approach to identify the clean signal feature vector. Another aspect of the invention includes using the variance of a set of noise feature vectors and/or channel distortion feature vectors when identifying the clean signal feature vectors.
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Citations
17 Claims
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1. A method comprising:
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identifying a mixture of distributions that provide prior probabilities for combinations of clean signal feature vectors and obscuring feature vectors, the mixture of distributions comprising mixture components each comprising a mean and variance; determining an observation variance for an observation probability that provides the probability of a noisy signal feature vector given a clean signal feature vector and at least one obscuring feature vector; calculating a mean for a posterior probability distribution by applying a mean and a variance of a mixture component of the mixture of distributions that provide prior probabilities and the observation variance to a function; using the mean of the posterior probability distribution to identify the clean signal feature vector; and using the clean signal feature to identify a word during speech recognition. - View Dependent Claims (2, 3, 4, 5)
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6. A method comprising:
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accessing a prior mean for a distribution of training feature vectors that represents a prior probability of combinations of training feature vectors wherein the prior mean of the distribution of training feature vectors comprises a prior mean vector comprising elements representing a mean of a mixture component of a mixture of distributions for clean signal feature vectors and elements representing a mean of a mixture component of a mixture of distributions for noise training feature vectors; setting an initial value for a posterior mean vector comprising elements for a component of a clean signal feature vector and elements for a component of a noise feature vector; determining a revised value for the posterior mean vector based in part on the initial value for the posterior mean vector, a difference between the prior mean vector and the initial value for the posterior mean vector, and a noisy signal feature vector, wherein the noisy signal feature vector represents a noisy signal that is a combination of a clean signal with at least one of a group comprising a noise signal and channel distortion; determining whether to accept the revised value as a final value for the posterior mean vector; using the final value for the posterior mean vector to identify a clean signal feature vector; and using the clean signal feature vector to recognize a word during speech recognition. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A computer-readable storage medium having encoded thereon computer-executable instructions that when executed by a processor cause the processor to perform steps comprising:
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accessing a noisy signal feature vector that represents a noisy signal which is a combination of a clean signal with at least one of a group comprising noise and channel distortion; accessing prior mean vector for at least one distribution of training feature vectors wherein accessing a prior mean vector comprises accessing a prior mean vector comprising elements representing a mean vector for a distribution of noise training feature vectors described in part by a variance, and elements representing a mean vector for a distribution of clean signal training feature vectors; identifying an initial value for a posterior mean vector comprising elements for a clean signal feature vector and elements for a noise feature vector; and performing iterations to identify a final value for the posterior mean vector, each iteration performing a calculation based on the noisy signal feature vector, the difference between the prior mean vector and a current value for the posterior mean vector, and the current value for the posterior mean vector, the current value for the posterior mean vector being updated with each iteration; using the final value for the posterior mean vector to identify a clean signal feature vector; and using the clean signal feature vector in speech recognition to recognize a word. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification