The effect of manipulating interaural level differences on lateralization by bilateral cochlear implant users

2015 ◽  
Vol 137 (4) ◽  
pp. 2321-2321
Author(s):  
Christopher A. Brown
Keyword(s):  
Cochlear Implant ◽  
Bilateral Cochlear Implant ◽  
Interaural Level Differences

scholarly journals Head Shadow, Summation, and Squelch in Bilateral Cochlear-Implant Users With Linked Automatic Gain Controls

2021 ◽  
Vol 25 ◽  
pp. 233121652110181
Author(s):  
Taylor A. Bakal ◽  
Kristina DeRoy Milvae ◽  
Chen Chen ◽  
Matthew J. Goupell
Keyword(s):  
Cochlear Implant ◽  
Functional Performance ◽  
Binaural Hearing ◽  
Normal Hearing ◽  
Functional Asymmetry ◽  
Speech Understanding ◽  
Speech Understanding In Noise ◽  
Bilateral Cochlear Implant ◽  
Automatic Gain Controls ◽  
Interaural Level Differences

Speech understanding in noise is poorer in bilateral cochlear-implant (BICI) users compared to normal-hearing counterparts. Independent automatic gain controls (AGCs) may contribute to this because adjusting processor gain independently can reduce interaural level differences that BICI listeners rely on for bilateral benefits. Bilaterally linked AGCs may improve bilateral benefits by increasing the magnitude of interaural level differences. The effects of linked AGCs on bilateral benefits (summation, head shadow, and squelch) were measured in nine BICI users. Speech understanding for a target talker at 0° masked by a single talker at 0°, 90°, or −90° azimuth was assessed under headphones with sentences at five target-to-masker ratios. Research processors were used to manipulate AGC type (independent or linked) and test ear (left, right, or both). Sentence recall was measured in quiet to quantify individual interaural asymmetry in functional performance. The results showed that AGC type did not significantly change performance or bilateral benefits. Interaural functional asymmetries, however, interacted with ear such that greater summation and squelch benefit occurred when there was larger functional asymmetry, and interacted with interferer location such that smaller head shadow benefit occurred when there was larger functional asymmetry. The larger benefits for those with larger asymmetry were driven by improvements from adding a better-performing ear, rather than a true binaural-hearing benefit. In summary, linked AGCs did not significantly change bilateral benefits in cases of speech-on-speech masking with a single-talker masker, but there was also no strong detriment across a range of target-to-masker ratios, within a small and diverse BICI listener population.

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

2021 ◽  
Author(s):  
Alan Archer-Boyd ◽  
Robert P. Carlyon
Keyword(s):  
Cochlear Implant ◽  
Head Movement ◽  
Automatic Gain Control ◽  
Gain Control ◽  
Release Time ◽  
Dynamic Changes ◽  
Bilateral Cochlear Implant ◽  
Interaural Level Differences ◽  
Range Of Values ◽  
Channel Systems

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.

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

2014 ◽  
Vol 35 (6) ◽  
pp. 633-640 ◽  
Author(s):  
Michael F. Dorman ◽  
Louise Loiselle ◽  
Josh Stohl ◽  
William A. Yost ◽  
Anthony Spahr ◽  
...  
Keyword(s):  
Cochlear Implant ◽  
Source Localization ◽  
Sound Source ◽  
Sound Source Localization ◽  
Bilateral Cochlear Implant ◽  
Interaural Level Differences

scholarly journals Improving Localization and Speech Reception in Noise for Bilateral Cochlear Implant Recipients

2019 ◽  
Vol 23 ◽  
pp. 233121651983149 ◽  
Author(s):  
Wendy B. Potts ◽  
Lakshmish Ramanna ◽  
Trevor Perry ◽  
Christopher J. Long
Keyword(s):  
Cochlear Implant ◽  
Automatic Gain Control ◽  
Gain Control ◽  
Interaural Level Difference ◽  
Mean Square ◽  
Localization Accuracy ◽  
Speech In Noise ◽  
Speech Reception ◽  
Bilateral Cochlear Implant ◽  
Comparative Survey

This study looked at different methods to preserve interaural level difference (ILD) cues for bilateral cochlear implant (BiCI) recipients. One possible distortion to ILD is from automatic gain control (AGC). Localization accuracy of BiCI recipients using default versus increased AGC threshold and linked AGCs versus independent AGCs was examined. In addition, speech reception in noise was assessed using linked versus independent AGCs and enabling and disabling Autosensitivity™ Control. Subjective information via a diary and questionnaire was also collected about maps with linked and independent AGCs during a take-home experience. Localization accuracy improved in the increased AGC threshold and the linked AGCs conditions. Increasing the AGC threshold resulted in a 4° improvement in root mean square error averaged across all speaker locations. Using linked AGCs, BiCI participants experienced an 8° improvement for all speaker locations and a 19° improvement at the speaker location most affected by the AGC. Speech reception threshold in noise improved by an average of 2.5 dB when using linked AGCs versus independent AGCs. In addition, the effect of linked AGCs on speech in noise was compared with that of Autosensitivity™ Control. The Speech, Spatial, and Qualities of Hearing Scale-12 question comparative survey showed an improvement when using maps with linked AGCs. These findings support the hypothesis that ILD cues may be preserved by increasing the AGC threshold or linking AGCs.

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