Helium environment vocoder

Claim 2

A helium environment vocoder having a multichannel speech analyzer, a multichannel speech synthesizer and an excitation system for extracting time varying characteristics of the excitation function of input helium speech and reproducing this function for the excitation of said synthesizer, said excitation system comprising: first means coupled to said analyzer for extracting continuously the fundamental frequency from said input speech; second means coupled to said first means for producing a sequence of pulses at a rate having predetermined relationship to said fundamental frequency; a noise generator to produce noise; third means coupled to said analyzer for determining whether said input speech is voiced or unvoiced; fourth means coupled to said second means, said noise generator and said third means responsive to the output signal of said third means for selecting said sequence of pulses if said input speech is voiced and for selecting said noise from said noise generator if said input speech is unvoiced; and fifth means coupled to said fourth means and said synthesizer for applying the selected one of said sequence of pulses and said noise as an excitation input pulse stream to said synthesizer, said input pulse stream having a constant energy level; said third means including a comparator having two inputs and an output, one of said inputs being coupled to a first group of channels of said analyzer having a passband related to voiced speech and the other of said inputs being coupled to a second group of channels of said analyzer having a passband related to unvoiced speech, said second group of channels being different than said first group of channels, and a two level clamp circuit coupled to said other of said two inputs to hold said output in one condition when the input exceeds a predetermined first threshold level and to hold said output in the other condition when that input falls below a second predetermined threshold level lower than said first threshold level.

Claim 3

A helium enviornment vocoder having a multichannel speech analyzer, a multichannel speech synthesizer and an excitation system for extracting time varying characteristics of the excitation function of input helium speech and reproducing this function for the excitation of said synthesizer, said excitation system comprising: first means coupled to said analyzer for extracting continuously the fundamental frequency from said input speech; second means coupled to said first means for producing a sequence of pulses at a rate having a predetermined relationship to said fundamental frequency; a noise generator to produce noise; third means coupled to said analyzer for determining whether said input speech is voiced or unvoiced; fourth means coupled to said second means, said noise generator and said third means responsive to the output signal of said third means for selecting said sequence of pulses if said input speech is voiced and for selecting said noise from said noise generator if said input speech is unvoiced; and fifth means coupled to said fourth means and said synthesizer for applying the selected one of said sequence of pulses and said noise as an excitation input pulse stream to said synthesizer, said input pulse stream having a constant energy level; said second means including a voltage controlled multivibrator, and an input circuit for said multivibrator having a capacitor, and a pair of isolating diodes coupled to said capacitor, said pair of diodes having coupled thereto for applying to said capacitor through said pair of diodes a direct current voltage bearing a predetermined relationship to said fundamental frequency.

Claim 4

A helium enviornment vocoder having a multichannel speech analyzer, a multichannel speech synthesizer and an excitation system for extracting time varying characteristics of the excitation function of input helium speech and reproducing this function for the excitation of said synthesizer, said excitation system comprising: first means coupled to said analyzer for extracting continuously the fundamental frequency from said input speech; second means coupled to said first means for producing a sequence of pulses at a rate having a predetermined relationship to said fundamental frequency; a noise generator to produce noise; third means coupled to said analyzer for determining whether said input speech is voiced or unvoiced; fourth means coupled to said second means, said noise generator and said third means responsive to the output signal of said third means for selecting said sequence of pulses if said input speech is voiced and for selecting said noise from said noise generator if said input speech is unvoiced; and fifth means coupled to said fourth means and said synthesizer for applying the selected one of said sequence of pulses and said noise as an excitation input pulse stream to said synthesizer, said input pulse stream having a constant energy level; said second means including a voltage controlled multivibrator, and an input circuit for said multivibrator having a capacitor, and a pair of isolating diodes coupled to said capacitor, said pair of diodes having coupled thereto for applying to said capacitor through said pair of diodes a direct current voltage bearing a predetermined relationship to said fundamental frequency.

