Method and apparatus for processing speech signals

Claim 1

A method of enhancing pitch detection in sampled speech signals by performing time domain speech envelope flattening, comprising the steps of: receiving a sampled time domain speech signal; deriving a time domain speech envelope from said sampled speech signal by performing the steps of: detecting peak signal levels in said sampled time domain speech signal, and filtering said detected peak signal levels to produce said time domain speech envelope signal from said peak signal levels of said speech signal; creating a sampled amplitude function by performing the steps of: sampling said time domain speech envelope at a sampling rate lower than a sampling rate for said sampled time domain speech signal to produce subrate samples; computing a plurality of interpolated points by interpolating values between adjacent ones of said subrate samples to produce interpolated values; generating a sampled amplitude function having a sample point corresponding to each sample of said sampled speech signal by assigning said subrate samples to corresponding amplitude function samples and assigning said interpolated values to each sample point located between said sample points; and normalizing said sampled time domain speech signal to produce time domain speech envelope flattening by performing a point by point division of said time domain speech signal samples by said corresponding amplitude function samples.

Claim 2

A method of enhancing pitch detection in sampled speech signals by performing time domain speech envelope flattening, comprising the steps of: receiving a sampled time domain speech signal; deriving a time domain speech envelope from said sampled speech signal by performing the steps of: detecting peak signal levels in said sampled time domain speech signal, and filtering said detected peak signal levels to produce said time domain speech envelope signal from said peak signal levels of said speech signal; creating a sampled amplitude function by performing the steps of: sampling said time domain speech envelope at a sampling rate lower than a sampling rate for said sampled time domain speech signal to produce subrate samples; computing a plurality of interpolated points by interpolating values between adjacent ones of said subrate samples to produce interpolated values; generating a sampled amplitude function having a sample point corresponding to each sample of said sampled speech signal by assigning said subrate samples to corresponding amplitude function samples and assigning said interpolated values to each sample point located between said sample points; and normalizing said sampled time domain speech signal to produce time domain speech envelope flattening by performing a point by point division of said time domain speech signal samples by said corresponding amplitude function samples.

Claim 4

A method of enhancing pitch detection in sampled speech signals by performing time domain speech envelope flattening, comprising the steps of: receiving a sampled time domain speech signal; deriving a time domain speech envelope from said sampled speech signal; creating a sampled amplitude function by performing the steps of: sampling said time domain speech envelope at a sampling rate lower than a sampling rate for said sampled time domain speech signal to produce subrate samples; computing a plurality of interpolated points by interpolating values between adjacent ones of said subrate samples to produce interpolated values; generating a sampled amplitude function having a sample point corresponding to each sample of said sampled speech signal by assigning said subrate samples to corresponding amplitude function samples and assigning said interpolated values to each sample point located between said sample points; and normalizing said sampled time domain speech signal with the sampled amplitude function; and to produce time domain speech envelope flattening.

Claim 5

A method of enhancing pitch detection in sampled speech signals by performing time domain speech envelope flattening, comprising the steps of: receiving a sampled time domain speech signal; deriving a time domain speech envelope from said sampled speech signal; creating a sampled amplitude function by performing the steps of: sampling said time domain speech envelope at a sampling rate lower than a sampling rate for said sampled time domain speech signal to produce subrate samples; computing a plurality of interpolated points by interpolating values between adjacent ones of said subrate samples to produce interpolated values; generating a sampled amplitude function having a sample point corresponding to each sample of said sampled speech signal by assigning said subrate samples to corresponding amplitude function samples and assigning said interpolated values to each sample point located between said sample points; and normalizing said sampled time domain speech signal with the sampled amplitude function; and to produce time domain speech envelope flattening.

Claim 9

A method of enhancing pitch detection in sampled speech signals by performing time domain speech envelope flattening, comprising the steps of: receiving a sampled time domain speech signal; deriving a time domain speech envelope from said sampled speech signal by sampling said time domain speech envelope at a rate lower than a sampling rate for said sampled time domain speech signal; creating a sampled amplitude function having a sample point corresponding to each sample of said sampled speech signal by assigning said subrate samples to corresponding amplitude function samples and assigning interpolated values to each sample point located between said sample points; and normalizing said sampled time domain speech signal with the sampled amplitude function to produce time domain speech envelope flattening.

Claim 10

A method of enhancing pitch detection in sampled speech signals by performing time domain speech envelope flattening, comprising the steps of: receiving a sampled time domain speech signal; deriving a time domain speech envelope from said sampled speech signal by sampling said time domain speech envelope at a rate lower than a sampling rate for said sampled time domain speech signal; creating a sampled amplitude function having a sample point corresponding to each sample of said sampled speech signal by assigning said subrate samples to corresponding amplitude function samples and assigning interpolated values to each sample point located between said sample points; and normalizing said sampled time domain speech signal with the sampled amplitude function to produce time domain speech envelope flattening.

Claim 11

A method of enhancing pitch detection in sampled speech signals by performing time domain speech envelope flattening, comprising the steps of: receiving a sampled time domain speech signal; deriving a time domain speech envelope from said sampled speed signal by performing the steps of: detecting peak signal levels in said sampled time domain speech signal, and low pass filtering said detected peak signal levels with a low pass filter having a cutoff frequency between approximately 25 and 300 Hz to produce said time domain speech envelope signal from said peak signal levels of said speech signal; creating a sampled amplitude function by performing the steps of: sampling said time domain speech envelope at a sampling rate between approximately 100 and 1000 Hz to produce subrate samples; computing a plurality of interpolated points by linear interpolating values between adjacent ones of said subrate samples using a low pass filter to produce interpolated values; generating a sampled amplitude function having a sample point corresponding to each sample of said sampled speech signal by assigning said subrate samples to corresponding amplitude function samples and assigning said interpolated values to each sample point located between said sample points; normalizing said sampled time domain speech signal to produce time domain speech envelope flattening by performing a point by point division of said time domain speech signal samples by said corresponding amplitude function samples; and pitch detecting said normalized signals.

Claim 12

A method of enhancing pitch detection in sampled speech signals by performing time domain speech envelope flattening, comprising the steps of: receiving a sampled time domain speech signal; deriving a time domain speech envelope from said sampled speed signal by performing the steps of: detecting peak signal levels in said sampled time domain speech signal, and low pass filtering said detected peak signal levels with a low pass filter having a cutoff frequency between approximately 25 and 300 Hz to produce said time domain speech envelope signal from said peak signal levels of said speech signal; creating a sampled amplitude function by performing the steps of: sampling said time domain speech envelope at a sampling rate between approximately 100 and 1000 Hz to produce subrate samples; computing a plurality of interpolated points by linear interpolating values between adjacent ones of said subrate samples using a low pass filter to produce interpolated values; generating a sampled amplitude function having a sample point corresponding to each sample of said sampled speech signal by assigning said subrate samples to corresponding amplitude function samples and assigning said interpolated values to each sample point located between said sample points; normalizing said sampled time domain speech signal to produce time domain speech envelope flattening by performing a point by point division of said time domain speech signal samples by said corresponding amplitude function samples; and pitch detecting said normalized signals.