Williges, Ben and Jürgens, Tim and Hu, Hongmei and Dietz, Mathias (2018) Coherent coding of enhanced interaural cues improves sound localization in noise with bilateral cochlear implants. Trends in hearing, 22. p. 233121651878174. ISSN 2331-2165

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Abstract

Bilateral cochlear implant (BCI) users only have very limited spatial hearing abilities. Speech coding strategies transmit interaural level differences (ILDs) but in a distorted manner. Interaural time difference (ITD) information transmission is even more limited. With these cues, most BCI users can coarsely localize a single source in quiet, but performance quickly declines in the presence of other sound. This proof-of-concept study presents a novel signal processing algorithm specific for BCIs, with the aim to improve sound localization in noise. The core part of the BCI algorithm duplicates a monophonic electrode pulse pattern and applies quasistationary natural or artificial ITDs or ILDs based on the estimated direction of the dominant source. Three experiments were conducted to evaluate different algorithm variants: Experiment 1 tested if ITD transmission alone enables BCI subjects to lateralize speech. Results showed that six out of nine BCI subjects were able to lateralize intelligible speech in quiet solely based on ITDs. Experiments 2 and 3 assessed azimuthal angle discrimination in noise with natural or modified ILDs and ITDs. Angle discrimination for frontal locations was possible with all variants, including the pure ITD case, but for lateral reference angles, it was only possible with a linearized ILD mapping. Speech intelligibility in noise, limitations, and challenges of this interaural cue transmission approach are discussed alongside suggestions for modifying and further improving the BCI algorithm.

Item Type:	Article
Additional Information:	Publiziert mit Hilfe des DFG-geförderten Open Access-Publikationsfonds der Carl von Ossietzky Universität Oldenburg.
Uncontrolled Keywords:	cochlear implants, localization, lateralization, binaural cues
Subjects:	Science and mathematics > Physics Technology, medicine, applied sciences > Medicine and health
Divisions:	Faculty of Medicine and Health Sciences > Department of Medical Physics and Acoustics
Date Deposited:	12 Sep 2019 12:25
Last Modified:	13 Sep 2019 07:05
URI:	https://oops.uni-oldenburg.de/id/eprint/4170
URN:	urn:nbn:de:gbv:715-oops-42517
DOI:	doi:10.1177/2331216518781746
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