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AUDE 6450 > final exam new info > Flashcards

final exam new info Flashcards

(49 cards)

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1
Q

external sound components

A

microphone, digital sound processor, coil/antenna, magnet and power source

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2
Q

internal implant components

A

magnet, receiving/transmitting coil, digital sound processor, stimulator for electric pulse generator, electrode leads and electrode arrays

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3
Q

in general, how does a CI convert sound into electrical stimulation

A
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4
Q

importance of the speech processor

A

it functions like the cochlear within the implant and it is where everything occurs in order for the signal to be digested

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5
Q

what are the main processes of the speech processor

A

amplification, filter, envelope detection, compression and modulation

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6
Q

amplification within the speech processor

A

used to increase signal levels and the exact level is determined by the gain of the amplifier which is defined by the ratio of output to input level
-this is the first step that occurs!

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7
Q

why is amplification necessary within the speech processor

A

ensures that the end signal can be detected and heard well by the patient

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8
Q

filtering within the speech processor

A

used to divide the emphasized signal into multiple frequency bands using a filter bank, designed to mimic the natural tonotopic organization of the cochlear
-typically will use bandpass filtering, and the amount of filters corresponds with the amount of electrodes
-it is a one to one relationship with the channel and the electrode

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9
Q

how many channels does each manufacturer offer?

A

cochlear: 22
AB: 16
MED-EL: 12

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10
Q

what does it mean when we say that CI filtering relies on fourier analysis

A

this analysis is a method that decomposes complex functions/signals into simpler components, typically as a sum of sine and cosine waves
-relating to how the cochlear is organized so the stimulation needs to be completed in a similar way

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11
Q

the cochlear implant is essentially an analyzer. what does this mean in terms of the incoming signal and hearing?

A

it takes the incoming signal and divides it into a set amount of different components
-these components are then sent to the electrodes to stimulate the appropriate nerve fibers

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12
Q

the main goal of filtering within the speech processor

A

trying to mimic the tonotopicity of the natural cochlea

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13
Q

envelope detection within the speech processor

A

the envelope of the signal is created by using both a rectifier and a low pass filter
-remember, the envelope is the smooth overarching line that follows the waveform

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14
Q

rectification within envelope detection

A

takes anything that is negative and flops it to become positive, making it easier for the CI to process

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15
Q

purpose of envelope detection

A

this gives the overarching information that is needed from each frequency band, giving a more broad spectrum of input
-the CI cannot process both spectral and temporal information so the envelope helps simplify the signal

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16
Q

compression within the speech processor

A

this takes the incoming signal, compresses it to make it fit into the narrow electrical DR in order to make it suitable for stimulation
-this helps ensure that those signals of interest can be audible

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17
Q

purpose of compression

A

cuts out quieter sound levels that are considered not useful and resets louder sounds to a constant level

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18
Q

with CI patients they have a very very narrow dynamic range so ….

A

when we increase the signal we want them to identify it as an increasing amount so without compressing the signal this perception would not occur within the patients

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19
Q

modulation within the speech processor

A

biphasic pulses are generated with amplitudes proportional to the energy of each channel
-it takes the amplitude that has been compressed and a pulse is generated that is similar to the amplitude and frequency of each band, given to each individual electrode

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20
Q

purpose of speech coding strategies

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A

it describes the algorithm used by the speech processor to transform the important features of the incoming signal into an electrical code that can be delivered to the implant
-these strategies are the instructions!

