Data processing: speech signal processing – linguistics – language – Speech signal processing – For storage or transmission
Reexamination Certificate
2006-06-05
2008-05-06
Knepper, David D. (Department: 2626)
Data processing: speech signal processing, linguistics, language
Speech signal processing
For storage or transmission
C379S392010
Reexamination Certificate
active
07369990
ABSTRACT:
Acoustic noise for wireless or landline telephony is reduced through optimal filtering in which each frequency band of every time frame is filtered as a function of the estimated signal-to-noise ratio and the estimated total noise energy for the frame. Non-speech bands, non-speech frames and other special frames are further attenuated by one or more predetermined multiplier values. Noise in a transmitted signal formed of frames each formed of frequency bands is reduced. A respective total signal energy and a respective current estimate of the noise energy for at least one of the frequency bands is determined. A respective local signal-to-noise ratio for at least one of the frequency bands is determined as a function of the respective signal energy and the respective current estimate of the noise energy. A respective smoothed signal-to-noise ratio is determined from the respective local signal-to-noise ratio and another respective signal-to-noise ratio estimated for a previous frame. A respective filter gain value is calculated for the frequency band from the respective smoothed signal-to-noise ratio. Also, it is determined whether at least a respective one as a plurality of frames is a non-speech frame. When the frame is a non-speech frame, a noise energy level of at least one of the frequency bands of the frame is estimated. The band is filtered as a function of the estimated noise energy level.
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Knepper David D.
Mintz Levin Cohn Ferris Glovsky and Popeo PC
Nortel Networks Limited
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