Voice synthesizer

Claim 2

In a voice synthesizer for phoneticly synthesizing human speech: a vocal tract model comprising tunable filters and amplitude control devices responsive to input signal quantities to determine the frequency and amplitude parameters of phonemes to be output therefrom; input means for specifying selected phonemes to be output from said vocal tract model and said parameters thereof in a predetermined order; and control signal forming means connected between said input means and said tunable filters and amplitude control devices of the vocal tract model for producing a plurality of variable duty cycle waveforms as input signals for controlling the frequency and amplitude characteristics of the selected phonemes.

Claim 3

Apparatus as defined in claim 1 wherein said input means comprises means for specifying a phoneme code having a plurality of bits, said signal forming means between the input means and vocal tract model including means for cyclically outputting said bits in series according to a predetermined timing sequence having a numerically progressive order whereby said bits define said duty cycle waveforms, the average value of which varies according to the selected bits of said code.

Claim 4

Apparatus as defined in claim 1 wherein said signal forming means comprises filter means for producing a dc signal related to the average value of the duty cycle waveforms.

Claim 5

Apparatus as defined in claim 3 further including means for converting said dc signal to a second variable duty cycle signal of fixed frequency and amplitude for application to said vocal tract model.

Claim 6

Apparatus as defined in claim 1 including buffer means connected in said signal forming means for establishing precision voltage levels for said variable duty cycle signals.

Claim 7

Apparatus as defined in claim 1 wherein said input means includes timing control means for selecting a relative time interval for each specified phoneme, and timing control means for varying the overall rate of phonetic production while preserving the relative timing between said phonemes.

Claim 8

Apparatus as defined in claim 6 wherein said signal forming means comprises filter means for producing a dc signal related to the average value of the duty cycle waveforms.

Claim 9

Apparatus as defined in claim 7 wherein said filter has a response time which is slow relative to the phoneme repetition rate.

Claim 10

Apparatus as defined in claim 8 wherein said timing control means includes means for varying the response time of said filter to track with said overall rate of phonetic production.

Claim 11

Apparatus as defined in claim 1 wherein said signal forming means comprises at least one storage facility having input address means and output control means some but not all of the input means being connected to receive phoneme address signals, said facility having stored therein a plurality of phoneme control parameters which are applied to said output means according to thE address signals, each phoneme address signal combination applied to said some of the input means being effective to select a plurality of parameter control signals for application to an output, timing signal means connected to the remaining input means for applying thereto timing signals for applying the selected control signals to the output individually and in a sequence having a binary-weighted time order such that the average value of the total sequence is a function of the particular address signal combination.

Claim 12

Apparatus as defined in claim 10 wherein the sequence timing is in the order 8-4-2-1 such that the average value may occur in the range of 0 to 15.

Claim 13

Apparatus as defined in claim 10 wherein the control signals on said output comprise an electrical wave-form which varies between two relatively fixed amplitude levels.

Claim 14

Apparatus as defined in claim 12 further including buffer means connected to receive the control signal sequence for reproducing said sequence but with a close-tolerance on said amplitude levels.

Claim 15

Apparatus as defined in claim 13 including a filter connected to receive the control signal sequence and to output a dc signal related to the average value thereof, the filter having a response time which is slow relative to the rate at which the average value varies from one selected value to another.

Claim 16

Apparatus as defined in claim 14 further including timing means for controlling the rate of phoneme selection, said means being connected to the filter for varying said response time to track with the rate selected.

Claim 17

Apparatus as defined in claim 15 wherein the filter comprises gate means connected to transmit the parameter signal value, and a control terminal connected to receive a high frequency signal having a variable duty cycle thereby to control the ON-time of the gate means.

Claim 18

Apparatus as defined in claim 16 further including means connected to said filter for converting the dc signal to a variable duty cycle signal for application to the vocal model.

Claim 19

Apparatus as defined in claim 1 including as part of said vocal tract model a source of voiced phonetic excitation quantity and a source of unvoiced phonetic excitation quantity, and means responsive to the addressing of a consecutive phonetic sequence of voiced and unvoiced phonetic quantities for producing a predetermined delay in the excitation of at least one of said quantities.