Abstract: An integrated circuit device or chip digitally synthesizes human speech employing a linear predictive filter and a variable frame rate. The variable frame rate provides a more natural speech by slowing or speeding the frame rate for a particular application used in a system which constructs the speech data to be synthesized from allophone codes.

Abstract: Method and apparatus for converting voice characteristics of synthesized speech from a single applied source of synthesized speech in a manner obtaining modified voice characteristics pertaining to the apparent age and/or sex of the speaker. The apparatus is capable of altering the voice characteristics of synthesized speech to obtain modified voice sounds simulating child-like, teenage, adult, aged and sexual preference characteristics by control of vocal track parameters including pitch period, vocal tract model, and speech data rate. A source of synthesized speech having a predetermined pitch period, a predetermined vocal tract model, and a predetermined speech rate is separated into the respective speech parameters. The values of pitch, the speech data frame length, and the speech data rate are then varied in a preselected manner to modify the voice characteristics of the synthesized speech from the source thereof.

Abstract: Speech synthesis system implementable in an integrated circuit device capable of converting frames of speech data at a variable frame rate into analog signals representative of human speech. The frames of speech data comprise digital representations of values of pitch, energy, filter coefficients and coded frame rate data. The speech synthesis system includes a linear predictive coding filter as a speech synthesizer which utilizes the speech data at a varying frame rate to produce digital speech signals representative of human speech. Frames of digital speech data including coded frame rate data are received by an input, with the frame rate data being decoded to control both the rate at which the incoming variable-length frames of speech data are accepted by the speech synthesizer and the number of interpolation calculations required to define interpolated speech values between adjacent incoming frames of speech data.

Abstract: A speech synthesis system with a linear predictive filter. The linear predictive filter utilizes coded reflection coefficients to produce digital signals representative of human speech. A variable interpolation circuit within the linear predictive filter allows a variable number of interpolation steps to be calculated between successive values of reflection coefficients. Additionally, a user programmable option allows the user to select a linear, nonlinear, or a combination form of interpolation based on stored scale data. The synthesizer output circuit also functions as a digital-to-analog converter.

Abstract: Integrated circuit speech synthesis system utilizing complementary metal-insulator-semiconductor technology to achieve low voltage operation, wherein a pluse width modulated digital-to-analog converter is employed to provide for accurate conversion of digital signals into analog signals even though the low voltage operation prohibits the large voltage swings normally required for digital-to-analog converter circuitry. The speech synthesis system includes a linear predictive filter as a speech synthesizer which utilizes coded reflection coefficients to produce digital signals representative of human speech. A microprocessor controls the access of digitized speech data which is stored in a memory. The speech synthesizer and microprocessor along with the pulse width modulated digital-to-analog converter are implemented in complementary metal-insulator-semiconductor technology.

Abstract: A speech synthesis system with a linear predictive filter. The linear predictive filter utilizes coded reflection coefficients to produce digital signals representative of human speech. A variable interpolation circuit within the linear predictive filter allows a variable number of interpolation steps to be calculated between successive values of reflection coefficients. Additionally, a user programmable option allows the user to select a linear, nonlinear, or a combination form of interpolation based on stored scale data.

Abstract: Speech parameter signals may be coded to consist of fewer bits for data reduction in memory. In this system both coded and uncoded signals are stored with an associated control signal which controls selection of corresponding direct or decoder circuit coupling of memory output to a speech synthesizer.

Abstract: A speech synthesis circuit implementable in an integrated circuit device, capable of converting frames of data into analog signals representative of human speech. The frames of data are comprised of digital representations of values of pitch, energy and certain filter coefficients, which are stored in non-volatile memory. The filter coefficients are utilized to control a linear predictive filter which is excited by voiced and unvoiced excitations stored in non-volatile memory. A control circuit coupling the excitation signals to the linear predictive filter allows the operator to select an external excitation signal rather than precalculated stored excitation signals. Thus, the synthesizer may be utilized in a vocoder application, wherein a residual excitation signal transmitted from an analysis circuit may be utilized as the excitation signal.

Abstract: A pulse width modulated digital-to-analog converter for utilization in low voltage, integrated circuit speech synthesis circuitry. A digitally programmable shift register is utilized to generate a pulse, which is generally related to the magnitude of a digital signal. A programmable delay circuit provides finer resolution by converting the least significant digital bits of data into pulse width information of shorter duration than the minimum pulse width generated by the controllable shift register. Pulse width information generated by the shift register and delay circuit is applied to the bases of two crossconnected transistors to drive a speaker or voice coil.