Abstract: A technique, suitable for real-time processing, is disclosed for pitch tracking by detection of glottal excitation epochs in speech signal. It uses Hilbert envelope to enhance saliency of the glottal excitation epochs and to reduce the ripples due to the vocal tract filter. The processing comprises the steps of dynamic range compression, calculation of the Hilbert envelope, and epoch marking. The Hilbert envelope is calculated using the output of a FIR filter based Hilbert transformer and the delay-compensated signal. The epoch marking uses a dynamic peak detector with fast rise and slow fall and nonlinear smoothing to further enhance the saliency of the epochs, followed by a differentiator or a Teager energy operator, and amplitude-duration thresholding. The technique is meant for use in speech codecs, voice conversion, speech and speaker recognition, diagnosis of voice disorders, speech training aids, and other applications involving pitch estimation.

Abstract: Hearing aids for persons with sensorineural hearing loss aim to compensate for degraded speech perception caused by frequency-dependent elevation of hearing thresholds, reduced dynamic range, abnormal loudness growth, and increased temporal and spectral masking. A digital hearing aid is implemented as a smartphone application as an alternative to ASIC-based hearing aids. The implementation provides user-configurable processing for background noise suppression and dynamic range compression. Both processing blocks are implemented for real-time processing using single FFT-based analysis-synthesis. A touch-controlled graphical user interface enables the user to set and fine-tune the processing parameters in an interactive and real-time mode.

Abstract: Hearing aids for persons with sensorineural hearing loss aim to compensate for degraded speech perception caused by frequency-dependent elevation of hearing thresholds, reduced dynamic range, abnormal loudness growth, and increased temporal and spectral masking. A digital hearing aid is implemented as a smartphone application as an alternative to ASIC-based hearing aids. The implementation provides user-configurable processing for background noise suppression and dynamic range compression. Both processing blocks are implemented for real-time processing using single FFT-based analysis-synthesis. A touch-controlled graphical user interface enables the user to set and fine-tune the processing parameters in an interactive and real-time mode.

Abstract: A technique, suitable for real-time processing, is disclosed for pitch tracking by detection of glottal excitation epochs in speech signal. It uses Hilbert envelope to enhance saliency of the glottal excitation epochs and to reduce the ripples due to the vocal tract filter. The processing comprises the steps of dynamic range compression, calculation of the Hilbert envelope, and epoch marking. The Hilbert envelope is calculated using the output of a FIR filter based Hilbert transformer and the delay-compensated signal. The epoch marking uses a dynamic peak detector with fast rise and slow fall and nonlinear smoothing to further enhance the saliency of the epochs, followed by a differentiator or a Teager energy operator, and amplitude-duration thresholding. The technique is meant for use in speech codecs, voice conversion, speech and speaker recognition, diagnosis of voice disorders, speech training aids, and other applications involving pitch estimation.

Abstract: A circuit for realizing a precision and linear floating resistor, using MOSFET devices, is disclosed. A linear floating voltage-controlled resistor (LFVCR) is realized using a MOSFET with a gate drive means and a substrate drive means to provide a feedback of the common-mode voltage across the source-drain terminals to the gate and substrate terminals. Two such LFVCR circuits using matched MOSFET devices having independent substrates, along with an op-amp based negative feedback loop, are used to realize a continuously variable precision and linear floating resistor, whose value can be controlled by a combination of variable voltage, current, and resistor. Further embodiments are disclosed for realizing a resistor mirror circuit with multiple floating resistors, improving the linearity by using LFVCR circuits with complementary MOSFET devices, realizing a resistor with scaled-up resistance and extended voltage range, and realizing a resistor with scaled-down resistance and extended current range.

