PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Coding of Electrical Stimulation Patterns for Binaural Signal
Processing in Cochlear Implants
Waldo Nogueira1; Tom Gajecki1; Reemt Hinrichs2; Joern Ostermann2
1 Department of Otolaryngology, Medical University Hannover, Karl-Wiechert-Allee 3, 30625 Hannover
2 Institut fuer Informationsverarbeitung, Leibniz Universitaet Hannover, Appelstraße 9a, 30167 Hannover

ABSTRACT
Binaural sound coding strategies can improve speech intelligibility for cochlear implant (CI) users. Bilateralcochlear implant (BiCI) users do not benefit as much as NH listeners from binaural hearing. We hypothesizethat these limitations arise from the fact that implants do not provide the electrical stimulus at the same time(i.e. synchronized electrical stimulation), but also, when using N-of-M type sound coding strategies, theselected bands used to stimulate in each of the sides will in general differ, limiting the access to binaural cues.
In the first part of this work, we investigate the effect of bilaterally synchronized electrical stimulation
on BiCI users in speech perception tasks in a better-signal-to-noise-ratio ear (better-SNR ear) listening
scenario [1]. We also propose a Binaural N-of-M (BINOM) sound coding strategy to improve the SNR of themasked ear. The effect of synchronous bilateral stimulation and BINOM is assessed by means ofspeech-in-noise intelligibility tests. Furthermore, the effect of adding a worse- SNR side is measured by also
performing monaural speech in- noise intelligibility tests with each listening side. Finally, speech
performance is assessed by selecting the bands that would be selected if no noise was present (ideal bandselection). The outcome of this work shows that in a better-SNR binaural listening scenario, bilaterally
synchronized stimulation besides the sharing of band selection information provided by the favorable hearing
side with the contralateral ear leads to an improvement in speech intelligibility in BiCI users.
In the second part of this work we investigate an audio compression algorithm to transmit the signals
from one processor to another as binaural sound coding strategies require a signal transmission between thetwo CIs [2]. As power consumption needs to be low in CIs, efficient coding of the signals is necessary. In thiswork it is proposed to code the excitation patterns (EP) of the CI instead of the audio signals captured by themicrophones. For this purpose, a differential pulse code modulation codec with zero algorithmic delay tocode the EP of the BINOM sound coding strategy is presented. The EP codec was compared to standardized
speech codecs using the SNR as well as speech intelligibility and quality measures in bilateral CI users.

ACKNOWLEDGEMENTS
This work was funded by the Deutsche Forschungsgemeinschaft (DFG, German ResearchFoundation) under Germany's Excellence Strategy – EXC 2177/1 - Project ID 381895691 and fundedby the German Research Foundation (DFG) - Project number: 396932747 (PIs: W. Nogueira; J.
Ostermann).

REFERENCES[1] T. Gajecki, W. Nogueira (2018), A Synchronized Binaural N-of-M Sound Coding Strategy for Bilateral
Cochlear Implant Users, ITG Speech Communication, Oldenburg, Germany.
[2] R. Hinrichs, T. Gajecki, J. Ostermann, W. Nogueira (2019), Coding of Electrical Stimulation Patternsfor Binaural Sound Coding Strategies for Cochlear Implants, IEEE Engineering in Medicine andBiology Conference, Berlin, Germany, July.

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Nogueiravaquez.waldo@mh-hannover.de2235