Speech analyzer comprising circuits for calculating autocorrelation coefficients forwardly and backwardly
First Claim
1. A speech analyzer for analyzing an input speech sound signal representative of speech sound of an input speech sound waveform into a plurality of signals of a first group representative of a preselected one of spectral distribution information and spectral envelope information of said speech sound waveform and at least two signals of a second group representative of sound source information of said speech sound, said speech sound having a pitch period of a value variable between a shortest and a longest pitch period, said speech analyzer comprising:
- window processing means for processing said input speech sound signal into a sequence of a predetermined number of windowed samples, said sequence lasting each of a series of predetermined window periods, said windowed samples being representative of the speech sound in said each window period and equally spaced with respect to time between a leading and a trailing end of said each window period;
first means connected to said window processing means for processing said windowed sample sequences into said first-group signals and a first of said second-group signals, said first signal being representative of amplitude information of the speech sound in the respective window periods;
average power calculating means operatively coupled to said first means for calculating with reference to said first signal an average power of the speech sound at least for said each window period and one of said window periods that next precedes said each window period in said series;
increasing rate calculating means connected to said average power calculating means for calculating for said each window period a rate of increase of the average power calculated for said each window period relative to the average power calculated for said next preceding window period to produce a control signal having a first and a second value when the rate of increase calculated for said each window period is greater and less than a preselected value, respectively;
second means connected to said window processing means and said increasing rate calculating means for calculating a plurality of autocorrelation coefficients for a plurality of joining intervals, respectively, by the use of reference members and joint members, said joining intervals differing from one another by the equal spacing between two successive ones of said windowed samples and including a shortest and a longest joining interval which are decided in accordance with said shortest and said longest pitch periods, respectively, said reference members being those prescribed ones of said windowed samples which are successively distributed throughout a reference fraction of said each window period, said reference fraction being placed farther with respect to time from the leading and the trailing ends of said each window period when said control signal has said first and said second values, respectively, said joint members being those sets of windowed samples, the windowed samples of each set being equal in number to said prescribed samples, which are successively distributed throughout a plurality of joint fractions of said each window period, respectively, said joint fractions being displaced in said each window period from said reference fraction by said joining intervals, respectively, farther from the trailing and the leading ends of said each window period when said control signal has said first and said second values, respectively; and
third means connected to said second means for producing a second of said second-group signals by finding a greatest value of the autocorrelation coefficients calculated for the respective joining intervals for said each window period and making said second signal represent those joining intervals as the pitch periods of the speech sound in the respective window periods for which the autocorrelation coefficients having the greatest values are calculated for the respective window periods.
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Abstract
A speech analyzer with improved pitch period extraction and improved accuracy of voiced/unvoiced decision comprises circuits for calculating autocorrelation coefficients forwardly and backwardly with respect to time. Reference members for the forward and the backward calculation are those successively prescribed ones of windowed samples of a signal representative of speech sound which are placed in each window period farther from a trailing and a leading end thereof, respectively. Members to be joined to the respective reference members for forward and backward calculation of each autocorrelation coefficient are displaced therefrom by a joining interval farther from the leading and the trailing ends, respectively. The joining interval is varied between a shortest and a longest pitch period of the speech sound stepwise by a spacing between two successive windowed samples. One of the joining intervals for which the greatest of the autocorrelation coefficients is calculated during each window period gives a better pitch period for that period than ever obtained. The circuits may comprise a circuit for calculating a rate of increase of an average power of the speech sound in each window period and an autocorrelator for carrying out the forward and the backward calculation when the rate is less and greater than a preselected value, respectively. Alternatively, the circuits may comprise two autocorrelators, one for the forward calculation and the other for the backward calculation.
