Speech analyzer-synthesizer system employing improved formant extractor

Claim 2

Speech analysis apparatus for locating formants of a voiced speech signal, which comprises: means supplied with a speech signal for developing a signal representative of a smoothed spectral envelope thereof, means supplied with said spectral envelope signal for developing signals representative of the location and amplitude of peaks within assigned frequency ranges in said speech signal, said ranges being selected to encompass a prescribed frequency range of said speech signal with predetermined segments of overlap and means responsive to said peak representative signals for selecting as formants of said speech signal the highest amplitude peaks according to location within said ranges.

Claim 3

Speech analysis apparatus for locating formants of voiced speech signals, which comprises: means for developing a signal representative of the cepstrum of an applied speech signal, means for developing from said cepstrum signal a signal representative of the spectral envelope of said speech signal, means for evaluating said spectral envelope signal along a contour close to the pole locations in the complex frequency plane thereby to produce a signal in which spectrum peaks are sharpened, means responsive both to said spectral envelope signal and selectively to said cepstrum signal for developing signals representative of the location and amplitude of all peaks in said spectral envelope signal, means responsive to said peak location signal for selecting and ordering in frequency the highest of said amplitude peaks, and means for identifying said selected and ordered peak location signals as formants of said applied signal.

Claim 4

Speech analysis apparatus for locating formants of voiced speech signals, which comprises: means for developing a signal representative of the cepstrum of an applied speech signal, means for developing from said cepstrum signal a signal representative of the spectral envelope of said speech signal, means for evaluating said spectral envelope signal along a contour close to the pole locations in the complex frequency plane thereby to produce a signal in which spectrum peaks are sharpened, means responsive both to said spectral envelope signal and selectively to said cepstrum signal for developing signals representative of the location and amplitude of all peaks in said spectral envelope signal, means responsive to said peak location signal for selecting and ordering in frequency the highest of said amplitude peaks, and means for identifying said selected and ordered peak location signals as formants of said applied signal.

Claim 5

Speech analysis apparatus for locating formants of a voiced speech signal, which comprises: means for developing a signal representative of the smoothed spectral envelope of an applied speech signal, means for locating all peaks in said spectral envelope signal, means for developing signals representative of the location and amplitude of each of said located peaks within assigned frequency ranges, said ranges being selected to encompass a selected frequency range of said applied signal with prescribed segments of overlap, means responsive to said peak location signals for selecting the highest amplitude peak in each of said ranges, means for identifying as formants of said applied signal said selected peaks which occur in nonoverlapping segments of said ranges, and means for identifying as formants of said applies signal the highest amplitude peaks according to their location, which occur in overlapping segments of said ranges.

Claim 6

Speech analysis apparatus for locating formants of a voiced speech signal, which comprises: means for developing a signal representative of the smoothed spectral envelope of an applied speech signal, means for locating all peaks in said spectral envelope signal, means for developing signals representative of the location and amplitude of each of said located peaks within assigned frequency ranges, said ranges being selected to encompass a selected frequency range of said applied signal with prescribed segments of overlap, means responsive to said peak location signals for selecting the highest amplitude peak in each of said ranges, means for identifying as formants of said applied signal said selected peaks which occur in nonoverlapping segments of said ranges, and means for identifying as formants of said applies signal the highest amplitude peaks according to their location, which occur in overlapping segments of said ranges.

Claim 7

Apparatus as defined in claim 3, in combination with, spectral analysis means for enhancing said peaks in said spectral envelope signal.

Claim 8

Speech analysis apparatus for locating formants of voiced speech signals, which comprises: means for developing a signal representative of the pitch period of an applied speech signal, means for selectively weighting said applied speech signals with a symmetric window function of said pitch period signal, means supplied with said weighted speech signal for developing a signal representative of the smoothed spectral envelope of said applies speech signal, means for locating all peaks in said spectral envelope signal, means for developing signals representative of the location and amplitude of each of said located peaks within assigned frequency ranges, means responsive to said peak location signals for selecting the highest amplitude peak in each of said ranges, means for identifying as formants of said applied signal said selected peaks which occur in nonoverlapping segments of said ranges, and means for identifying as formants of said applied signal the highest amplitude peaks according to their location, which occur in overlapping segments of said ranges.

Claim 9

Speech analysis apparatus for locating formants of voiced speech signals, which comprises: means for developing a signal representative of the pitch period of an applied speech signal, means for selectively weighting said applied speech signals with a symmetric window function of said pitch period signal, means supplied with said weighted speech signal for developing a signal representative of the smoothed spectral envelope of said applies speech signal, means for locating all peaks in said spectral envelope signal, means for developing signals representative of the location and amplitude of each of said located peaks within assigned frequency ranges, means responsive to said peak location signals for selecting the highest amplitude peak in each of said ranges, means for identifying as formants of said applied signal said selected peaks which occur in nonoverlapping segments of said ranges, and means for identifying as formants of said applied signal the highest amplitude peaks according to their location, which occur in overlapping segments of said ranges.

Claim 10

Apparatus as defined in claim 5 wherein said applied speech signals are weighted with a window function with a duration of approximately three times the pitch period of said applied speech signals.

Claim 11

Apparatus for analyzing speech frequency signals, which comprises: means for counting the zero axis crossings of an applied speech signal, means for developing a signal representative of the cepstrum of said speech signal, and means responsive to said zero crossing count and to said cepstrum signal for determining therefrom the voiced-unvoiced character of said speech signal and, if voiced, the pitch period of said signal.