21
Q

why are speech coding strategies necessary

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A

they help decide what information to keep, what to simplify and how to deliver that
-additionally they attempt to condense the incoming signal for a suitable transmission of an electrical signal

22
Q

two main groups of speech coding

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A

feature extraction and waveform strategies

23
Q

feature extraction coding strategies

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A

this focuses on the frequencies, spectral cues and uses algorithms to help each band extract some spectral information that is used to generate the stimulus to the electrodes
-includes F0/F2, F0/F1/F2 and the mpeak strategy

24
Q

F0/F2 strategy

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A

taking the band and only extracting the F0 and F2
-developed originally for the nucleus and results were encouraging

25
F0/F1/F2 strategy
taking the band and within each one they extracted the F0, F1 and F2 -this alteration showed a WRS increase however was not significant enough to yield major benefits for the patients -still showed many errors within the consonants
26
mpeak (multipeak) strategy
included the F0/F1/F2 but added the high frequency information to be extracted as well -created to improve the representation and perception of consonants -this emphasized the HF range -showed an improvement in consonant identification and on open set sentences however still had difficulty in noise
27
waveform coding strategies
focusing on the temporal envelope, aiming to present some type of waveform derived by filtering the speech signal into different frequency bands and mainly focusing on the timing aspect -including N of M, ACE, HiRes and HDCIS
28
N of M strategy
with this one, every electrode has the chance of being stimulated but not everyone is stimulated at once -the number of electrodes that is stimulated is referred to as n -early strategies were SMSP and SPEAK
29
SMSP vs. SPEAK
SMSP: the first N of M in which 6 electrodes would be stimulated SPEAK: 6-10 are selected to be activated
30
with N of M strategies, how are electrodes selected for stimulation
based on those that have the largest amplitude (maxima)
31
advanced combination encoder (ACE)
an N of M strategy that has high stimulation rates (14,400) and activates the electrodes with the channels that have the highest amplitude -this is the default for many manufacturers -additionally there is the High ACE which has an even faster stimulation rate
32
continuous interleaved sampling (CIS)
signal is sent through a bank of bandpass filters that is separated into discrete frequency bands in which the temporal envelope is extracted, then compressed and converted into interleaved electric pulses -only activating one electrode at a time
33
what is channel interaction and how does CIS limit this?
channel interaction occurs when 1 electrode is activated and a nearby electrode becomes activated as a result of the other -CIS only activated one electrode at a time and makes sure to put a brief pause between (but the pause is very fast we cannot even notice it)
34
what is an alteration of CIS
MPS (multiple pulsatile sampler) -allows for doubling of stimulation rate, improving speech recognition -this provides simultaneous stimulation where two electrodes are activated at once but they are not electrodes next to each other
35
what is the difference between CIS and n of m strategies in terms of electrode stimulation?
CIS selects one electrode at a time (or 2) based on the incoming signal timing whereas n of m selects the electrodes with the largest amplitude
36
HiResolution (HiRes)
higher stimulation rate with higher cutoff frequencies for low pass filters -this keeps the same temporal resolution within the signal -however, limits how fast the tracing occurs
37
HiRes fidelity 120
creates phantom channels in which the place between is stimulated
38
high definition CIS (HDCIS)
allows for a broader frequency range with the option to extend the lower limit to 70 Hz, used only by MED-EL -utilizes transformation, meaning it takes the wave and shifts it so that they do not start at the same time giving more envelope information -gives a more complex signal with high amounts of temporal information
39
how doe HiRes fidelity 120 and HDCIS strategies create virtual channels
HiRes creates virtual channels by current steering the voltage between electrodes whereas HDCIS creates virtual channels by using overlapping frequency filters during signal processing
40
fine structure processing (FSP)
a version of CIS that extracts spectral, envelope and fine temporal structure information from the input signal -used only with MED-EL
41
what is a coding strategy that is thought to help music appreciation
fine structure processing (FSP)
42
components of the electrode design
electrode array, electronics, titanium housing, gold coil, magnet and complete product
43
the electrode vs. electrode array
electrode: the physical structure that injects current to the tissue electrode array: the distal part that contains the electrode contacts
44
the electrode array comes in difference shapes and lengths, what are some possible types
45
describe how the current travels within the electrode array/electrodes
46
intracochlear electrode contacts
this is where the current is injected into the neural tissue -these come in different shapes and designs -vital for them to be facing the correct way as we want them to go to the right neural area
47
monopolar stimulation
48
bipolar stimulation
49

AUDE 6450 (2 decks)

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