Introduction to cochlear implants given to freshmen engineering students at Ohio Northern University

1. Re-Engineering Hearing: Introduction to Cochlear Implant Design Dr. Ryan Clement 04/30/08 GE 106: Freshman Engineering 3

4. Normal Hearing- Anatomy External ear Middle ear Inner ear (cochlea)

5. How Do We Normally Hear? Sound enters ear… Ear drum the eardrum and middle ear bones vibrate… which creates a fluid wave in the cochlea… Transduced to neural impulses for brain to interpret

6. The Cochlea: Sound to Neural Impulses http://www.iurc.montp.inserm.fr/cric/audition/ Cross-section of Cochlea http://www.bcm.edu/oto/research/cochlea/Hearing/

7. Transverse Sound Wave Hair Cells Auditory Nerves To Brain

8. Sound and Frequency Pressure Time High Frequency Low Frequency

9. Tones and the Cochlea High frequency Low frequency

10. Frequency Spectrum of Tones Power/Magnitude Frequency Power Spectrum Gives an indication of what frequencies are present in complex signals Time Domain Frequency Domain Summed signal +

11. Complex Sound Spectrum Complex sounds can be decomposed into individual frequency components… Signal vs. Time Frequency Spectrum 200Hz 400Hz 800Hz 1600Hz 3200Hz 200Hz 400Hz 800Hz 1600Hz 3200Hz

12. Speech- Frequency Spectrum of Vowels a e i o u 6 kHz 0 kHz Frequency Power

13. Spectrograms “ Discover your true north” Power spectrum plotted vs. time 1.5 2.0 2.5 Time (seconds) 10k 1k 100 Frequency (Hz) Speech signal vs. time Di- -s- -c o v- er y- our t- r- ue N- o r th

14. The Cochlea is a Frequency Analyzer! Un-coiled Cochlea Low Freq Hi Freq

16. Electric Activation with Cochlear Implant Hair Cells Auditory Nerves

18. Cochlear Electrode Array Cochlear Electrode Cochlea Auditory Nerve Cochlear Corporation’s Nucleus Electrode

19. What Do Cochlear Implants Sound Like? 1 Channel 4 Channel 8 Channel 2 Channel base apex

20. Auditory neuron cell bodies Electrode 1 Electrode 2 Activated Cells Activated Cells Independent Activation!

21. Electrode 1 Electrode 2 Channel interaction Increased Distance

22. Design Problem

24. Actual Solutions- Advanced Bionics Electrode Positioner* *been attributed to 9 menengitis-related deaths and is no longer used

25. Actual Solutions- Cochlear Corporation The Nucleus Contour features a self-curling electrode array A stylet keeps the array straight during insertion, and then is removed by the surgeon The array then hugs the center of the cochlea (where the auditory neurons are)

26. COCHLEAR IMPLANT ETHICS

29. Ethical Dilemmas- Cochlear Implants Imagine that you and your spouse are deaf. Your child is born without hearing. Would you go forward with the implant? What are all the issues you would consider? Would your reasoning change if you both could hear?

32. Speech Processing

33. Performance Results

34. Dorman 2002