Claim 12

Apparatus for analyzing speech frequency signals, which comprises: means for counting the zero axis crossings of an applied speech signal, means for developing a signal representative of the cepstrum of said speech signal, and means responsive to said zero crossing count and to said cepstrum signal for determining therefrom the voiced-unvoiced character of said speech signal and, if voiced, the pitch period of said signal.

Claim 13

A speech signal analyzer system for producing coded signals from applied speech signals, which comprises: means for developing a signal representative of the smoothed spectrum of an applied speech signal, means for locating all peaks in said spectrum, means responsive to said located peaks and selectively to said spectrum for developing, during voiced intervals of said speech signal, control signals represeNtative of the location of the highest of said spectrum peaks in a prescribed order as formants of said applied signal, means responsive to said spectrum for developing control signals representative of the level of said applied signal during voiced and unvoiced intervals, respectively, means for developing a signal representative of the cepstrum of said applied speech signal, means responsive to a count of zero axis crossings in said applied signal and to said cepstrum for developing a signal representative of the voicing character of said applied signal and the pitch period of voiced intervals thereof, means responsive to said peak signals for developing a signal representative of the pole and zero locations for unvoiced intervals of said applied signal, and means for utilizing all of said developed signals as a coded representation of said applied speech signal.

Claim 14

A speech signal analyzer system for producing coded signals from applied speech signals, which comprises: means for developing a signal representative of the smoothed spectrum of an applied speech signal, means for locating all peaks in said spectrum, means responsive to said located peaks and selectively to said spectrum for developing, during voiced intervals of said speech signal, control signals represeNtative of the location of the highest of said spectrum peaks in a prescribed order as formants of said applied signal, means responsive to said spectrum for developing control signals representative of the level of said applied signal during voiced and unvoiced intervals, respectively, means for developing a signal representative of the cepstrum of said applied speech signal, means responsive to a count of zero axis crossings in said applied signal and to said cepstrum for developing a signal representative of the voicing character of said applied signal and the pitch period of voiced intervals thereof, means responsive to said peak signals for developing a signal representative of the pole and zero locations for unvoiced intervals of said applied signal, and means for utilizing all of said developed signals as a coded representation of said applied speech signal.

Claim 15

A speech signal analyzer-synthesizer system with reduced channel bandwidth requirements, which comprises: at an analyzer station, means for developing a signal representative of the smoothed spectrum of an applied speech signal, means for locating all peaks in said spectrum, means responsive to an indication of said located peaks and selectively to said spectrum signal for developing, during voiced intervals of said speech signal, control signals representative of the location of the highest of said amplitude peaks in a prescribed order as formants of said applied signal, means responsive to said spectrum signal for developing signals representative of the level of said applied signal during voiced and unvoiced intervals, respectively, means for developing a signal representative of the cepstrum of said applied signal, means responsive to a count of zero axis crossings in said applied signal and to said cepstrum signal for developing signals representative of the voicing character of said applied signal and the pitch period of voiced intervals thereof, means responsive to said peak signals for developing signals representative of the pole and zero locations for unvoiced intervals of said applied signal, and means responsive to all of said developed signals for delivering them to a synthesizer station, and at said synthesizer station, means responsive to received unvoiced level control signals for adjusting the level of a source of noise signals, a system of unvoiced resonant circuits energized by said adjusted noise signals, means for adjusting said resonant system with said pole and zero location signals to produce an unvoiced signal, generator means responsive to said pitch period control signal for developing pulses at pitch frequency, means for adjusting the amplitude of said pulses according to said level control signal during voiced signals of said applied signal, a system of resonant circuits energized by said control pulse signals and by said formant signals to produce a voiced signal, means for combining said voiced and unvoiced signals, means for shaping the spectrum of said combined signal, and means for utilizing said shaped spectrum signal as a replica of said applied speech signal.

Claim 16

A speech signal analyzer-synthesizer system with reduced channel bandwidth requirements, which comprises: at an analyzer station, means for developing a signal representative of the smoothed spectrum of an applied speech signal, means for locating all peaks in said spectrum, means responsive to an indication of said located peaks and selectively to said spectrum signal for developing, during voiced intervals of said speech signal, control signals representative of the location of the highest of said amplitude peaks in a prescribed order as formants of said applied signal, means responsive to said spectrum signal for developing signals representative of the level of said applied signal during voiced and unvoiced intervals, respectively, means for developing a signal representative of the cepstrum of said applied signal, means responsive to a count of zero axis crossings in said applied signal and to said cepstrum signal for developing signals representative of the voicing character of said applied signal and the pitch period of voiced intervals thereof, means responsive to said peak signals for developing signals representative of the pole and zero locations for unvoiced intervals of said applied signal, and means responsive to all of said developed signals for delivering them to a synthesizer station, and at said synthesizer station, means responsive to received unvoiced level control signals for adjusting the level of a source of noise signals, a system of unvoiced resonant circuits energized by said adjusted noise signals, means for adjusting said resonant system with said pole and zero location signals to produce an unvoiced signal, generator means responsive to said pitch period control signal for developing pulses at pitch frequency, means for adjusting the amplitude of said pulses according to said level control signal during voiced signals of said applied signal, a system of resonant circuits energized by said control pulse signals and by said formant signals to produce a voiced signal, means for combining said voiced and unvoiced signals, means for shaping the spectrum of said combined signal, and means for utilizing said shaped spectrum signal as a replica of said applied speech signal.