challenging Flashcards
CI USERS MAINLY USE _______.
ILD
ILD show better performance in
anechoic, but you cant really use ILD in reverberant environment
The electrical stimulation sequences provided in CIs are affected by the noise in the following three manners.
1) natural gaps in the speech are filled, which distorts the low-frequency ON/OFF modulations of the speech signal.
2) speech envelopes are distorted to include modulations of both speech and noise.
3) N-of-M type of speech coding strategies may select the noise dominated channels instead of the dominant speech channels at low signal-to-noise ratio’s (SNRs).
“picking the wrong peaks”
Qazi findings
modulations in the stimulus current level have no effect on speech intelligibility as long as the channel selection remains ideal.
at low SNR
wrong maxima selection creates interruptions in the speech and makes it hard to fuse noise and interrupted speech signal together
Qazi et al
Normal vs CI
CI subjects can tolerate significantly lower levels of steady state speech shaped noise in the speech gaps but at the same time can tolerate comparable levels of distortions in the speech segments.
ILD ITD localization in reverberation
Kerber and seeber
srinivasan et al
improving speech in noise using current focusing
current focusing
reduce spread of excitation and reduce channel interaction
potential problem with TP
TP stimulation is that larger current amplitudes are required to reach adequate loudness levels, may not be possible due to compliance issues
tripolar stimulation
TP stimulation uses 2 intra-cochlear electrodes (adjacent to the active stimulating electrode) as grounds (see Fig. 1). By keeping the current loop entirely within the cochlea, the intra-scalar voltage gradient is steeper than for MP stimulation, possibly leading to more focused neural excitation.
partial tripolar (PTP) stimulation
a fraction of the current is returned via the intracochlear electrodes and the remainder is returned via the extracochlear electrode, similarly to MP stimulation
cochlear ADRO + ASC (malls or music venue)
automatic dynamic range optimization
- soft sounds audible loud comfortable.
- gains adaptively adjusted to maintain stim in upper 50% of DR
ASC - autosensitivity - reach of the processor
-auto adjust mic sensitivity
cochlear Zoom
fixed directional mic best where noise source does not move, 2 omni mics
conversation in mod noise
3.5 time improvement over previous
cochlear beam
focused listening in noise
speaker in front and noise to sides and behind
locks on to voices from front
directional and omni directional mic combined.
