Interaural Level Differences and Sound Source Localization for Bilateral Cochlear Implant Patients

In this report, we used filtered noise bands to constrain listeners' access to interaural level differences (ILDs) and interaural time differences (ITDs) in a sound source localization task. The samples of interest were listeners with single-sided deafness (SSD) who had been fit with a cochlear implant in the deafened ear (SSD-CI). The comparison samples included listeners with normal hearing and bimodal hearing, i.e. with a cochlear implant in 1 ear and low-frequency acoustic hearing in the other ear. The results indicated that (i) sound source localization was better in the SSD-CI condition than in the SSD condition, (ii) SSD-CI patients rely on ILD cues for sound source localization, (iii) SSD-CI patients show functional localization abilities within 1-3 months after device activation and (iv) SSD-CI patients show better sound source localization than bimodal CI patients but, on average, poorer localization than normal-hearing listeners. One SSD-CI patient showed a level of localization within normal limits. We provide an account for the relative localization abilities of the groups by reference to the differences in access to ILD cues.

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Effects of Head Movements on Sound-Source Localization in Single-Sided Deaf Patients With Their Cochlear Implant On Versus Off

Ear & Hearing ◽

10.1097/aud.0000000000000882 ◽

2020 ◽

Vol 41 (6) ◽

pp. 1660-1674

Author(s):

M. Torben Pastore ◽

Sarah J. Natale ◽

Colton Clayton ◽

Michael F. Dorman ◽

William A. Yost ◽

...

Keyword(s):

Cochlear Implant ◽

Source Localization ◽

Sound Source ◽

Head Movements ◽

Sound Source Localization

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Sound Source Localization by Normal-Hearing Listeners, Hearing-Impaired Listeners and Cochlear Implant Listeners

Audiology and Neurotology ◽

10.1159/000444740 ◽

2016 ◽

Vol 21 (3) ◽

pp. 127-131 ◽

Cited By ~ 40

Author(s):

Michael F. Dorman ◽

Louise H. Loiselle ◽

Sarah J. Cook ◽

William A. Yost ◽

René H. Gifford

Keyword(s):

Cochlear Implant ◽

Source Localization ◽

Hearing Aids ◽

Sound Source ◽

Hearing Preservation ◽

Normal Hearing ◽

Hearing Impaired ◽

Sound Source Localization ◽

Localization Accuracy ◽

Rms Error

Objective: Our primary aim was to determine whether listeners in the following patient groups achieve localization accuracy within the 95th percentile of accuracy shown by younger or older normal-hearing (NH) listeners: (1) hearing impaired with bilateral hearing aids, (2) bimodal cochlear implant (CI), (3) bilateral CI, (4) hearing preservation CI, (5) single-sided deaf CI and (6) combined bilateral CI and bilateral hearing preservation. Design: The listeners included 57 young NH listeners, 12 older NH listeners, 17 listeners fit with hearing aids, 8 bimodal CI listeners, 32 bilateral CI listeners, 8 hearing preservation CI listeners, 13 single-sided deaf CI listeners and 3 listeners with bilateral CIs and bilateral hearing preservation. Sound source localization was assessed in a sound-deadened room with 13 loudspeakers arrayed in a 180-degree arc. Results: The root mean square (rms) error for the NH listeners was 6 degrees. The 95th percentile was 11 degrees. Nine of 16 listeners with bilateral hearing aids achieved scores within the 95th percentile of normal. Only 1 of 64 CI patients achieved a score within that range. Bimodal CI listeners scored at a level near chance, as did the listeners with a single CI or a single NH ear. Listeners with (1) bilateral CIs, (2) hearing preservation CIs, (3) single-sided deaf CIs and (4) both bilateral CIs and bilateral hearing preservation, all showed rms error scores within a similar range (mean scores between 20 and 30 degrees of error). Conclusion: Modern CIs do not restore a normal level of sound source localization for CI listeners with access to sound information from two ears.

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Sound source localization from tactile aids for unilateral cochlear implant users

The Journal of the Acoustical Society of America ◽

10.1121/1.4830825 ◽

2013 ◽

Vol 134 (5) ◽

pp. 4062-4062 ◽

Cited By ~ 2

Author(s):

Xuan Zhong ◽

Shuai Wang ◽

Michael Dorman ◽

William Yost

Keyword(s):

Cochlear Implant ◽

Source Localization ◽

Sound Source ◽

Sound Source Localization ◽

Tactile Aids

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Effects of Bilateral Automatic Gain Control Synchronization in Cochlear Implants With and Without Head Movements: Sound Source Localization in the Frontal Hemifield

Journal of Speech Language and Hearing Research ◽

10.1044/2021_jslhr-20-00493 ◽

2021 ◽

pp. 1-14

Author(s):

M. Torben Pastore ◽

Kathryn R. Pulling ◽

Chen Chen ◽

William A. Yost ◽

Michael F. Dorman

Keyword(s):

Source Localization ◽

Sound Source ◽

Automatic Gain Control ◽

Gain Control ◽

Broadband Noise ◽

Head Movements ◽

Sound Source Localization ◽

Sound Source Identification ◽

Interaural Difference ◽

Interaural Level Differences

Purpose For bilaterally implanted patients, the automatic gain control (AGC) in both left and right cochlear implant (CI) processors is usually neither linked nor synchronized. At high AGC compression ratios, this lack of coordination between the two processors can distort interaural level differences, the only useful interaural difference cue available to CI patients. This study assessed the improvement, if any, in the utility of interaural level differences for sound source localization in the frontal hemifield when AGCs were synchronized versus independent and when listeners were stationary versus allowed to move their heads. Method Sound source identification of broadband noise stimuli was tested for seven bilateral CI patients using 13 loudspeakers in the frontal hemifield, under conditions where AGCs were linked and unlinked. For half the conditions, patients remained stationary; in the other half, they were encouraged to rotate or reorient their heads within a range of approximately ± 30° during sound presentation. Results In general, those listeners who already localized reasonably well with independent AGCs gained the least from AGC synchronization, perhaps because there was less room for improvement. Those listeners who performed worst with independent AGCs gained the most from synchronization. All listeners performed as well or better with synchronization than without; however, intersubject variability was high. Head movements had little impact on the effectiveness of synchronization of AGCs. Conclusion Synchronization of AGCs offers one promising strategy for improving localization performance in the frontal hemifield for bilaterally implanted CI patients. Supplemental Material https://doi.org/10.23641/asha.14681412

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