Head Shadow, Squelch, and Summation Effects in Bilateral Users of the MED-EL COMBI 40/40+ Cochlear Implant

Schleich, P.; Nopp, Peter; D’Haese, Patrick

doi:10.1097/01.aud.0000130792.43315.97

Cited by 230 publications

(248 citation statements)

References 19 publications

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“…Although CIs were not originally designed for bilateral use (e.g., the processors are not synchronized across the two ears, which results in random ITDs), more and more people are becoming bilaterally implanted. Studies suggest that bilateral CI users can understand speech slightly better than unilateral CI users, especially in noise (e.g., Schleich et al, 2004;Litovsky et al, 2009).…”

Section: B Implications For Cochlear Implantsmentioning

confidence: 99%

The role of envelope statistics in detecting changes in interaural correlation

Goupell

2012

The Journal of the Acoustical Society of America

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The role of envelope statistics in binaural masking-level differences (BMLDs) and correlation change detection was investigated in normal-hearing listeners. Thresholds and just-noticeable differences (JNDs) were measured for different bandwidths and center frequencies (500, 2000, 4000, and 8000 Hz) using Gaussian noises (GNs) and low-fluctuation noises (LFNs). At a 500-Hz center frequency, GN NoSo thresholds were higher than, NoSp thresholds were lower than, and correlation change detection JNDs were the same as LFN thresholds and JNDs. At higher center frequencies, GN NoSp thresholds were the same or higher than LFN thresholds and GN correlation change detection JNDs were much smaller than LFN JNDs. Using a pulsed sine vocoder, a second experiment was performed to investigate if binaural adaptation might contribute to the difference in GN and LFN detection. There was no effect of pulse rate, thus providing no clear evidence that binaural adaptation plays a role in these tasks. Both a cross-correlation model and a model that utilized the fluctuations in the interaural differences could explain a majority of the variance in the LFN correlation change JNDs.

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Section: B Implications For Cochlear Implantsmentioning

confidence: 99%

The role of envelope statistics in detecting changes in interaural correlation

Goupell

2012

The Journal of the Acoustical Society of America

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“…As yet, this promise has been only incompletely realized. Current benefits in sound localization are based primarily on interaural level difference (ILD) cues (van Hoesel 2004;Seeber and Fastl 2008;Aronoff et al 2010) and improvements in speech understanding in noise largely result from attending to the ear with the best signal-to-noise ratio (van Hoesel and Tyler 2003;Schleich et al 2004;Litovsky et al 2006). Importantly, bilateral CI users receive minimal benefit from interaural time difference (ITD) cues (van Hoesel 2012), which provide the greatest benefit to normal-hearing listeners in everyday situations (Bronkhorst and Plomp 1992;Zurek 1992;Macpherson and Middlebrooks 2002).…”

Section: Introductionmentioning

confidence: 99%

Congenital and Prolonged Adult-Onset Deafness Cause Distinct Degradations in Neural ITD Coding with Bilateral Cochlear Implants

Hancock

Chung

Delgutte

2013

JARO

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Bilateral cochlear implant (CI) users perform poorly on tasks involving interaural time differences (ITD), which are critical for sound localization and speech reception in noise by normal-hearing listeners. ITD perception with bilateral CI is influenced by age at onset of deafness and duration of deafness. We previously showed that ITD coding in the auditory midbrain is degraded in congenitally deaf white cats (DWC) compared to acutely deafened cats (ADC) with normal auditory development (Hancock et al., J. Neurosci, 30:14068). To determine the relative importance of early onset of deafness and prolonged duration of deafness for abnormal ITD coding in DWC, we recorded from single units in the inferior colliculus of cats deafened as adults 6 months prior to experimentation (long-term deafened cats, LTDC) and compared neural ITD coding between the three deafness models. The incidence of ITD-sensitive neurons was similar in both groups with normal auditory development (LTDC and ADC), but significantly diminished in DWC. In contrast, both groups that experienced prolonged deafness (LTDC and DWC) had broad distributions of best ITDs around the midline, unlike the more focused distributions biased toward contralateral-leading ITDs present in both ADC and normalhearing animals. The lack of contralateral bias in LTDC and DWC results in reduced sensitivity to changes in ITD within the natural range. The finding that early onset of deafness more severely degrades neural ITD coding than prolonged duration of deafness argues for the importance of fitting deaf children with sound processors that provide reliable ITD cues at an early age.

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“…The Bbetter ear effectr efers to the fact that, when two talkers occupy different locations, attenuation by the listener's head will improve the signal-to-noise ratio (SNR) at one or the other ear. This cue is available to both NH and CI listeners (Litovsky et al 2004;Schleich et al 2004;van Hoesel and Tyler 2003). In addition, the presence of a signal from a different location than a masker can reduce the correlation between the rightear and left-ear acoustic signals.…”

Section: Introductionmentioning

confidence: 99%

Binaural Unmasking with Bilateral Cochlear Implants

Long

Carlyon

Litovsky

et al. 2006

JARO

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Nearly 100,000 deaf patients worldwide have had their hearing restored by a cochlear implant (CI) fitted to one ear. However, although many patients understand speech well in quiet, even the most successful experience difficulty in noisy situations. In contrast, normalhearing (NH) listeners achieve improved speech understanding in noise by processing the differences between the waveforms reaching the two ears. Here we show that a form of binaural processing can be achieved by patients fitted with an implant in each ear, leading to substantial improvements in signal detection in the presence of competing sounds. The stimulus in each ear consisted of a narrowband noise masker, to which a tonal signal was sometimes added; this mixture was half-wave rectified, lowpass-filtered, and then used to modulate a 1000-pps biphasic pulse train. All four CI users tested showed significantly better signal detection when the signal was presented out of phase at the two ears than when it was in phase. This advantage occurred even though subjects only received information about the slowly varying sound envelope to be presented, contrary to previous reports that waveform fine structure dominates binaural processing. If this advantage generalizes to multichannel situations, it would demonstrate that envelope-based CI speech-processing strategies may allow patients to exploit binaural unmasking in order to improve speech understanding in noise. Furthermore, because the tested patients had been deprived of binaural hearing for eight or more years, our results show that some sensitivity to time-varying interaural cues can persist over extended periods of binaural deprivation.

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Head Shadow, Squelch, and Summation Effects in Bilateral Users of the MED-EL COMBI 40/40+ Cochlear Implant

Cited by 230 publications

References 19 publications

The role of envelope statistics in detecting changes in interaural correlation

The role of envelope statistics in detecting changes in interaural correlation

Congenital and Prolonged Adult-Onset Deafness Cause Distinct Degradations in Neural ITD Coding with Bilateral Cochlear Implants

Binaural Unmasking with Bilateral Cochlear Implants

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