Download Artificial cochlear implants Geoff

Artificial Cochlear Implants
Geoff Norman
4/18/16
 Abstract: Cochlear implants are surgically implanted
electronic devices which allow people who are deaf to
have a sense of hearing. These devices work by
picking up sound waves thorough a microphone
which then transmits electrical signals to electrodes
that are planted within the cochlear nerve. Once a
microphone signal is received the electrodes
stimulate the cochlear nerve which then sends signals
to the brain that simulate hearing.
Outline
 Brief history of artificial hearing.
 How are cochlear implants different from normal
hearing?
 Summary of normal hearing.
 Summary of cochlear implant hearing.
 How does a cochlear implant work?
 Overview of circuit architecture.
 Breakdown of circuit architecture into main
components.
 Example of normal vs implant hearing.
Brief History of Artificial Hearing
 Early 19th century: Alessandro Volta stimulates inner
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ear using a battery and two metal rods.
1930: Wever and Bray discover that electrically
stimulating the auditory nerve with electrodes was
similar to stimulation using sound waves.
1950: Lundberg stimulates auditory nerve using
electricity while performing surgery.
1972: Speech processor developed.
1984: FDA formally approves cochlear implants for use
in patients with severe hearing loss.
Mechanisms of Normal Hearing
 Outer Ear
 Consists of Pinna, Ear Canal,
and Eardrum.
 Captures and locates sound
sources.
 Middle Ear
 Consists of the Malleus, Incus,
and Stapes.
 Transmits vibrations from the
Eardrum to the Inner Ear.
 Inner Ear
 Consists of Cochlea, organ of
Corti, and Basilar Membrane.
 Converts vibrations to
spatiotemporal patterns.
[1]
Mechanisms of Cochlear Implant Hearing
 External Devices
 Microphones
 Speech Processor
 Transmitter
 Internal Devices
 Receiver
 Stimulator
 Electrode Array
[4]
Cochlear Implant Architecture
[6]
Microphone
 Piezoelectric microphones are typically used.
 When the piezoelectric material is stressed along one axis
it induces a potential difference across an orthogonal axis
thereby directly transducing pressure waves into electrical
waves.
 Broad frequency spectrum that
doesn’t extend to low frequencies to
avoid picking up head movements.
[10]
Speech Processor
 Decomposes complex signals from the microphone into discrete
electrical signals.
 Upon entering the speech processor frequency resolution is performed
on the signals to split them into their frequency components.
 Once split into their frequency components amplitude compression is
performed to lessen the effect of the
effect of louder signals and to amplify the
effect of quieter signals.
 Finally, pulse modulators are used to
turn the various signals into biphasic
pulses that can be transmitted to the
stimulator.
[8]
Transmitter/Receiver
 Consists of an encoder, a decoder, an external
transmitting coil and an internal receiving coil.
 Signals from speech processor are encoded and sent
from external coil to internal coil.
 Once the signal is received by the internal coil it is
decoded and sent to the stimulator.
[9]
Stimulator/Electrode Array
 The stimulator receives the decoded electrical signal from
the receiver coil and uses the signal to properly stimulate
the electrode array at various positions.
 The electrode array is placed within the cochlea and when
stimulated properly will cause the ganglion cells to send
impulses to the part of the brain responsible for hearing.
[10]
Example of Cochlear Implant Sound
[5]
References
 [1] Appalachian State,
http://www1.appstate.edu/~kms/classes/psy3203/Ear/Eardrawing1.jpg. 2016.
 [2]"Cochlear implant", Wikipedia, 2016. [Online]. Available:
https://en.wikipedia.org/wiki/Cochlear_implant#Efficacy. [Accessed: 09- Apr2016].
 [3]"Hearing", Wikipedia, 2016. [Online]. Available:
https://en.wikipedia.org/wiki/Hearing. [Accessed: 09- Apr- 2016].
 [4]"About Cochlear Implants — The Children's Cochlear Implant Center at
UNC", Med.unc.edu, 2016. [Online]. Available:
https://www.med.unc.edu/earandhearing/listening/about-cochlear-implants1. [Accessed: 09- Apr- 2016].
 [5]"Hearing Cochlear Implants w/ open captions - YouTube", Youtube.com,
2012. [Online]. Available: https://www.youtube.com/embed/00WOao4kpwM.
[Accessed: 09- Apr- 2016].
 [6]"Human-Embedded Computing", www.cs.uaf.edu, 2009. [Online].
Available: https://www.cs.uaf.edu/2009/fall/cs441/proj1/natasa/index.html.
[Accessed: 09- Apr- 2016].
References (continued)
 [7]"History of Cochlear Implants timeline.", Timetoast, 2016. [Online].
Available: https://www.timetoast.com/timelines/history-of-cochlear-implants.
[Accessed: 10- Apr- 2016].
 [8]"Understanding The Cochlear Implant: Components : Speech Processor",
Biomed.brown.edu, 2006. [Online]. Available:
http://biomed.brown.edu/Courses/BI108/2006108websites/group10cochlearimplant/pages/speechprocessor.htm. [Accessed:
10- Apr- 2016].
 [9]"Electrodes and Channels", cochlear implant HELP, 2012. [Online].
Available: https://cochlearimplanthelp.com/journey/choosing-a-cochlearimplant/electrodes-and-channels/. [Accessed: 13- Apr- 2016].
 [10]"Microphones", Hyperphysics.phy-astr.gsu.edu, 2016. [Online]. Available:
http://hyperphysics.phy-astr.gsu.edu/hbase/audio/mic3.html. [Accessed: 14Apr- 2016].
Summary of Key Points
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Cochlear implants are electrical devices that can be implanted
directly into a deaf patient that allows the patient to experience a
simulation of hearing.
Piezoelectric microphones are used to transduce sound waves into
electrical signals that can be used by the implant to simulate sound.
A speech processor is used to take the complex microphone signal
and decompose it into discrete electrical signals which are easier to
interpret.
A radio frequency receiver and transmitter are used to send the
speech processor data to the stimulator and electrode array.
An electrode array is used to directly stimulate the cochlea with
different electrical signal that represent the original sound waves
frequency and amplitude.