Wk5c-Electric and Acoustic Stimulation Flashcards
What does EAS stand for?
Electric and Acoustic Stimulation - typically combined stimulation in same ear
Bilateral CI = ?
Two CI’s - one in each ear
Bimodal = ?
CI + HA; typically refers to a CI in one ear and a hearing aid in the other, notwithstanding that unilateral EAS is technically also “bimodal”
EAS refers to severely impaired acoustic hearing, not ___ -impaired acoustically aided hearing
Moderately
An EAS candidate is somewhere between a CI candidate and a hearing aid candidate - they would have a ___ to ____ SNHL in the low frequencies and a profound hearing loss in the higher frequencies >1-1.5 kHz. They would also need inadequate speech comprehension in best aided condition, and no progressive HL.
Mild to moderate in low frequencies - if LF thresholds are worse than 60 dB, then a regular, full-length CI is a better choice
- worse than 80 dB in high frequencies (un-aidable)
___% of CI candidates now have bilateral residual LF hearing before surgery
80
What are the pros and cons of electric hearing?
Pro: restores hearing to severe/profoundly impaired high frequency regions
Cons:
- poor spectral resolution
- envelope-based processing discards waveform fine structure
- typically doesn’t reach LF apical regions
- invasive
When comparing speech samples in quiet, noise, and vocoded in quiet, what one thing does the vocoded-quiet sample not tell us that the other two do?
Pitch period (discovered using autocorrelation)
What is autocorrelation?
Methodology to discover the pitch in discrete speech samples
-the sample of rate or amplitude in an interval defined b/w two frequencies with amplitude>30% of the initial energy represents the frequency of pitch
In the simulated EAS signals, frequencies below ___ Hz are simulated acoustically, and above that are simulated with the vocoder
500 Hz
What can acoustic low frequency input do?
- improve speech perception in quiet and noise
- improve pitch and melody perception
- helps with segregation of simultaneous sounds
- improves sound quality
What are the 4 possible ways acoustic stimulation can be provided?
- hearing aid contralateral to CI
- hearing aid in same ear as CI (2 devices)
- combined CI+HA device in one ear
- various combinations (e.g. 1 +3, 3+3)
The Med-EL duet is an example of a _____ device
Combined CI+HA device
- low frequencies provided through HA and mold
- high frequencies provided through CI
- key factor is the length of the electrode array (keep cochlear apex as alive as possible and reduce trauma; sometimes electrode arrays are as small as 10mm)
In the study by Gantz et al (2005) what was the mean LF shift (125-1000Hz) pre and post-operatively?
9.5 dB loss
Pre-shaped electrodes need more insertion force and make it ____ (easier/harder) to preserve hearing
Harder; once in the cochlea, they try to reach their pre-shaped shape, so extra tension is added locally
What are a few key characteristics of EAS surgery?
- special atraumatic soft electrodes
- smallest possible acoustic trauma d/t cochleostomy drilling (low speed)
- smallest possible mechanical trauma d/t drilling and electrode insertion
- avoid inflammatory and fibrotic reactions (contamination with blood, bone dust, ME bacteria, etc.)
- use of drugs that will aid in preserving hearing
- use of round window insertion vs traditional cochleostomy
We would expect to see better results with ____ (different/same) gender masker
Different
We would expect to see ____(better/similar) results with EAS compared to CI alone
Better (superadditivity)
How much low frequency info is needed for benefit (according to Zhang et al’s research)?
Any added acoustic input improved performance, but even with minimum (125 Hz) input made a significant difference compared to CI alone (more so in noise than in quiet)
Brungart et al (2001) found that performance decreased with ___ (lower/higher) SNR
Lower
Regarding the characteristics of speakers and masking talkers, Brungart et al (2001) found that speech intelligibility was best when______ and worst when_______
- Target and masking talkers were different genders
- Target and masking talkers had similar characteristics
- Also, in most conditions, listeners performed better when exposed to talker characteristics prior to testing.
How is segregation problematic under CIS?
-Female talkers are easier to hear (possibly d/t higher frequency), but we still cannot distinguish the gender of the voice
How did adults using CI+HA describe sound quality?
- more natural and melodious voices
- better balance
- louder and clearer speech at meetings
- music and tv is better
- easier to identify the speaker at round-table discussions
- better coordination
How does complementary acoustic stimulation (Bimodal/EAS) help?
- good frequency resolution and temporal fine structure allow listener to resolve LF harmonics
- provides pitch info for melody, voice segregation, and SIN
- provides important voicing info for speech signal
