Formant vocoder utilizing resonator damping

Claim 2

In a system for reproducing a signal representative of a speech wave, a speech synthesizer comprising: a plurality of resonator circuits, at least one of said resonator circuits comprising amplifier means, the bandwidth of said one of said resonator circuits being dependent on the gain of said amplifier means; first means coupled to each of said plurality of resonator circuits for regulating the resonant frequency of said resonator circuits; second means coupled to each of said plurality of resonator circuits for supplying ringing energy to said resonator circuits upon the occurrence of each of a succession of pulses respectively representative of successive pitch pulses of said speech wave; and damping means coupled to said one of said resonator circuits, for controlling the bandwidth of said one resonator circuit, the improvement wherein said damping means comprises: third means for controlling the gain of said amplifier means, said third means being responsive to a control signal to exhibit between a pair of terminals of said third means a first resistance when said control signal has a first value and a second resistance when said control signal has a second has a second value, means coupling said pair of terminals of said third means to said amplifier means, said amplifier having a first gain when said third means exhibits said first resistance between said pair of terminals and having a second gain lower than said first gain when third means exhibits said second resistance between said pair of terminals, a differential amplifier for supplying to said third means, in response to an input signal of given magnitude, a control signal having said first value, and for supplying to said third means, in response to an input signal of another magnitude different from said given magnitude, a control signal having said second value, and means for supplying to said differential amplifier an input signal having said other magnitude at a first time following the occurrence of the pulse representative of one of said pitch pulses and changing to said given magnitude at a second time before the occurrence of the pulse representative of the succeeding one of said pitch pulses, whereby said bandwidth of said one resonator circuit is widened between said wave: time and said second time.

Claim 3

In a system for reproducing a signAl representative of a speech wave: a speech analyzer comprising first means for producing in response to said speech wave signals representative of the frequencies and amplitudes of a plurality of formants of said speech wave, and second means for producing in response to said speech wave signals representative of the pitch rate of said speech wave; a speech synthesizer comprising oscillator means responsive to said signals produced by said second means to generate a succession of voltage pulses at said pitch rate, a plurality of modulators, third means for coupling said modulators in parallel to said oscillators means, fourth means for supplying each of said signals respectively representative of the amplitudes of said plurality of formants of said speech wave to a different one of said modulators, a plurality of resonator circuits each having first and second input terminals, at least one of said resonator circuits having amplifier means, the bandwidth of said one of said resonator circuits being dependent on the gain of said amplifier means, each of said plurality of resonator circuits having said first input terminal thereof coupled to a different one of said modulators, fifth means for supplying each of said plurality of signals respectively representative of the frequencies of said formants to said second input terminal of a different one of said resonator circuits, and damping means coupled to said one of said resonator circuits, for controlling the bandwidth of said one resonator circuit, the improvement wherein said damping means comprises: sixth means for controlling the gain of said amplifier means, said sixth means being responsive to a control signal to exhibit between a pair of terminals of said sixth means a first resistance when said control signal has a first value and a second resistance when said control signal has a second value, means coupling said pair of terminals of said sixth means to said amplifier means, said amplifier means having a first gain when said sixth means exhibits said first resistance between said pair of terminals and having a second gain lower than said first gain when said sixth means exhibits said second resistance between said pair of terminals, a differential amplifier for supplying to said sixth means, in response to an input signal of given magnitude, a control signal having said first value, and for supplying to said sixth means, in response to an input signal of another magnitude different from said given magnitude, a control signal having said second value, and means for supplying to said differential amplifier an input signal having said other magnitude at a first time following the occurrence of one of said voltage pulses and changing to said given magnitude at a second time before the occurrence of a succeeding one of said voltage pulses, whereby said bandwidth of said one resonator circuit is widened between said first time and said second time.

Claim 4

In a system for reproducing a signAl representative of a speech wave: a speech analyzer comprising first means for producing in response to said speech wave signals representative of the frequencies and amplitudes of a plurality of formants of said speech wave, and second means for producing in response to said speech wave signals representative of the pitch rate of said speech wave; a speech synthesizer comprising oscillator means responsive to said signals produced by said second means to generate a succession of voltage pulses at said pitch rate, a plurality of modulators, third means for coupling said modulators in parallel to said oscillators means, fourth means for supplying each of said signals respectively representative of the amplitudes of said plurality of formants of said speech wave to a different one of said modulators, a plurality of resonator circuits each having first and second input terminals, at least one of said resonator circuits having amplifier means, the bandwidth of said one of said resonator circuits being dependent on the gain of said amplifier means, each of said plurality of resonator circuits having said first input terminal thereof coupled to a different one of said modulators, fifth means for supplying each of said plurality of signals respectively representative of the frequencies of said formants to said second input terminal of a different one of said resonator circuits, and damping means coupled to said one of said resonator circuits, for controlling the bandwidth of said one resonator circuit, the improvement wherein said damping means comprises: sixth means for controlling the gain of said amplifier means, said sixth means being responsive to a control signal to exhibit between a pair of terminals of said sixth means a first resistance when said control signal has a first value and a second resistance when said control signal has a second value, means coupling said pair of terminals of said sixth means to said amplifier means, said amplifier means having a first gain when said sixth means exhibits said first resistance between said pair of terminals and having a second gain lower than said first gain when said sixth means exhibits said second resistance between said pair of terminals, a differential amplifier for supplying to said sixth means, in response to an input signal of given magnitude, a control signal having said first value, and for supplying to said sixth means, in response to an input signal of another magnitude different from said given magnitude, a control signal having said second value, and means for supplying to said differential amplifier an input signal having said other magnitude at a first time following the occurrence of one of said voltage pulses and changing to said given magnitude at a second time before the occurrence of a succeeding one of said voltage pulses, whereby said bandwidth of said one resonator circuit is widened between said first time and said second time.

Claim 5

The system of claim 2 wherein said analyzer includes means for producing a voicing signal, said synthesizer includes a noise generator, and said third means includes a gating circuit controlled by said voicing signal and coupled to said oscillator means and said noise generator so that, depending upon the amplitude of the voicing signal, either the output signal of said noise generator or the output signal of said oscillator means is coupled to said modulators.