1. Fang Du, Dr. Christina L. Runge, Dr. Yi Hu. April 21, 2018
Effect of High-Rate Pulse Trains on Speech Perception for Cochlear Implant Recipients
Fang Du, Dr. Christina L. Runge, Dr. Yi Hu.
April 21, 2018

2. Outline Introduction Problem Statement Design and Implementation
Testing and Data Analysis
Conclusion

3. Introduction What is cochlear implant(CI)
A cochlear implant is a device that provides a sense of sound to a person who is profoundly deaf or severely hard of hearing
The implant is surgically placed under the skin behind the ear
A cochlear implant has four major parts:
Microphones
Speech processor
Transmitter and receiver/stimulator
Electrodes
College of Imaging Arts & Sciences. (n.d.). Retrieved March 02, 2018, from

4. Introduction How cochlear implant works Normal Hearing/Hearing Aids
Acoustic
Electrical

5. Proposed Solution: Design a new stimulation strategy
Problem Statement
In Quiet
Improved sound processing strategies have helped many cochlear implant recipients regain satisfactory speech perception in quiet during the past three decades.
The average monosyllabic word score is nearly 80%
In Noise
Many signal processing techniques such as multiple-microphone noise-reduction and speech-enhancement methods have been developed to address this issue.
In general, they increase speech distortion as well as battery power consumption with limited benefits.
SOLVED
Proposed Solution: Design a new stimulation strategy
Srinivasan, A., Padilla, M., Shannon, R. and Landsberger, D. (2013). Improving speech perception in noise with current focusing in cochlear implant users. Hearing Research, 299, pp

6. Problem Statement Desynchronize neural response to electric signal
Poor speech perception
Poor electrode discrimination
Abnormally high synchrony in neural response
Loss of inner hair cell synapse
Desynchronize neural response
to electric signal
Limited dynamic range
Auditory nerves cannot process spontaneous activity
Runge-Samuelson, C. L. (2009). Effects of high-rate pulse trains on electrode discrimination in cochlear implant users. Trends in amplification, 13(2),

7. Problem Statement Jay Rubinstein’s Model:
It has been shown that high-rate desynchronized pulse train (DPT) has produced psychophysical dynamic range increases as large as 17dB in human subject.
No results have been reported to show Rubinstein’s model improves cochlear implants receivers’ speech perception
Adding continuous, appropriate-level, high-rate desynchronized pulse train (DPT) stimuli facilitates the desynchronizing of the neural response and increases the dynamic range.
Hong, R. S., Rubinstein, J. T., Wehner, D., & Horn, D. (2003). Dynamic range enhancement for cochlear implants. Otology & neurotology, 24(4),

8. Strategy Design Speech signal High-rate desynchronize pulses
Regular Continues Interleaved Stimulation (CIS) strategy
CIS strategy with DPT pulse
(Jay Rubinstein’s Model)
Speech signal
High-rate desynchronize pulses
Litvak, L., Delgutte, B., & Eddington, D. (2001). Auditory nerve fiber responses to electric stimulation: modulated and unmodulated pulse trains. The Journal of the Acoustical Society of America, 110(1),

9. Strategy Design Proposed High-rate DPT Strategy
Stimulation Strategy without DPT

10. Strategy Implementation
Envelope Extraction
Bandpass filters
Compression

11. Strategy Implementation
Filter Bank
To separate the speech signal to different electrodes
FB was individually customized based on patients’ map(corner frequency). Each band is 6th-order Butterworth bandpass filter

12. Strategy Implementation
Envelope Extraction
To determine the amplitude of biphasic pulse delivered to electrode
Hilbert Transform was used to closely extract the overall shape of a sound

13. Strategy Implementation
Compression
To ensure the output to fit into the patient’s dynamic range of electrically evoked hearing
𝑌= MCL −THR × log⁡(1+𝑦×𝑐) log⁡(1+𝑐) +THR Y
Compression output y
Envelope extraction output
MCL
Most comfortable level
THR
Threshold level c
Patient maplaw

14. Strategy Implementation
Speech without DPT
Speech with DPT
Patient Information
Future Testing

15. Speech Perception Testing
Ten cochlear implants users participated up to now
IEEE sentences were processed in both quiet and 4-talker babble background noise (SNR +10dB)
Each testing compared CIS without DPT and with DPT given different level of conditioner(100, 200, 300, 400 CU)
Total testing conditions consists of 26 lists, and each list has ten sentences.

16. Speech Perception Testing
Subject #
Age at Implantation (years)
Age at test (years)
Length of CI Use (years)
Length of Deafness (years)
Etiology
Internal Device and Electrode
Strategy 1 56 59
3.0 3
Meniere
Concert FLEX28
FS4-p 2 71 76
5.0 41
Idiopathic progressive 65 69
4.0 27 4 57 62 5
Sonatati100 Standard 49 55
6.0 6
FSP 81 85 7 29
Idiopathic sudden 8 34
7.0
Sonatati100 Medium 9 64 25
Concert Standard 10 46
9.0 24
Genetic
Pulsarci100 FLEX24

17. Speech Perception Data Analysis

18. Speech Perception Data Analysis
Average improvement is about 30%

19. Speech Perception Data Analysis

20. Conclusion Developed a new CI stimulation strategy
Implemented a GUI-based code generator to create customized CIS stimuli
Conducted subject testing which showed significant improvement in speech perception in noise

21. Thank you!