Apparatus and methods for the selective addition of noise to templates employed in automatic speech recognition systems
First Claim
1. In a speech recognition system of the type including a storage for storing initial templates representing spectral values of recognizable speech in the absence of noise, a spectrum analyzer for providing spectral values of utterances of an incoming signal representing speech in the presence of noise at an output thereof, and a recognition module for comparing operational templates with the output spectral values from said spectrum analyzer to provide an output upon a favorable comparison indicative of the presence of recognized speech in said utterances, the improvement therewith of apparatus for generating said operation templates, comprising:
- first means coupled to said spectrum analyzer for providing an estimated noise signal indicative of the noise in the incoming signal, and second means coupled to said first means and responsive to said estimated noise signal to generate said operational templates which are modified from said initial templates according to said estimated noise signal,wherein said first means includes a speech and noise level tracking means having a speech tracking portion operative to detect a speech signal in the presence of noise in said utterances and to provide at one output thereof a first signal indicative of an average power of the speech signal in the presence of noise which is a scalar speech level value associated with the speech signal, and a noise tracking portion operative to detect noise in said utterances and to provide a given time period of said utterances which is a vector of spectral values representing an estimate of the noise, andwherein said second means generates said operational templates by adjusting the speech level of said initial templates in accordance with said first signal and by adding spectral values of the estimate of the noise in accordance with said second signal to said initial templates,whereby the operational templates have the estimated noise of and the same signal-to-noise ratio as the utterances of the incoming signal in order to obtain an improved speech recognition performance of said recognition module.
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Abstract
To improve the recognition of incoming speech signals in noise, the prestored templates of noise-free speech are modified to have the estimated spectral values of noise and the same signal-to-noise ratio as the incoming signal.
98 Citations
15 Claims
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1. In a speech recognition system of the type including a storage for storing initial templates representing spectral values of recognizable speech in the absence of noise, a spectrum analyzer for providing spectral values of utterances of an incoming signal representing speech in the presence of noise at an output thereof, and a recognition module for comparing operational templates with the output spectral values from said spectrum analyzer to provide an output upon a favorable comparison indicative of the presence of recognized speech in said utterances, the improvement therewith of apparatus for generating said operation templates, comprising:
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first means coupled to said spectrum analyzer for providing an estimated noise signal indicative of the noise in the incoming signal, and second means coupled to said first means and responsive to said estimated noise signal to generate said operational templates which are modified from said initial templates according to said estimated noise signal, wherein said first means includes a speech and noise level tracking means having a speech tracking portion operative to detect a speech signal in the presence of noise in said utterances and to provide at one output thereof a first signal indicative of an average power of the speech signal in the presence of noise which is a scalar speech level value associated with the speech signal, and a noise tracking portion operative to detect noise in said utterances and to provide a given time period of said utterances which is a vector of spectral values representing an estimate of the noise, and wherein said second means generates said operational templates by adjusting the speech level of said initial templates in accordance with said first signal and by adding spectral values of the estimate of the noise in accordance with said second signal to said initial templates, whereby the operational templates have the estimated noise of and the same signal-to-noise ratio as the utterances of the incoming signal in order to obtain an improved speech recognition performance of said recognition module. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of forming operational templates for use in a speech recognition system for recognizing speech in the presence of noise in utterances of an incoming signal based upon comparison of spectral values thereof to the operational templates, comprising the steps of:
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providing an estimated noise signal by detecting a speech signal in the presence of noise in the incoming signal and providing a first signal indicative of an average power of the speech signal in the presence of noise which is a scalar speech level value associated with the speech signal, and detecting noise in said utterances and providing a second signal indicative of an average power of the noise over a given time period of said utterances which is a vector of spectral values representing an estimate of the noise, and modifying initial templates representing recognizable speech in the absence of noise by adjusting the speech level of said initial templates in accordance with said first signal and by adding spectral values of the estimate of the noise in accordance with said second signal to said initial templates, in order to form said operational templates having the estimated noise of and the same signal-to-noise ratio as the utterances of the incoming signal for obtaining an improved speech recognition performance. - View Dependent Claims (13, 14, 15)
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Specification