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Speech Strategy for the Cochlear Implant

Speech Strategy for the Cochlear Implant. Senior Design Fall 06 and Spring 07. Outline. Sound and Speech The Biological Auditory System The Electrical System of the Cochlear Implant Challenges Facing the Cochlear Implant Users Senior Design Task. Fourier Series. 100 Hz. Time Domain.

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Speech Strategy for the Cochlear Implant

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  1. Speech Strategy for the Cochlear Implant Senior Design Fall 06 and Spring 07

  2. Outline • Sound and Speech • The Biological Auditory System • The Electrical System of the Cochlear Implant • Challenges Facing the Cochlear Implant Users • Senior Design Task

  3. Fourier Series 100 Hz Time Domain 200 Hz Time 300 Hz Frequency Domain 400 Hz 100 200 300 400 Frequency

  4. Speech Sound wave at the lips and at the glottis for the letter “O”. Source Function Glottal Pulses Transfer Function Resonance of Acoustic Tube 17 cm fo=100Hz Relative Amplitude (dB) 20 Relative Amplitude (dB) 1000 2000 3000 Freq. 500 1500 2500 Freq. Output Product of Source and Transfer Functions Relative Amplitude (dB) Freq. F1 F2 F3

  5. Spectrogram Bab Dad Gag

  6. Biological Hearing System Cochlear Tympanic Membrane Ossicles Bones Basilar Membrane Inner Hair Cells Sound S(t) NT(t) = Glutamate Spiral Ganglion Cells & Cochlear nerve Oval Window Auditory Pathways & Auditory Cortex

  7. Frequency of Sound (Pitch) Hard bone Basilar Membrane Inner Hair Cells Apex Base Auditory nerves

  8. Electrical and Biological Hearing System Cochlear Implant Sound S(t) Speech Processor Electrodes Microphone EP(t) Spiral Ganglion Cells & Cochlear nerve Auditory Pathways & Auditory Cortex

  9. Speech Processor

  10. Speech Strategies • Continuous Interleaved Sampling (CIS) • n-of-m and Advanced Combination Encoder (ACE) • Spectral Peak (SPEAK) • Simultaneous Analog Stimulation (SAS) • High Resolution (HiRes)

  11. Sound Simulation • Increase channels 1 > 2 > 4 > 8 > 16 > 32 > Original • Decrease Channels Original > 38 > 16 > 8 > 4 > 2 > 1 • Song 4 > 8 > 16 > 32 > Original • Music > 4 > 8 > 16 > 32 > Original

  12. Sin(2πf1Ct) Rect./ LPF1 BPF1 Sin(2πf2Ct) Rect./ LPF2 BPF2 Input Speech Signal Output Speech Signal Sin(2πfnCt) Rect./ LPF n BPF n Find the Optimum number of Channels f1C f2C fnC f1L f2L f3L f4L f5L fnL 4000Hz

  13. Senior Design Tasks • Learn the mechanism of human speech production and the important components of speech for speech intelligibility. • Learn the mechanism of human hearing system. • Search the literature for the current speech strategies and processors. You may need to contact manufacturers for the speech strategies of their speech processor. • Design and simulate a speech processor with the optimum number of channels to achieve speech intelligibility in a quite environment. • Test your design with a speech in a noisy environment. If speech intelligibility deteriorate then modify your design to improve speech intelligibility. • Build your speech processor and test it with a real speech signal in both quite and noisy environments. • Investigate the effects of channel interactions.

  14. Skills Needed for the Cochlear Implant Project • Ability to read the literature. • Ability to use Matlab and Simulink to run circuit simulations. • Ability to use Fourier analysis and software to analyze the frequency components of speech. • Ability to build electrical filters, multiplier, summer, and rectifier. • Organization, determination, and team work ethic.

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