The use of interaural time and level difference cues by bilateral cochlear implant users

Self Cite

Bilateral cochlear implant users often have difficulty fusing sounds from the two ears into a single percept. However, measuring fusion can be difficult, particularly with cochlear implant users who may have no reference for a fully fused percept. As a first step to address this, this study examined how localization performance of normal hearing subjects relates to binaural fusion. The stimuli were vocoded speech tokens with various interaural mismatches. The results reveal that the percentage of stimuli perceived as fused was correlated with localization performance, suggesting that changes in localization performance can serve as an indicator for binaural fusion changes.

Section: Discussionmentioning

confidence: 99%

“…For example, Nopp et al (2004), Aronoff et al (2010), and Majdak et al (2011) found RMS errors of 29…”

Section: Discussionmentioning

confidence: 99%

Localization performance correlates with binaural fusion for interaurally mismatched vocoded speech

Suneel¹,

Staisloff²,

Shayman³

et al. 2017

Self Cite

“…However, because so little is known about ILD sensitivity with any of these stimuli, further research is required. In particular, because CIs transmit ILDs better than ITDs (van Hoesel, 2004;Aronoff et al, 2010;Litovsky et al, 2012) children with CIs may show better ILD than ITD sensitivity, in which case future research should explore the importance of envelope shape for ILD sensitivity. Another possibility is that the difference between GET and transposed for ILD stimuli was due to an order effect because GET was always tested before the transposed tone stimuli.…”

Section: Discussionmentioning

confidence: 99%

Binaural hearing in children using Gaussian enveloped and transposed tones

Ehlers

Kan

Winn

et al. 2016

Children who use bilateral cochlear implants (BiCIs) show significantly poorer sound localization skills than their normal hearing (NH) peers. This difference has been attributed, in part, to the fact that cochlear implants (CIs) do not faithfully transmit interaural time differences (ITDs) and interaural level differences (ILDs), which are known to be important cues for sound localization. Interestingly, little is known about binaural sensitivity in NH children, in particular, with stimuli that constrain acoustic cues in a manner representative of CI processing. In order to better understand and evaluate binaural hearing in children with BiCIs, the authors first undertook a study on binaural sensitivity in NH children ages 8-10, and in adults. Experiments evaluated sound discrimination and lateralization using ITD and ILD cues, for stimuli with robust envelope cues, but poor representation of temporal fine structure. Stimuli were spondaic words, Gaussian-enveloped tone pulse trains (100 pulse-per-second), and transposed tones. Results showed that discrimination thresholds in children were adult-like (15-389 ls for ITDs and 0.5-6.0 dB for ILDs). However, lateralization based on the same binaural cues showed higher variability than seen in adults. Results are discussed in the context of factors that may be responsible for poor representation of binaural cues in bilaterally implanted children.

“…In Grantham et al (2007), CI users showed a significant increase in free-field localization error for low-pass filtered noise compared to wide-band noise but no difference in performance for highpass noise compared to wide-band noise, suggesting that localization of noise bursts is primarily based on highfrequency ILDs and not low-frequency ITDs. Aronoff et al (2010) used VAS techniques to determine the relative contribution of ITD and ILD to sound localization in CI users. By modifying head-related transfer functions to present stimuli that varied in ITDs or ILDs separately, they found that when ITDs were varied and ILDs held constant, sound localization performance was significantly poorer compared to free-field localization.…”

Section: Introductionmentioning

confidence: 99%

Effect of mismatched place-of-stimulation on binaural fusion and lateralization in bilateral cochlear-implant users

Kan¹,

Stoelb²,

Litovsky³

et al. 2013

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245

Bilateral cochlear implants (CIs) have provided some success in improving spatial hearing abilities to patients, but with large variability in performance. One reason for the variability is that there may be a mismatch in the place-of-stimulation arising from electrode arrays being inserted at different depths in each cochlea. Goupell et al. [(2013b). J. Acoust. Soc. Am. 133(4), [2272][2273][2274][2275][2276][2277][2278][2279][2280][2281][2282][2283][2284][2285][2286][2287] showed that increasing interaural mismatch led to non-fused auditory images and poor lateralization of interaural time differences in normal hearing subjects listening to a vocoder. However, a greater bandwidth of activation helped mitigate these effects. In the present study, the same experiments were conducted in post-lingually deafened bilateral CI users with deliberate and controlled interaural mismatch of single electrode pairs. Results show that lateralization was still possible with up to 3 mm of interaural mismatch, even when off-center, or multiple, auditory images were perceived. However, mismatched inputs are not ideal since it leads to a distorted auditory spatial map. Comparison of CI and normal hearing listeners showed that the CI data were best modeled by a vocoder using Gaussian-pulsed tones with 1.5 mm bandwidth. These results suggest that interaural matching of electrodes is important for binaural cues to be maximally effective.