Abstract: A circuit for realizing a precision and linear floating resistor, using MOSFET devices, is disclosed. A linear floating voltage-controlled resistor (LFVCR) is realized using a MOSFET with a gate drive means and a substrate drive means to provide a feedback of the common-mode voltage across the source-drain terminals to the gate and substrate terminals. Two such LFVCR circuits using matched MOSFET devices having independent substrates, along with an op-amp based negative feedback loop, are used to realize a continuously variable precision and linear floating resistor, whose value can be controlled by a combination of variable voltage, current, and resistor. Further embodiments are disclosed for realizing a resistor mirror circuit with multiple floating resistors, improving the linearity by using LFVCR circuits with complementary MOSFET devices, realizing a resistor with scaled-up resistance and extended voltage range, and realizing a resistor with scaled-down resistance and extended current range.

Abstract: Increasing the level of the consonant segments relative to the nearby vowel segments, known as consonant-vowel ratio (CVR) modification, is reported to be effective in improving speech intelligibility by listeners in noisy backgrounds and by hearing-impaired listeners. A method along with a system for real-time CVR modification using the rate of change of spectral centroid for detection of spectral transitions is disclosed. A preferred embodiment of the invention using a 16-bit fixed point processor with on-chip FFT hardware is also presented for real-time signal processing. It can be integrated with other FFT-based signal processing in communication devices, hearing aids, and other systems for improving speech perception under adverse listening conditions.

Abstract: A method for speech enhancement in speech communication devices and more specifically in hearing aids for suppressing stationary and non-stationary background noise in the input speech signal signals is disclosed. The method uses spectral subtraction wherein the noise spectrum is updated using quantile-based estimation without voice activity detection and the quantile values are approximated by dynamic quantile tracking without involving large storage and sorting of past spectral samples. The technique permits use of a different quantile at each frequency bin for noise estimation without introducing processing overheads. The preferred embodiment uses analysis-modification-synthesis based on Fast Fourier transform (FFT) and it can be integrated with other FFT-based signal processing techniques used in the hearing aids and speech communication devices.

Abstract: Dynamic range compression in the hearing aids is provided for restoring normal loudness of low level sounds without making the high level sounds uncomfortably loud. An apparatus along with a method using sliding-band compression is disclosed for significantly reducing the temporal and spectral distortions generally associated with the currently used single and multiband compression techniques. It; uses a frequency-dependent gain function calculated on the basis of auditory critical bandwidth based short-time power spectrum and the specified hearing thresholds, compression ratios, and attack and release times. It is realized using FFT-based analysis-synthesis and can be integrated with other FFT-based signal processing in hearing aids and audio systems.

Abstract: A method for speech enhancement in speech communication devices and more specifically in hearing aids for suppressing stationary and non-stationary background noise in the input speech signal signals is disclosed. The method uses spectral subtraction wherein the noise spectrum is updated using quantile-based estimation without voice activity detection and the quantile values are approximated by dynamic quantile tracking without involving large storage and sorting of past spectral samples. The technique permits use of a different quantile at each frequency bin for noise estimation without introducing processing overheads. The preferred embodiment uses analysis-modification-synthesis based on Fast Fourier transform (FFT) and it can be integrated with other FFT-based signal processing techniques used in the hearing aids and speech communication devices.

Abstract: Increasing the level of the consonant segments relative to the nearby vowel segments, known as consonant-vowel ratio (CVR) modification, is reported to be effective in improving speech intelligibility by listeners in noisy backgrounds and by hearing-impaired listeners. A method along with a system for real-time CVR modification using the rate of change of spectral centroid for detection of spectral transitions is disclosed. A preferred embodiment of the invention using a 16-bit fixed point processor with on-chip FFT hardware is also presented for real-time signal processing. It can be integrated with other FFT-based signal processing in communication devices, hearing aids, and other systems for improving speech perception under adverse listening conditions.

Abstract: Dynamic range compression in the hearing aids is provided for restoring normal loudness of low level sounds without making the high level sounds uncomfortably loud. An apparatus along with a method using sliding-band compression is disclosed for significantly reducing the temporal and spectral distortions generally associated with the currently used single and multiband compression techniques. It; uses a frequency-dependent gain function calculated on the basis of auditory critical bandwidth based short-time power spectrum and the specified hearing thresholds, compression ratios, and attack and release times. It is realized using FFT-based analysis-synthesis and can be integrated with other FFT-based signal processing in hearing aids and audio systems.