Bilateral Versus Unilateral Cochlear Implantation in Adult Listeners: Speech-On-Speech Masking and Multitalker Localization.
Baljeet Rana, Jörg M Buchholz, Catherine Morgan and 5 others
PMID 28752811WHAT IT FOUND
A second cochlear implant improved speech understanding when both distractors came from one side, by 7.5 dB on average.
When distractors were on both sides, the 3 dB average benefit was not significant. Localization error improved by 27 degrees.
Key findings
01A second cochlear implant improved speech-in-noise thresholds by 7.5 dB on average when both distractors came from one side.
02When distractors were on both sides, the average bilateral speech benefit was 3 dB and not significant.
03A second implant improved horizontal localization error by 27 degrees on average, with individual gains from 9 to 68 degrees.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
Only seven adults were recruited, and one was excluded from speech comprehension analysis because of fatigue. Participants were experienced bilateral CI users who scored more than 60% on a sentence test at +10 dB SNR, so results may not apply to newer or poorer performers. Adaptive noise suppression and directional features were turned off during testing, so everyday processor settings may change performance. The tasks used short questions and 15-second speech segments in a loudspeaker array, not real rooms with reverberation and multiple moving talkers. Localization benefited from long speech segments and wide loudspeaker spacing, which may make real-world performance look better than it is.
Declared interests
The metadata lists non-U.S. government research support. The supplied text does not include a conflicts-of-interest statement. It notes that all participants used Cochlear Limited devices and travelled from Japan to Sydney for testing.
The easy way to misread this
Do not conclude that bilateral cochlear implants reliably improve speech understanding when talkers are on both sides. The average 3 dB benefit in that condition was not significant, and individual benefits varied from 0 to 7 dB.