Challenging Listening Environments Flashcards
How is electrical stimulation of CIs impacted by noise?
- Natural gaps of speech are filled w/ noise
- Speech envelopes are distorted to include modulations of speech and noise
- N-of-M speech coding strategies may select noise-dominated channels at low SNRs
Why does speech perception in noise degrade in comparison with performance in quiet for CI users?
- Broad current spread from stimulating and adjacent electrodes
- Activation of overlapping populations of neurons
What is tripolar (TP) stimulation?
- Monopolar stim uses an extracochlear electrode as ground
- TP utilizes 2 intracochlear electrodes adjacent to the stimulating electrodes
- By keeping the current in the cochlea, voltage gradient is steeper, leading to more focused neural excitation
- TP required is larger amplitudes to achieve adequate loudness (compliance issues)
What is partial tripolar (PTP) stimulation?
-A fraction of the stimulation goes to the adjacent electrodes, and the rest goes to an extracochlear electrode (combo of TP and MP)
Because of spread of excitation increases as amplitude increases and larger amplitudes are required for PTP, is there any difference between PTP and MP?
- Landsberger et al. (2012)
- PTP reduces spread of excitation with equal loudness levels compared to MP
- With all other variables controlled, current steering such as PTP can result in improved speech perception in noise
What 2 factors are most important for sound localization in challenging environments?
- ITDs
- ILDs
How do ITDs help with sound localization in challenging environments?
- Envelope of the signal
- Used for localizing low-frequency signals
How do ILDs help with sound localization in challenging environments?
- Used for localizing high-frequency signals
- CI users mainly use ILDs
How does forward masking relate to sound localization?
- Hypothesize that faster forward masking decay might lead to greater perceptual segregation between direct sound and reflections (less influence from reverberation):
- Localization in reverberation declined significantly
- Forward masking decline had little predictive value
What did direct stim measures reveal about localization declines in reverberation?
- Sensitivity to ILDs predicted localization performance in anechoic environments (quiet)
- Sensitivity to ITDs predicted performance in reverberation and decline in performance in reverberation
What SmartSound settings are offered by Cochlear?
- Everyday (ADRO + ASC)
- Noise (Zoom + ADRO + ASC)
- Focus (BEAM + ADRO + ASC)
- Music (Whisper + ADRO)
What is ADRO?
- Automatic dynamic range optimization
- For listening in challenging and dynamic environments
- Soft sounds audible while loud sound are comfortable***
- Dynamically adjusts the gain of each channel independently based on input level, level of BGN, and level of loudest sounds
- Channel gains are adaptively adjusted to maintain the signal in the upper 50% of the DR (loud but comfortable)
- Adjusts frequency emphasis according to input spectrum and dynamics of ambient noise levels
What is ASC?
- Autosensitivity
- Comfort when listening in noisy environment
- Noise suppression algorithm; dynamically adjusts mic sensitivity in response of level of BGN
- Aims to ensure that the noise floor remains at 15 dB below the sound that triggers AGC
What is ZOOM?
- Provides best possible hearing in noisy environments
- New in N5 processors
- 2 omnidirectional mics
- SIN performance 3.5x better than Freedom
What is BEAM?
- Focused listening in noise
- 2 stage algorithm: 1) directional and omnidirectional mic outputs are combined to produce a more directional beam pattern, and 2) voice detection algorithm “locks on” to voices from the front