Claim 5

A vocoder according to claim 2, wherein said third means includes a comparator having two inputs and an output, one of said inputs being coupled to a first group of channels of said analyzer having a passband related to voiced speech and the other of said inputs being coupled to a second group of channels of said analyzer having a passband related to unvoiced speech, said second group of channels being different than said first group of channels, and a two level clamp circuit coupled to one of said two inputs to hold said output in one condition when the input exceeds a predetermined first threshold level and to hold said output in the other condition when that input falls below a second predetermined threshold level lower than said first threshold level.

Claim 6

A helium enviornment vocoder having a multichannel speech analyzer, a multichannel speech synthesizer and an excitation system for extracting time varying characteristics of the excitation function of input helium speech and reproducing this function for the excitation of said synthesizer, said excitation system comprising: first means coupled to said analyzer for extracting continuously the fundamental frequency from said input speech; second means coupled to said first means for producing a sequence of pulses at a rate having a predetermined relationship to said fundamental frequency; a noise generator to produce noise; third means coupled to said analyzer for determining whether said input speech is voiced or unvoiced; fourth means coupled to said second means, said noise generator and Said third means responsive to the output signal of said third means for selecting said sequence of pulses if said input speech is voiced and for selecting said noise from said noise generator if said input speech is unvoiced; and fifth means coupled to said fourth means and said synthesizer for applying the selected one of said sequence of pulses and said noise as an excitation input pulse stream to said synthesizer, said input pulse stream having a constant energy level; each channel of said analyzer including a bandpass filter coupled to said input speech signal, the passband of said bandpass filter being different for each channel, and a rectifier coupled to the output of said bandpass filter; and said first means including sixth means coupled in parallel to the output of a given number of said rectifiers to produce a sum of the output signals passed by each of said given number of said rectifiers, a first differential amplifier having an output and two inputs, one of said two inputs of said first differential amplifier being coupled to said sixth means to receive said sum of said ouput signals, a seventh means coupled between said sixth means and the other of said two inputs of said first differential amplifier to smooth said sum of said output signals prior to being applied to said other of said two inputs of said first differential amplifier, eighth means coupled to said output of said first differential amplifier to square the output signal of said first differential amplifier, a monostable circuit coupled to said eighth means driven by a squared output signal from said eighth means, and a low pass filter means having gain coupled to the output of said monostable circuit to operate on the output signal of said monostable circuit.

Claim 7

A helium enviornment vocoder having a multichannel speech analyzer, a multichannel speech synthesizer and an excitation system for extracting time varying characteristics of the excitation function of input helium speech and reproducing this function for the excitation of said synthesizer, said excitation system comprising: first means coupled to said analyzer for extracting continuously the fundamental frequency from said input speech; second means coupled to said first means for producing a sequence of pulses at a rate having a predetermined relationship to said fundamental frequency; a noise generator to produce noise; third means coupled to said analyzer for determining whether said input speech is voiced or unvoiced; fourth means coupled to said second means, said noise generator and Said third means responsive to the output signal of said third means for selecting said sequence of pulses if said input speech is voiced and for selecting said noise from said noise generator if said input speech is unvoiced; and fifth means coupled to said fourth means and said synthesizer for applying the selected one of said sequence of pulses and said noise as an excitation input pulse stream to said synthesizer, said input pulse stream having a constant energy level; each channel of said analyzer including a bandpass filter coupled to said input speech signal, the passband of said bandpass filter being different for each channel, and a rectifier coupled to the output of said bandpass filter; and said first means including sixth means coupled in parallel to the output of a given number of said rectifiers to produce a sum of the output signals passed by each of said given number of said rectifiers, a first differential amplifier having an output and two inputs, one of said two inputs of said first differential amplifier being coupled to said sixth means to receive said sum of said ouput signals, a seventh means coupled between said sixth means and the other of said two inputs of said first differential amplifier to smooth said sum of said output signals prior to being applied to said other of said two inputs of said first differential amplifier, eighth means coupled to said output of said first differential amplifier to square the output signal of said first differential amplifier, a monostable circuit coupled to said eighth means driven by a squared output signal from said eighth means, and a low pass filter means having gain coupled to the output of said monostable circuit to operate on the output signal of said monostable circuit.

