Mechanisms of Localization and Speech Perception with Colocated and Spatially Separated Noise and Speech Maskers Under Single-Sided Deafness with a Cochlear Implant.
Coral Dirks, Peggy B Nelson, Douglas P Sladen and 1 others
PMID 30870240WHAT IT FOUND
A cochlear implant improved sound localization only when high-frequency level differences were available, not when timing cues were required.
For speech in noise, the implant provided a significant benefit only when a two-talker babble masker was on the hearing-ear side, likely due to improved signal levels rather than restored binaural hearing.
Key findings
01Localization errors decreased significantly with the CI only for high-frequency tones that provide interaural level differences, while low-frequency tones relying on timing cues showed no improvement.
02Speech recognition in noise did not improve with the CI when target and masker were co-located, but did improve significantly when a two-talker babble masker was presented to the acoustic-hearing side.
03The benefit in speech perception appeared to stem from the head-shadow effect improving the signal-to-noise ratio at the CI ear, rather than from restored binaural masking release.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The sample size was very small (5 in Experiment 1, 8 in Experiment 2), limiting the generalizability of the findings. One participant in Experiment 2 had significant hearing loss in the acoustic ear and used a hearing aid, technically making them bimodal rather than having pure SSD. The vocoder simulation in normal-hearing listeners did not perfectly predict the performance of actual SSD+CI listeners. The study did not test long-term adaptation effects, as it focused on acute performance with the CI on versus off.
Declared interests
None reported in the provided text.
The easy way to misread this
Do not assume the CI restores binaural hearing or masking release. The significant speech benefit occurred only in a specific spatial configuration (babble on the acoustic side) and is attributed to the head-shadow effect improving the signal-to-noise ratio at the CI ear, not to true binaural integration.