Localization in Reverberation with Cochlear Implants

Abstract

Users of bilateral cochlear implants (CIs) experience difficulties localizing sounds in reverberant rooms, even in rooms where normal-hearing listeners would hardly notice the reverberation. We measured the localization ability of seven bilateral CI users listening with their own devices in anechoic space and in a simulated reverberant room. To determine factors affecting performance in reverberant space we measured the sensitivity to interaural time differences (ITDs), interaural level differences (ILDs), and forward masking in the same participants using direct computer control of the electric stimulation in their CIs. Localization performance, quantified by the coefficient of determination r2 and the root mean squared error, was significantly worse in the reverberant room than in anechoic conditions. Localization performance in the anechoic room, expressed as r2, was best predicted by subject’s sensitivity to ILDs. However, the decrease in localization performance caused by reverberation was better predicted by the sensitivity to envelope ITDs measured on single electrode pairs, with a correlation coefficient of 0.92. The CI users who were highly sensitive to envelope ITDs also better maintained their localization ability in reverberant space. Results in the forward masking task added only marginally to the predictions of localization performance in both environments. The results indicate that envelope ITDs provided by CI processors support localization in reverberant space. Thus, methods that improve perceptual access to envelope ITDs could help improve localization with bilateral CIs in everyday listening situations.

Using ILD or ITD Cues for Sound Source Localization and Speech Understanding in a Complex Listening Environment by Listeners With Bilateral and With Hearing-Preservation Cochlear Implants

“…Only two of the six listeners had better-than-chance performance using ITD cues. Kerber and Seeber (2013) used direct streaming of the stimulus to pitch-matched electrodes on a localization task. All seven subjects lateralized using ILD cues.…”

Evidence for a neural source of the precedence effect in sound localization

“…Brown and Stecker 2013). Recently, Kerber and Seeber (2013) demonstrated particularly poor localization accuracy among CI users wearing their clinical processors in a simulated reverberant environment (relative to anechoic conditions), suggestive of a weak PE, although the PE per se was not directly assessed. Interestingly, the deleterious effect of reverberation on localization appeared to be related to ITD sensitivity: Subjects with better ITD sensitivity tended to be less affected by reverberation, which would be consistent with a relatively more intact PE in those subjects.…”

“…It remains unclear whether CI users who are insensitive to ITD (particularly congenitally or early-deaf individuals; Litovsky et al 2010) are able to experience a PE, e.g., via ILD sensitivity (see Brown et al 2015;Litovsky et al 1999). Work by Kerber and Seeber (2013) demonstrated that better ITD sensitivity was associated with better localization in reverberation for CI users wearing their clinical speech processors. To this end, future work evaluating the PE in users of bilateral CIs with a more realistic stimulation protocol (e.g., multielectrode) and more extensive stimulus battery, perhaps including speech, will further elucidate the extent to which CI users may obtain clinical benefit from the PE.…”

“…Subjects were adult users of bilateral cochlear implants (CIs), auditory prosthetic devices that bypass the inner ear to stimulate auditory nerve fibers directly with electrical impulses (for review see Wilson and Dorman 2008). One report (Kerber and Seeber 2013) suggested that bilateral CI users with relatively good ITD sensitivity were able to localize sound sources in a simulated reverberant environment nearly as well as in an anechoic environment, suggesting that the PE might be functional in at least some CI users (see also Agrawal 2008;van Hoesel 2007). We report that, given appropriate stimulation, bilateral CI subjects with ITD sensitivity exhibited aspects of the PE similar to normal-hearing (NH) listeners, suggesting that neural mechanisms are sufficient to produce the PE and moreover that provision of ITD information may restore perceptual benefits of the PE among some individuals in this growing clinical population.…”

Objective analysis of ambisonics for hearing aid applications: Effect of listener's head, room reverberation, and directional microphones

“…Using a loudspeaker-based virtual sound environment (VSE) to create a realistic three-dimensional (3D) audio scene appears to be a more flexible candidate for listening tests with HAs (Minnaar et al, 2010). The "Simulated Open-Field Environment" system (Seeber et al, 2010;Kerber and Seeber, 2013) and the sound reproduction system described by Favrot and Buchholz (2010), for example, have been such attempts to induce realism into laboratory testing. Loudspeaker-based VSEs can be generated either by acoustically simulating or by recording a given environment and then decoding the scene information to appropriate loudspeaker signals.…”