Formant-based speech synthesizer
First Claim
1. A formant-based speech synthesizer comprising:
- glottal signal path including, in series, glottal filter means for shaping glottal signal path input signals, at least a first, second and third formant filter means for augmenting individual formant frequencies, and glottal path attenuating means for providing a variably attenuated glottal output signal;
fricative signal path including, in series, modulating means for modulating fricative signal path input signals, fricative path attenuating means for variably attenuating fricative signal path signals and a PZ filter means for augmenting pole and zero frequencies;
pitch means for generating a glottal source signal;
pseudorandom noise means for generating a fricative source signal;
first switch means for selectively connecting said pitch means or said noise means to said glottal signal path as an input signal;
second switch means for selectively disconnecting said PZ filter means from said fricative signal path and connecting said PZ filter means between said formant filter means and said glottal path attenuating means;
third switch means for selectively disconnecting said formant filter means from said glottal signal path and connecting said glottal filter means to said glottal path attenuating means;
rectifier means connected to the output of said first fromant filter means for half-wave rectifying the filtered first formant signal;
fourth switch means for selectively connecting said rectifier means or a fixed amplitude signal to said modulating means; and
output means for selectively providing an output signal from said glottal signal path, said fricative signal path or from both signal paths in combination.
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Abstract
A formant-based multi-path speech synthesizer is reconfigurable to use common elements for different types of sounds. A pitch generator or a noise generator is connected to a glottal signal path for vowel or aspirate sound, respectively. The pole and zero filters normally part of the fricative signal path which produces fricative or stop sounds are used in the glottal signal path for nasal sounds. The output of a spectral filter in the glottal signal path bypasses the cascaded formant filters and is connected directly to the glottal path attenuator for voice bar sounds. The output of the first formant filter is rectified and modulates the noise signal in the fricative path and the glottal and fricative signal paths are summed for voiced fricative sounds. To minimize spectral tilt, the third and fourth formant filters and the pole filter are peak filters. The glottal path attenuator is at the end of the glottal signal path to maximize the signal-to-noise ratio.
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Citations
22 Claims
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1. A formant-based speech synthesizer comprising:
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glottal signal path including, in series, glottal filter means for shaping glottal signal path input signals, at least a first, second and third formant filter means for augmenting individual formant frequencies, and glottal path attenuating means for providing a variably attenuated glottal output signal; fricative signal path including, in series, modulating means for modulating fricative signal path input signals, fricative path attenuating means for variably attenuating fricative signal path signals and a PZ filter means for augmenting pole and zero frequencies; pitch means for generating a glottal source signal; pseudorandom noise means for generating a fricative source signal; first switch means for selectively connecting said pitch means or said noise means to said glottal signal path as an input signal; second switch means for selectively disconnecting said PZ filter means from said fricative signal path and connecting said PZ filter means between said formant filter means and said glottal path attenuating means; third switch means for selectively disconnecting said formant filter means from said glottal signal path and connecting said glottal filter means to said glottal path attenuating means; rectifier means connected to the output of said first fromant filter means for half-wave rectifying the filtered first formant signal; fourth switch means for selectively connecting said rectifier means or a fixed amplitude signal to said modulating means; and output means for selectively providing an output signal from said glottal signal path, said fricative signal path or from both signal paths in combination. - View Dependent Claims (2, 3, 4, 5, 6)
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7. In a formant-based speech synthesizer having a glottal signal generation path and a fricative signal generation path, the improvement being said glottal signal generation path which comprises in series:
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glottal source means for providing a glottal source signal; glottal filter means for spectral shaping said glottal source signal; first formant second order lowpass filter; second formant second order lowpass filter; third formant second order peak filter; a fourth formant second order peak filter; and glottal path attenuating means for providing an attenuated glottal output signal. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A formant-based speech synthesizer reconfigurable to produce vowels, aspirates, nasals, voice bar, fricatives, stops and voiced fricative sounds comprising:
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glottal signal path including, in-series, glottal filter means for shaping glottal signal path input signals, at least a first, second and third formant filter means for augmenting individual formant frequencies, and glottal path attenuating means for providing an attenuated glottal output signal; fricative signal path including, in series, modulating means for modulating fricative signal path input signals, fricative path attenuating means for attenuating fricative signal path signals and a PZ filter means for augmenting pole and zero frequencies; pitch means for generating a glottal source signal; pseudorandom noise means for generating a fricative source signal; configuration control means for (a) connecting said pitch means to said glottal signal path to produce vowel sounds, (b) connecting said noise means to said glottal signal path to produce aspirate sounds, (c) disconnecting said PZ filter means from said fricative signal path and connecting said PZ filter means between said formant filter means and said glottal path attenuating means to produce nasal sounds, (d) connecting said glottal filter means directly to said glottal path attenuating means bypassing said formant filter means to produce voice bar sounds, (e) connecting said noise means to said modulator means and a fixed amplitude signal to said modulator means for fricative and stop sounds, and (f) connecting said pitch means to said glottal signal path, said noise means to said fricative path, a portion of the output of said first formant filter means to said modulator means and summing the output of said glottal and fricative signal paths to produce voiced fricative sounds. - View Dependent Claims (15, 16, 17, 18, 19)
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20. A formant-based speech synthesizer comprising:
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glottal signal path including, in series, glottal filter means for shaping glottal signal path input signals, at least a first, second and third formant filter means for augmenting individual formant frequencies, and glottal path attenuating means for providing a variably attenuated glottal output signal; fricative signal path including, in series, fricative path attenuating means for variably attenuating fricative signal path signals and a PZ filter means for augmenting pole and zero frequencies; pitch means for generating a glottal source signal; pseudorandom noise means for generating a fricative source signal; first switch means for selectively connecting said pitch means or said noise means to said glottal signal path as an input signal; second switch means for selectively disconnecting said PZ filter means from said fricative signal path and connecting said PZ filter means between said formant filter means and said glottal path attenuating means; and output means for selectively providing an output signal from said glottal signal path, said fricative signal path or from both signal paths in combination. - View Dependent Claims (21, 22)
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Specification