Wk5a - Other Speech Processing Strategies Flashcards

1
Q

Name two variations of CIS

A

SPEAK (Spectral Peak; obsolete)

ACE/n-of-m

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2
Q

What does SPEAK stand for? How does it work?

A

Spectral Peak

  • it stimulates a variable number of electrodes at a low pulse rate (~250 pps) compared to CIS (~1000 pps)
  • the electrodes corresponding to the 6-10 highest amplitude channels are stimulated
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3
Q

With the SPEAK speech processing strategy, the number of channels is adaptive. What 2 things determine the number of channels used?

A

Input level

Spectrum

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4
Q

What speech processing strategy superseded SPEAK?

A

ACE

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5
Q

Describe how the SPEAK processing strategy processes an acoustic signal?

A
  • The waveform is passed through a 22 channel bandpass filter bank
  • At a single moment in time, the filter-bank output envelopes are evaluated and the 6 channels with the largest output results in stimulation of the corresponding electrodes
  • On another cycle, other channels might be selected
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6
Q

What does ACE stand for?

A

Advanced Combination Encoder

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7
Q

How does ACE differ from SPEAK?

A
  • combines high pulse rate (like CIS) with channel selection
  • only stimulates the electrodes corresponding to the highest n filter bank channel levels (e.g. 8 out of 16) on each cycle
  • the number of active electrodes is NON-ADAPTIVE (can be changed in the CI program by the audiologist, not changing with each cycle)
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8
Q

What is the name of the strategy of which ACE is a proprietary name of?

A

n-of-m

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9
Q

Describe the n-of-m strategy?

A
  • on each cycle, the n largest filter bank outputs will results in the stimulation of the corresponding n electrodes, out of the total m electrodes of the implant
  • n is a variable programming parameter, but does not vary c/ the incoming signal (non-adaptive)
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10
Q

What are 2 benefits of n-of-m?

A
  • maintaining fine structure

- noise reduction?

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11
Q

CIS mostly eliminates fine structure info, focussing mainly on the _______

A

Envelope

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12
Q

What 3 strategies did Med-EL use to attempt to maintain fine structure information?

A
  • FSP (fine structure processing)
  • FS4
  • FS4-p
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13
Q

How did Med-EL’s fine structure processing strategies work?

A
  • high frequency channels use CIS variants CIS+ or HDCIS (overlapping band-pass filters and Hilbert envelope extractor)
  • the fine structure was maintained in the 2-4 low frequency channels, where pulses were only emitted when the waveform crossed zero in a positive direction
  • supposedly gives listener access to additional low-freq fine structure info, helpful for pitch perception and SIN
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14
Q

With Med-EL’s FSP strategy, pulse trains were generated at each ascending zero crossing of the acoustic signal. What might determine which electrodes were programmed to receive this signal?

A

Depth of insertion - we have a rate-limit for AM sensitive of 250-300 hz
- deeper insertion = more fine structure electrodes can be employed (up to 4 c/ FSP)

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15
Q

FS4 was programmed to deliver fine structure stimulation to the 4 most ____ electrodes up to ____ Hz

A

Apical; 1000 Hz

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16
Q

Between HDCIS and FS4, which demonstrates more fine structure in the first 4 electrodes/channels?

A

FS4

17
Q

Which of Med-El’s 4 strategies used sharp filter banks and a bandwidth b/w 250-8500 Hz?

A

CIS+

18
Q

What was CIS+ upgraded to?

A

HDCIS - the same as CIS+, but with a bell-shaped filter bank

19
Q

Which Med-El strategy included fine structure in the 2-4 apical electrodes up to 470 Hz and extended bandwidth down to 100 Hz

A

FSP

20
Q

How is FS4 different from FSP?

A
  • 4 apical electrodes always stimulated to provide fine structure (vs 2-4)
  • fine structure bandwidth increased to up to 1000 Hz
21
Q

How is FS4p different from FS4?

A
  • it’s FS4 with parallel stimulation
22
Q

How does a sharp filter bank differ from overlapping?

A
  • sharp filter banks have small amount of info being carried by neighbouring electrodes (sharply tuned)
  • bell-shaped will overlap info b/w diff channels (e.g. 1kHz info carried mostly by one filter, but also a little by each on either side
  • trend is to overlapping filters (so sound “fades” b/w electrodes, instead of “jumping”)
23
Q

What is current steering?

A

Activation of multiple electrodes simultaneously

  • can stimulate diff (but maybe overlapping) populations of neurons than those from activating any single electrode
  • on-purpose channel interaction
24
Q

What changes can we expect to see to the typical bell-shaped electric field by simultaneously stimulating adjacent electrodes with the same bipolar stimulus with half the current/amplitude?

A

We would see a wider, flatter stimulus
(whereas if one electrode were stimulated with the same current and electrode 2 with half amplitude and reversed polarity, we would see the same bell shape, but with sharper/ more precise stimulation)

25
Q

How is “on purpose” interaction (current steering) being used?

A
  • to generate “virtual” channels b/w electrodes
  • using pairs of electrodes, they can vary the ratio of simultaneous pulse amplitudes for each virtual channel
    E.g. Advanced Bionics’ HiRes120 (120 channels using only 16 real electrodes)
26
Q

E.g. Using current steering to create “virtual” channels, describe the current inputs for the following:
A virtual channel is centred directly over electrode 1. How much current is it receiving from electrode 2?

A

0%; 100% of the input is from electrode 1

27
Q

E.g. Using current steering to create “virtual” channels, describe the current inputs for the following:
A virtual channel is centred a quarter of the way between electrodes 1 and 2. How much current is it receiving from electrode 2?

A

25%; 75% of the current is from electrode 1.

28
Q

New speech strategies may only work with new generation implants, or may require ________ or ________ (multiple words)

A
  • firmware updates

- new external hardware

29
Q

Acoustic pre-processing algorithms from hearing aids can generally be used in CI’s ____ (prior to, after) speech coding

A

Prior to