Sound Localization Bias and Error in Bimodal Listeners Improve Instantaneously When the Device Delay Mismatch Is Reduced.
Julian Angermeier, Werner Hemmert, Stefan Zirn
PMID 34057366WHAT IT FOUND
Hearing aid and cochlear implant users localized sounds more accurately immediately when the implant signal was delayed to reduce mismatch with their hearing aid.
Average error improved from 52.6 to 37.9 degrees, and the shift toward the implant was smaller.
Key findings
01Average localization rms error was 52.6 ± 11.4° before reducing the device delay mismatch and 37.9 ± 5.7° after reduction.
02The constant localization shift toward the cochlear implant averaged 25.2 ± 11.9° before reduction and 10.5 ± 8.2° after reduction.
03After 1 hour of familiarization, average rms error was 40.1 ± 8.3° and signed bias was 14.1 ± 11.9°, showing no further improvement.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
Nine participants is a small sample, and the study was done in a laboratory with noise bursts rather than everyday speech or environmental sounds. Participants had to use their hearing aid and implant every day and score above 50% on a monosyllabic word test, so it may not apply to people who do not meet those criteria. A participant completed only the initial tests because of a hardware malfunction. The best delay differed across participants, and the study did not show which delay would be best for routine care. The 1-hour familiarization period did not add further benefit, and the authors said it is unclear whether that period was sufficient. The work was funded by a cochlear implant manufacturer, and the tested delay line was custom-built.
Declared interests
The study was funded by MED-EL, a cochlear implant manufacturer, and the authors' institutions had received research grants from MED-EL.
The easy way to misread this
Do not conclude that routine cochlear implant or hearing aid settings should be changed to improve localization. The improvement came from a custom research delay line in nine participants tested with noise bursts, and a 1-hour familiarization period did not add further benefit.