Sound Processing Flashcards
How many sound coding strategies offered?
7 sound coding strategies offered
AB offers more ways to hear than any other CI company.
Challenges and Opportunities
Patient Factors
duration of deafness amount of previous hearing age of hearing loss cognitive skills neural survival other
AB’s goal with challenges and opportunities
Remove technology component as a barrier to success and increase each patient’s ability to reach their maximum hearing potential
- through processor and accessory updates
- through new advances in speech coding strategies
What is a strategy
Set of rules and processes for converting the acoustic input signal into electrical stimulating waveforms that are applied as the output by a cochlear prosthesis
Strategy and its effectiveness linked to the sound processor technology and that of the ICS- directly affects how sound info is delivered to the user
Sound Processing Strategies
SAS- Simultaneous analog stimulation MSP- Multiple paired sampler CIS- Continuous interleaved stimulation HiRes-S HiRes-P HiRes-S with Fidelity 120 HiRes-P with Fidelity 120 ClearVoice HiRes Optima-S HiRes Optima-P
Sound Processors with Paired Stimulation
HiRes P
HiRes P with Fidelity 120
MPS
SPs with Sequential Stimulation
HiRes S
HiRes S with Fidelity 120
CIS
SP Strategy goals
- To faithfully represent the characteristics of the incoming acoustic signal to the listener with highest degree of fidelity
- want output of CI system to represent as closely as possible the acoustic input
- To provide a system that’s easy to use with system settings that automatically adjust based on the environment
3 parameters needed to be preserved
Time (temporal)
Frequency (spectral)
Amplitude (intensity)
Temporal representation
For best sound resolution, important to have faithful representation in time domain:
- high fidelity front-end design ensures accurate capture of acoustic environment (capture environment transparently but stimulate it transparently)
- High stimulation rates with HiRes sound allows for detailed delivery of info in time domain, including representation of both envelope and fine structure
Temporal
Conventional strategy vs. HiRes Sound
CONVENTIONAL STRATEGY
- only provides envelope (removes fine time structure)
- sample at slow rate and stimulate at faster rate
- limiting perception of dynamic sounds like music
- reduces ability to hear in difficult listening environments (car, restaurant, etc.)
HIRES SOUND
- preserves fine structure and envelope cues (normal hearing nerve uses this info)
- faster stimulation rate –> more accurate timing cues represented
- sample at higher rate and stimulate at higher rate
- output faithfully represented input with greater detail and definition, giving patient best opportunity to figure out incoming signal.
- HiRes sound provides the clearest, most accurate sound with 5x more resolution than any other CI system.
Why is Temporal info important?
Provides envelope info
- Prosody, intonation, rhythm, and stress
Provides periodicity info
- segmental (manner, voicing, vowels), intonation, stress
Provides fine structure info
- segmental (manner, voicing, place of artic)
- place of artic depends on fine structure
- fast changes in amplitude mark consonants from non consonants
Envelope and fine structure
speech in quiet and music
If speech transmission in quiet is primary goal of CIs, envelope seems most important to transmit.
If music is the goal, fine structure is also relevant
Sequential Stimulation vs. Paired Stimulation
SEQUENTIAL
- Sends electrical pulse to 1 electrode at a time sequentially
- (like playing piano with one hand/finger, only one key at at time)
- Slower rate (reduced pulses/sec)
PAIRED
- 2 electrodes stimulated at 1 time
- delivered to auditory nerve at faster rate
- (like playing piano with 2 hands)
Intensity is influenced by:
-how sound is captured
AND
-how sound is processed by the Cochlear implant system
Intensity and T-Mic2
- valuable cues about sound source and location
- improved speech understanding in noise
- natural use of most popular headsets
Intensity-
2 features of AutoSound
Dual-Action Automatic Gain Control (AGC)
•soft sounds remain audible, louder sounds loud but comfortable and not too loud
Wide Input Dynamic Range (IDR)
•access to softer elements preserved and compression is limited
•determines how much of sound captured by processor is mapped into recipient’s electrical dynamic range (EDR)- range between programmed thresholds (Ts) and comfort levels (Ms)
Intensity-
Advantages of AutoSound
- enables recipient to hear from whisper to shout without processor adjustments (access to sound in all environments automatically)
- Can go into variety of listening situations without worrying about missing out
- improved access to softer speech
- natural hearing for incidental learning and awareness of environment
- better hearing in challenging acoustic environments
Spectral-
Importance of Fine spectral resolution
Research suggests while 4-12 filter assignments are sufficient for speech, significantly more are required for understanding in noise and music.
- hearing in real (messy) world
- hearing in noise
- music appreciation
- environmental sounds
- tonal languages
Spectral-
Frequency bands
After sounds are captured, complex sound info is divided into frequency bands to be mapped across electrode array.
- CIs process essential same frequencies (250-8000 Hz)
- Processing within this range can be substantially different
-AB HiRes: 16 bands
CIS: 8 bands
-Cochlear ACE: 22 bands, but entire sections of spectral fingerprint of sounds are dropped
Spectral Resolution for Speech
Not as much resolution needed for speech understanding
- speech cues relatively robust in frequency domain
- even if formants are a little ‘sloppy’, vowels can still be distinguished
Spectral Resolution for Music
Difficult since targets are points, not ellipses in frequency space
- have to get much further away from original note to stimulate new area that assigns a new filter
- (2 notes close on piano would sound the same)
- (Why music not heard or appreciated as well as could be)
Spectral Resolution-
Fidelity 120
multiple independent current sources allow for steering of current between physical electrode contacts to deliver added spectral information (up to 120 unique pitch percepts)
- F120 aids with hearing in the real world, hearing in noise, music appreciation, hearing environmental sounds, and understanding tonal languages
- AB is only company that has implemented way to put current beyond physical electrode contacts; delivering current up to 7 unique pitch percepts between each electrode pair
Spectral Resolution-
HiRes Optima
- New compliance voltage 4V (versus 8V for F120)
- AutoVoltage FR management
- New default pulse width: APW II
- New current steering paradigm delivers stimulation ONLY between physical electrode contacts
- 53% improvement in battery life
- amount of current needed to produce intermediate pitch sensation is same as current delivered to single physical electrode; HOWEVER, lower current levels per physical electrode are needed to generate intermediate pitch sensations
ClearVoice
Sound processing strategy identifying channels where unwanted sound is present, and attenuates transmission in those channels to enhance the SNR
- Designed to improve listening in complex environments while maintaining same great performance in quiet
- Improve overall SNR, enhancing designed signal
- Particularly effective with steady-state sounds.
ClearVoice- available for use with which sound processors?
Harmony, Neptune, and Naída when used with CII or HiRes 90K
ClearVoice and modulated noise
Modulated noise- acoustic waveform with temporal modulations (multiple people talking)
- Modulated noise and reverberation- much like steady-state noise following reflections in a room
ClearVoice settings and maximum attenuations
low, medium, high
For a given setting, more attenuation is applied in a channel as the estimated SNR for that channel decreases
Maximum Attenuations
Low- 6 dB
Medium- 12 dB
High- 18 dB
Why use ClearVoice?
- significantly improves speech understanding in steady-state noise
- significantly improves speech understanding in multi-talker babble
- provides same great performance in quiet
- preferred by most subjects (93%) for everyday listening
- Almost all subjects benefit from ClearVoice (98%)
- All subjects (100%) like and would use ClearVoice.
M-Level
most comfortable loudness level
IDR
determines how much sound captured by the processor is mapped into recipient’s electrical dynamic range
