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

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 Time Domain 100 Hz 200 Hz 300 Hz 400 Hz 100200300400 Time Frequency Frequency Domain

4. Relative Amplitude (dB) 20 50015002500 Transfer Function Resonance of Acoustic Tube 17 cm Freq. Relative Amplitude (dB) Output Product of Source and Transfer Functions Freq. Relative Amplitude (dB) Source Function Glottal Pulses Freq. 100020003000 f o =100Hz F1F1 F2F2 F3F3 Sound wave at the lips and at the glottis for the letter “O”. Speech

5. Spectrogram BabDadGag

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

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

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

11. Speech Processor

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

13. Sound Simulation Increase channels 1 > 2 > 4 > 8 > 16 > 32 > OriginalIncrease channels Decrease Channels Original > 38 > 16 > 8 > 4 > 2 > 1Decrease Channels Song 4 > 8 > 16 > 32 > OriginalSong Music > 4 > 8 > 16 > 32 > OriginalMusic

14. 4000Hzf nL f 1L f 2L f 3L f 4L f 5L f nC f 1C f 2C BPF1 BPF2 BPF n Rect./ LPF1 Rect./ LPF2 Rect./ LPF n Sin(2πf 1C t) Sin(2πf 2C t) Sin(2πf nC t) Input Speech Signal Output Speech Signal Find the Optimum number of Channels

15. 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.

16. 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.