Loudness and Dynamic Range in Cochlear Implant Listeners

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Loudness and Dynamic Range in Cochlear Implant
Listeners

• Michelle Husain
• Department of Mathematical and Physical Sciences
• Dec.10,2003

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Background

• Importance of hearing/deafness.
• Way the normal hearing process works
• Deafness
• Cochlear implants history
• How cochlear implants work
• Challenges in cochlear implant technology

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Normal Hearing

• Outer-gtmiddle-gtinner ear-gtauditory nerve-gtbrain

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Deafness

• Conductive - damage to the outer and middle part
  of the ear it usually can be treated hearing
  aids can be used. E.g, ear infections.
• Sensorineural some or most of hair cells in the
  cochlea die .Hearing aids can only amplify sounds
  they can hear.
• Mixed-combination
• Mild hearing loss (35 to 54 dB)
• Moderate hearing loss (55 to 69 dB)
• Profound hearing loss (90 dB and beyond)

• Intensity in Decibels (dB) Examples
• 140 Jet plane taking off about 100 feet
  away
• 130 Jackhammer
• 120 Rock and roll concert
• 110 Train
• 100 Lawnmower or Chain saw
• 90 Car horn honking
• 80 Telephone ringing
• 70 Dog barking
• 60 Vacuum cleaner
• 50 Conversations
• 40 Quiet radio
• 30 Watch ticking
• 20 Whisper
• 10 Leaves moving

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Hair cells frequency encoding
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History of Cochlear Implants

• Count Volta1770- connected batteries to two metal
  rods - 'jolt in the head.
• 1855 Duchenne of Boulogne, trapped insect sound
• First direct stimulation of the auditory nerve in
  1950s. They were able to transmit a signal to
  the electrode via a radio antenna on the outside
  of the body.
• Multiple electrodes were stimulated in the
  cochlea by American surgeons in 1964,implanted
  six electrodes with success.
• Nucleus 22

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Cochlear implants
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Implant characteristics

• Electrode design

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• Types of stimulation Analog Pulsatile
• Transmission link Transcutaneous percutaneous.

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Nucleus 22 processor
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ISR

• Dr. Robert Smith(SU) his team , Bioengineering
  Neuroscience department of ISR
• Funded by by the National Organization for
  Hearing Research.
• Dr. Bingabr(Wells), measuring loudness by
  developing a graphical user interface program
  that delivers electric pulses to the human audio
  nerve through cochlear implant.

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Problem

• Sequence -gtelectrode
• Does not go through outer, middle ear
• Hence bones fluids cannot equilibrate sound the
  way the ear does naturally and it must be done
  through the software in the cochlear implant
  package.

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Tasks

• Develop algorithm
• Write code in Visual C6.0 software in MFC
• Test it on patients

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Biphasic stimulator