Searching for the Sound of a Cochlear Implant: Evaluation of Different Vocoder Parameters by Cochlear Implant Users With Single-Sided Deafness.
Chadlia Karoui, Chris James, Pascal Barone and 3 others
PMID 31533581WHAT IT FOUND
Cochlear implant users judged a pulsatile vocoder carrier closer to their implant sound than sinusoidal or noise carriers.
They also preferred lower frequency mismatch, but the simulations still sounded different from the real implant.
Key findings
01The pulse spreading harmonic complex carrier was preferred over sinusoidal and noise carriers, while sinusoidal and noise carriers did not differ.
02No-mismatch and 2-ERB mismatch vocoders were not distinguished, and each was preferred over 4-ERB mismatch.
03Only one participant showed full adaptation to the implant frequency allocation table, two showed partial adaptation, and six were inconclusive.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study involved a small group of French-speaking cochlear implant users with near-normal hearing in the other ear, so the results may not generalise to broader implant populations. Participants judged short speech sounds in a laboratory task, not everyday listening, implant outcomes, or speech rehabilitation results. The vocoder simulations used fewer channels than real implants and did not match all implant signal processing strategies. Only a small set of speech sentences was used, so the preference for a carrier may not hold for other sounds. Individual responses varied widely, and CT analysis suggested that larger and inconsistent frequency mismatches were associated with less clear adaptation. The authors stated that the simulations remained qualitatively different from the implant sound, so no vocoder was shown to reproduce it exactly.
The easy way to misread this
Do not conclude that the pulse spreading harmonic complex carrier is a clinically validated replacement for implant sound or that cochlear implant users can adapt to large frequency mismatches. This was a laboratory evaluation with limited participants, and the simulations still differed from the real implant sound.