Lateralization of virtual sound sources with a binaural cochlear-implant sound coding strategy inspired by the medial olivocochlear reflex

Lopez‐Poveda, Enrique A.; Eustaquio-Martín, Almudena; Fumero, Milagros J.; Stohl, Joshua S.; Schatzer, Reinhold; Nopp, Peter; Wolford, Robert D.; Gorospe, José Miguel Correa; Polo, Rubén; Revilla, Auxiliadora Gutiérrez; Wilson, Blake S.

doi:10.1016/j.heares.2019.05.004

Cited by 21 publications

(14 citation statements)

References 43 publications

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“…Apart from improved speech understanding in noise ( 1 – 5 ), sound localization performance in the bilateral CI condition also improved when compared to unilateral CI [e.g., ( 1 , 5 , 6 )]. However, the benefit of bilateral implantation is not equivalent to binaural hearing, and the performance gap between bilateral CI vs. normal-hearing (NH) listeners is still significant ( 7 , 8 ). Normal-hearing listeners localize sounds in azimuth with high acuity and precision, thanks to the efficient processing of interaural level differences (ILDs) and interaural timing differences (ITDs).…”

Section: Introductionmentioning

confidence: 99%

Spatial Hearing by Bilateral Cochlear Implant Users With Temporal Fine-Structure Processing

et al. 2020

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Several studies have demonstrated the advantages of the bilateral vs. unilateral cochlear implantation in listeners with bilateral severe to profound hearing loss. However, it remains unclear to what extent bilaterally implanted listeners have access to binaural cues, e.g., accurate processing of interaural timing differences (ITDs) for low-frequency sounds (<1.5 kHz) and interaural level differences (ILDs) for high frequencies (>3 kHz). We tested 25 adult listeners, bilaterally implanted with MED-EL cochlear implant (CI) devices, with and without fine-structure (FS) temporal processing as encoding strategy in the low-frequency channels. In order to assess whether the ability to process binaural cues was affected by fine-structure processing, we performed psychophysical ILD and ITD sensitivity measurements and free-field sound localization experiments. We compared the results of the bilaterally implanted listeners with different numbers of FS channels. All CI listeners demonstrated good sensitivity to ILDs, but relatively poor to ITD cues. Although there was a large variability in performance, some bilateral CI users showed remarkably good localization skills. The FS coding strategy for bilateral CI hearing did not improve fine-structure ITD processing for spatial hearing on a group level. However, some CI listeners were able to exploit weakly informative temporal cues to improve their low-frequency spatial perception.

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Section: Introductionmentioning

confidence: 99%

Spatial Hearing by Bilateral Cochlear Implant Users With Temporal Fine-Structure Processing

et al. 2020

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“…In addition, more advanced forms of linked AGC available in the literature (but not clinically), have not been considered. These include a linked medial olivocochlear-inspired system (Lopez-Poveda et al, 2019;Lopez-Poveda et al, 2020), the linked single-channel system used by Potts et al (2019), and the linked and multichannel system by Spencer et al (2019). In all cases, speech intelligibility was improved for some sets of parameters, as was localization with a stationary listener and source where tested.…”

Section: Future Work and Limitationsmentioning

confidence: 99%

Further simulations of the effect of cochlear-implant pre-processing and head movement on interaural level differences

Archer-Boyd¹,

Carlyon²

2021

Preprint

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We simulated the effect of several automatic gain control (AGC) and AGC-like systems and head movement on the output levels, and resulting interaural level differences (ILDs) produced by bilateral cochlear-implant (CI) processors. The simulated AGC systems included unlinked AGCs with a range of parameter settings, linked AGCs, and two proprietary multi-channel systems used in contemporary CIs. The results show that over the range of values used clinically, the parameters that most strongly affect dynamic ILDs are the release time and compression ratio. Linking AGCs preserves ILDs at the expense of monaural level changes and, possibly, comfortable listening level. Multichannel AGCs can whiten output spectra, and/or distort the dynamic changes in ILD that occur during and after head movement. We propose that an unlinked compressor with a ratio of approximately 3:1 and a release time of 300-500 ms can preserve the shape of dynamic ILDs, without causing large spectral distortions or sacrificing listening comfort.

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“…In BiCI listeners, the benefit of synchronized AGC is more clear, because, as noted earlier, they rely almost entirely on ILDs for spatial hearing abilities. In these listeners, synchronized AGC has been shown to provide improvements in both localization abilities and speech reception threshold (SRT; Lopez-Poveda et al., 2019 ; Potts et al., 2019 ). Improved speech recognition with synchronized AGC has also been observed in spatially separated speech and noise for NH adults ( Wiggins & Seeber, 2013 ), in BiCI simulation ( Spencer et al., 2020 ) and in adults with BiCIs ( Lopez-Poveda et al., 2017 ; Potts et al., 2019 ).…”

Section: Introductionmentioning

confidence: 99%

Synchronized Automatic Gain Control in Bilateral Cochlear Implant Recipients Yields Significant Benefit in Static and Dynamic Listening Conditions

Dwyer

Chen²,

Hehrmann³

et al. 2021

Trends in Hearing

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Individuals with bilateral cochlear implants (BiCIs) rely mostly on interaural level difference (ILD) cues to localize stationary sounds in the horizontal plane. Independent automatic gain control (AGC) in each device can distort this cue, resulting in poorer localization of stationary sound sources. However, little is known about how BiCI listeners perceive sound in motion. In this study, 12 BiCI listeners’ spatial hearing abilities were assessed for both static and dynamic listening conditions when the sound processors were synchronized by applying the same compression gain to both devices as a means to better preserve the original ILD cues. Stimuli consisted of band-pass filtered (100–8000 Hz) Gaussian noise presented at various locations or panned over an array of loudspeakers. In the static listening condition, the distance between two sequentially presented stimuli was adaptively varied to arrive at the minimum audible angle, the smallest spatial separation at which the listener can correctly determine whether the second sound was to the left or right of the first. In the dynamic listening condition, participants identified if a single stimulus moved to the left or to the right. Velocity was held constant and the distance the stimulus traveled was adjusted using an adaptive procedure to determine the minimum audible movement angle. Median minimum audible angle decreased from 17.1° to 15.3° with the AGC synchronized. Median minimum audible movement angle decreased from 100° to 25.5°. These findings were statistically significant and support the hypothesis that synchronizing the AGC better preserves ILD cues and results in improved spatial hearing abilities. However, restoration of the ILD cue alone was not enough to bridge the large performance gap between BiCI listeners and normal-hearing listeners on these static and dynamic spatial hearing measures.

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Lateralization of virtual sound sources with a binaural cochlear-implant sound coding strategy inspired by the medial olivocochlear reflex

Cited by 21 publications

References 43 publications

Spatial Hearing by Bilateral Cochlear Implant Users With Temporal Fine-Structure Processing

Spatial Hearing by Bilateral Cochlear Implant Users With Temporal Fine-Structure Processing

Further simulations of the effect of cochlear-implant pre-processing and head movement on interaural level differences

Synchronized Automatic Gain Control in Bilateral Cochlear Implant Recipients Yields Significant Benefit in Static and Dynamic Listening Conditions

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