Contralateral Interference Caused by Binaurally Presented Competing Speech in Adult Bilateral Cochlear-Implant Users.
Matthew J Goupell, Olga A Stakhovskaya, Joshua G W Bernstein
PMID 28787316WHAT IT FOUND
In nine adults with bilateral cochlear implants who had early deafness or asymmetric hearing histories, adding a competing talker to the other ear made speech understanding worse, not better.
Test both ears together in noise before assuming benefit.
Key findings
01When the competing talker was also sent to the ear opposite the target, speech understanding was substantially lower than when the target and competing talker were in the same ear.
02All nine listeners showed contralateral interference, meaning worse performance in the binaural condition than the monaural condition, in at least one ear.
03In the spatial task, average spatial release from masking was 1.6 dB, much smaller than the 4 to 6 dB often reported; it was 2.6 dB when the ear with the better signal-to-noise ratio was also the ear with better speech understanding, and 0.7 dB when it was the ear with poorer speech understanding.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The findings come from nine adults selected for hearing histories linked to poor binaural processing, so they do not show what happens for most bilateral cochlear implant users. The task used a closed-set sentence structure with very similar target and competing talkers, which may increase informational masking and may not match everyday conversation. The study did not include a matched comparison group of late-deafened, symmetrical users tested at the same time, so differences between groups cannot be treated as a controlled test of hearing history. Speech understanding in quiet varied widely, and some speech-reception thresholds were set to an arbitrary large value when listeners did not reach the halfway correct threshold. Self-reports that the target voice disappeared were anecdotal and were not measured as an outcome.
Declared interests
The article's conflict section states that financial disclosures and conflicts of interest are none.
The easy way to misread this
Do not conclude that a second cochlear implant will worsen speech for all bilateral users. This was a small lab study of nine adults selected for hearing histories linked to poor binaural processing, and it did not test everyday open-set conversation.