Voice synthesizer with automatic pitch and speech rate modulation

• US 4,470,150 A
• Filed: 03/18/1982
• Issued: 09/04/1984
• Est. Priority Date: 03/18/1982
• Status: Expired due to Fees

• Current Assignee: Federal Screw Works
• Original Assignee: Federal Screw Works
• Inventors: Ostrowski, Carl L.
• Primary Examiner(s): Kemeny, E. S. Matt
• Application Number:
  US06/359,595
• Time in Patent Office: 901 Days
• Field of Search: 381/51-53, 381/36-40, 364/513.5
• US Class Current: 704/261
• CPC Class Codes: G10L 13/10 Prosody rules derived from text; Stress or intonation

Abstract

Understandability of synthesized speech is improved by random modulation: after a predetermined number of phonemes, the speech rate is changed by a random amount, with proportional changes in pitch and phoneme transition rate.

Claims

1. An improved electronic voice synthesizer of the type having

input circuit means responsive to input data identifying a sequence of phonemes for generating control and excitation signals that electronically define each phoneme in the sequence;

and

vocal tract circuit means responsive to said control and excitation signals for substantially producing the frequency spectrum of each phoneme in the sequence;

wherein the improvement comprises;

means for automatically varying the pitch and timing of the phonemes independently of the input data to produce variations in the pitch and rate of the synthesized speech, wherein a change in the pitch of a given phoneme is accomplished by an inversely proportional change in the timing of that phoneme.

2. An improved electronic device for phonetically synthesizing human speech as recited in claim 1, wherein the automatic variations in pitch and timing of the phonemes are substantially random.

3. An improved electronic voice synthesizer of the type having

input circuit means responsive to input data identifying a sequence of phonemes for generating control and excitation signals that electronically define each phoneme in the sequence, including variable rate transition circuits for smoothing the abrupt amplitude variations in at least some of said control signals which may occur during the transition from any given phoneme to the next phoneme in the sequence;

and

vocal tract circuit means responsive to said control and excitation signals from the input circuit means for substantially producing the frequency spectrum of each phoneme in the sequence;

wherein the improvement comprises;

means for automatically varying the timing of the phonemes independently of the input data to produce variations in the rate of the synthesized speech; and

means for varying the transition rates of the transition circuits in proportion to the variations in the rate of the synthesized speech.

4. An improved electronic voice synthesizer as recited in claim 3, wherein the automatic variations in the timing of the phonemes are substantially random.

5. An improved electronic device for phonetically synthesizing human speech of the type having

input circuit means responsive to input data identifying a sequence of phonemes for generating control and excitation signals that electronically define each phoneme in the sequence, including an inflection control signal for controlling the inflection level of the synthesized speech and a timing control signal for establishing a basic period of production for each phoneme;

and

vocal tract means responsive to said control and excitation signals for substantially producing the frequency spectrum of each phoneme in the sequence;

wherein the improvement comprises;

a pitch and speech rate modulation circuit adapted to automatically vary the pitch and rate of the synthesized speech wherein a change in the pitch of a given phoneme is accompanied by an inversely proportional change in the timing of that phoneme, including a random generator circuit adapted to produce a modulation signal and automatically alter the value of said modulation signal to a new random value after a number of phonemes have been synthesized, first circuit means for altering said inflection control signal in proportion to the value of said modulation signal, and second circuit means for altering said timing control signal so the basic period of production for each phoneme varies in inverse proportion to the value of said modulation signal.

8. An improved electronic device for phonetically synthesizing human speech as recited in claim 5, 6 or 7, wherein the random generator circuit comprises:

a counter that produces an output after a number of phonemes have been synthesized; and

a random generator that produces the modulation signal and automatically alters the value of said modulation signal to a new random value whenever said counter produces an output.

6. An improved electronic device for phonetically synthesizing human speech of the type having

input circuit means responsive to input data identifying a sequence of phonemes for generating control and excitation signals that electronically define each phoneme in the sequence, including a timing control signal for establishing a basic period of production for each phoneme;

and

vocal tract circuit means responsive to said control and excitation signals for substantially producing the frequency sprectrum of each phoneme in the sequence;

wherein the improvement comprises;

speech rate modulation means for automatically varying the timing of the phonemes independently of the input data, including a random generator circuit adapted to produce a modulation signal and automatically alter the value of said modulation signal to a new random value after a number of phonemes have been synthesized, and circuit means for altering the timing control signal so the basic period of production for each phoneme varies in accordance with the value of said modulation signal.

7. An improved electronic device for phonetically synthesizing human speech of the type having

input circuit means responsive to input data identifying a sequence of phonemes for generating control and excitation signals that electronically define each phoneme in the sequence, including an inflection control signal for controlling the inflection level of the synthesized speech;

and

vocal tract circuit means responsive to said control and excitation signals for substantially producing the frequency spectrum of each phoneme in the sequence;

wherein the improvement comprises;

pitch modulation means for automatically varying the pitch of the phonemes independently of the input data, including a random generator circuit adapted to produce a modulation signal and automatically alter the value of said modulation signal to a new random value after a member of phonemes have been synthesized, and circuit means for altering the value of the inflection control signal in accordance with the value of said modulation signal.

9. An improved electronic device for phonetically synthesizing human speech, comprising:

input circuit means responsive to input data identifying a sequence of phonemes for generating control and excitation signals that electronically define each phoneme in the sequence, including variable rate transition circuits for smoothing out abrupt amplitude variations in some control signals which may occur during the transition from any given phoneme to the next phoneme in the sequence, and a control signal storage circuit provided with tri-state outputs connected to the variable rate transition circuits, said outputs being adapted to intermittently assume an open-circuit state;

vocal tract circuit means responsive to said control and excitation signals from the input circuit means for substantially producing the frequency spectrum of each phoneme in the sequence;

means for automatically varying the timing of the phonemes independently of the input data to produce variations in the rate of the synthesized speech; and

means for varying the transition rates of the transition circuits in proportion to the variations in the rate of synthesized speech by altering the periods of time during which the tri-state outputs of the storage circuit are in an open-circuit state,

thereby making the transition rates of the transition circuits correspond more precisely to the varying rate of the synthesized speech.

10. A method for modulating the pitch of phonetically synthesized speech, comprising:

sequentially generating a series of random values within a preselected range of values;

holding each value generated in the series while a number of phonemes are synthesized before generating the next value in the series of random values; and

altering the normal pitch of each phoneme synthesized in accordance with the magnitude of the random value then held.

11. A method of modulating the speech rate of phonetically synthesized speech, comprising:

sequentially generating a series of random values within a preselected range of values;

holding each value generated in the series while a number of phonemes are synthesized before generating the next value in the series of random values; and

altering the basic period of production of each phoneme synthesized in accordance with the magnitude of the random value then held.

12. A method for modulating the pitch and speech rate of phonetically synthesized speech, comprising:

sequentially generating a series of random values within a preselected range of values;

holding each value generated in the series while a number of phonemes are synthesized before generating the next value in the series of random values;

altering the normal pitch of each phoneme synthesized in proportion to the magnitude of the random value then held; and

altering the basic period of production of each phoneme synthesized in inverse proportion to the magnitude of the random value then held.