Claim 8

A vocoder according to claim 4, wherein said third means includes a comparator having two inputs and an output, one of said inputs being coupled to a first group of channels of said analyzer having a passband related to voiced speech and the other of said inputs being coupled to a second group of channels of said analyzer having a passband related to unvoiced speech, said second group of channels being different than said first group of channels, and a two level clamp circuit coupled to one of said two inputs to hold said output in one condition when the input exceeds a predetermined first threshold level and to hold said output in the other condition when that input falls below a second predetermined threshold level lower than said first threshold level.

Claim 9

A vocoder according to claim 4, wherein said second means includes a voltage controlled multivibrator, and an input circuit for said multivibrator having a capacitor, and a pair of isolating diodes coupled to said capacitor, said pair of diodes having coupled thereto for applying to said capacitor through said pair of diodes a direct current voltage bearing a predetermined relationship to said fundamental frequency.

Claim 10

A vocoder according to claim 6, wherein said third means includes a comparator having two inputs and an output, one of said inputs being coupled to a first group of channels of said analyzer having a passband related to voiced speech and the other of said inputs being coupled to a second group of channels of said analyzer having a passband related to unvoiced speech, said second group of channels being different than said first group of channels, and a two level clamp circuit coupled to one of said two inputs to hold said output in one condition when the input exceeds a predetermined first threshold level and to hold said output in the other condition when that input falls below a second predetermined threshold level lower than said first threshold level.

Claim 11

A vocoder according to claim 4, wherein said eighth means includes a second differential amplifier having an output and two inputs, a first integrating network coupled between saiD output of said first differential amplifier and one of said two inputs of said second differential amplifier, and first integrating network having a first time constant, a second integrating network coupled between said output of said first differential amplifier and the other of said two inputs of said second differential amplifier, said second integrating network having a second time constant different than said first time constant, and a feedback network coupled between said output of said second differential amplifier and one of said two inputs of said second differential amplifier, said feedback network providing direct current negative feedback and no alternating current feedback.

Claim 12

A vocoder according to claim 8, wherein said third means includes a comparator having two inputs and an output, one of said inputs being coupled to a first group of channels of said analyzer having a passband related to voiced speech and the other of said inputs being coupled to a second group of channels of said analyzer having a passband related to unvoiced speech, said second group of channels being different than said first group of channels, and a two level clamp circuit coupled to one of said two inputs to hold said output in one condition when the input exceeds a predetermined first threshold level and to hold said output in the other condition when that input falls below a second predetermined threshold level lower than said first threshold level.

Claim 13

A vocoder according to claim 8, wherein said second means includes a voltage controlled multivibrator, and an input circuit for said multivibrator having a capacitor, and a pair of isolating diodes coupled to said capacitor, said pair of diodes having coupled thereto for applying to said capacitor through said pair of diodes a direct current voltage bearing a predetermined relationship to said fundamental frequency.

Claim 14

A vocoder according to claim 10, wherein said third means includes a comparator having two inputs and an output, one of said inputs being coupled to a first group of channels of said analyzer having a passband related to voiced speech and the other of said inputs being coupled to a second group of channels of said analyzer having a passband related to unvoiced speech, said second group of channels being different than said first group of channels, and a two level clamp circuit coupled to one of said two inputs to hold said output in one condition when the input exceeds a predetermined first threshold level and to hold said output in the other condition when that input falls below a second predetermined threshold level lower than said first threshold level.

Claim 15

A vocoder according to claim 10, further including switching means coupled to said second means, said third means and said input circuit for said multivibrator, said switching means being responsive to the detection of unvoiced speech by said third means to disconnect said second means from said input circuit for said multivibrator.

Claim 16

A vocoder according to claim 12, wherein said third means includes a comparator having two inputs and an output, one of said inputs being coupled to a first group of channels of said analyzer having a passband related to voiced speech and the other of said inputs being coupled to a second group of channels of said analyzer having a passband related to unvoiced speech, said second group of channels being different than said first group of channels, and a two level clamp circuit coupled to one of said two inputs to hold said output in one condition when the input exceeds a predetermined first threshold level and to hold said output in the other condition when that input falls below a second predetermined threshold level lower than said first threshold level.