278 Citations
4 Claims
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1. A speech analyzer for analyzing an input speech sound signal representative of speech sound of an input speech sound waveform into a plurality of signals of a first group representative of a preselected one of spectral distribution information and spectral envelope information of said speech sound waveform and at least two signals of a second group representative of sound source information of said speech sound, said speech sound having a pitch period of a value variable between a shortest and a longest pitch period, said speech analyzer comprising:
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window processing means for processing said input speech sound signal into a sequence of a predetermined number of windowed samples, said sequence lasting each of a series of predetermined window periods, said windowed samples being representative of the speech sound in said each window period and equally spaced with respect to time between a leading and a trailing end of said each window period; first means connected to said window processing means for processing said windowed sample sequences into said first-group signals and a first of said second-group signals, said first signal being representative of amplitude information of the speech sound in the respective window periods; average power calculating means operatively coupled to said first means for calculating with reference to said first signal an average power of the speech sound at least for said each window period and one of said window periods that next precedes said each window period in said series; increasing rate calculating means connected to said average power calculating means for calculating for said each window period a rate of increase of the average power calculated for said each window period relative to the average power calculated for said next preceding window period to produce a control signal having a first and a second value when the rate of increase calculated for said each window period is greater and less than a preselected value, respectively; second means connected to said window processing means and said increasing rate calculating means for calculating a plurality of autocorrelation coefficients for a plurality of joining intervals, respectively, by the use of reference members and joint members, said joining intervals differing from one another by the equal spacing between two successive ones of said windowed samples and including a shortest and a longest joining interval which are decided in accordance with said shortest and said longest pitch periods, respectively, said reference members being those prescribed ones of said windowed samples which are successively distributed throughout a reference fraction of said each window period, said reference fraction being placed farther with respect to time from the leading and the trailing ends of said each window period when said control signal has said first and said second values, respectively, said joint members being those sets of windowed samples, the windowed samples of each set being equal in number to said prescribed samples, which are successively distributed throughout a plurality of joint fractions of said each window period, respectively, said joint fractions being displaced in said each window period from said reference fraction by said joining intervals, respectively, farther from the trailing and the leading ends of said each window period when said control signal has said first and said second values, respectively; and third means connected to said second means for producing a second of said second-group signals by finding a greatest value of the autocorrelation coefficients calculated for the respective joining intervals for said each window period and making said second signal represent those joining intervals as the pitch periods of the speech sound in the respective window periods for which the autocorrelation coefficients having the greatest values are calculated for the respective window periods. - View Dependent Claims (3, 4)
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2. A speech analyzer for analyzing an input speech sound signal representative of speech sound of an input speech sound waveform into a plurality of signals of a first group representative of a preselected one of spectral distribution information and spectral envelope information of said speech sound waveform and at least two signals of a second group representative of sound source information of said speech sound, said speech sound having a pitch period of a value variable between a shortest and a longest pitch period, said speech analyzer comprising:
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window processing means for processing said input speech sound signal into a sequence of a predetermined number of windowed samples, said sequence lasting each of a series of predetermined window periods, said windowed samples being representative of the speech sound in said each window period and equally spaced with respect to time between a leading and a trailing end of said each window period; first means connected to said window processing means for processing said windowed sample sequences into said first-group signals and a first of said second-group signals, said first signal being representative of amplitude information of the speech sound in the respective window periods; second means connected to said window processing means for simultaneously calculating two autocorrelation coefficient series, a first of said series consisting of a plurality of autocorrelation coefficients calculated for a plurality of joining intervals, respectively, by the use of reference members and joint members, said joining intervals differing from one another by the equal spacing between two successive ones of said windowed samples and including a shortest and a longest joining interval which are decided in accordance with said shortest and said longest pitch periods, respectively, said reference members being those prescribed ones of said windowed samples which are successively distributed throughout a first reference fraction of said each window period, said first reference fraction being placed farther with respect to time from the leading end of said each window period, said joint samples being those first sets of windowed samples, the windowed samples in each of said first sets being equal in number to said prescribed samples, which are successively distributed throughout a plurality of first joint fractions of said each window period, respectively, said first joint fractions being displaced in said each window period by said joining intervals, respectively, farther from the trailing end of said each window period, a second of said series consisting of a plurality of autocorrelation coefficients calculated for said joining intervals, respectively, by the use of reference members and joint members, the last-mentioned reference members being those prescribed ones of said windowed samples which are successively distributed throughout a second reference fraction of said each window period, said second reference fraction being placed farther with respect to time from the trailing end of said each window period, the last-mentioned joint members being those second sets of windowed samples, the windowed samples in each of said second sets being equal in number to the last-mentioned prescribed samples, which are successively distributed throughout a plurality of second joint fractions of said each window period, respectively, said second joint fractions being displaced in said each window period by said joining intervals, respectively, farther from the leading end of said each window period; comparing means connected to said second means for comparing the autocorrelation coefficients of said first series calculated for the respective joining intervals in said each window period with one another to select a first maximum autocorrelation coefficient for said each window period, the autocorrelation coefficients of said second series calculated for the respective joining intervals in said each window period with one another to select a second maximum autocorrelation coefficient for said each window period, and said first and said second maximum autocorrelation coefficients with each other to select the greater of the two and to find for said each window period a greatest value that said greater autocorrelation coefficient has, said comparing means thereby finding such greatest values for the respective window periods; and third means connected to said comparing means for producing a second of said second-group signals with said second signal made to represent those joining intervals as the pitch periods of the speech sound in the respective window periods for which the autocorrelation coefficients having said greatest values are calculated for the respective window periods.
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Specification