Head Shadow, Summation, and Squelch in Bilateral Cochlear-Implant Users With Linked Automatic Gain Controls.
Taylor A Bakal, Kristina DeRoy Milvae, Chen Chen and 1 others
PMID 34057387WHAT IT FOUND
Linking the automatic gain controls on both cochlear implant processors made no difference to speech understanding in noise for nine bilateral users.
The linked settings did not improve performance, but they also did not cause any harm or make understanding worse.
Key findings
01Speech understanding with linked AGCs was not significantly different from independent AGCs across all tested conditions.
02More asymmetrical listeners showed larger apparent summation and squelch benefits, which the authors attribute to the monaural contribution of the better ear rather than true binaural processing.
03The linked technology did not result in any performance detriments for the listeners.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
Read the rest of this summary
You get three full summaries a month, free, and we do not ask for a card. Search, the TL;DRs and your library stay unlimited either way.
What it does not show
The sample was very small, with only nine participants. The study used a single-talker masker; previous research suggests linked AGCs may help more with multi-talker babble or continuous noise, so this result may not apply to all noisy environments. The findings were calculated as percentages of correct words, which makes direct comparison to decibel-based studies difficult.
Declared interests
One co-author is an employee of Advanced Bionics, the manufacturer of the processors used in the study. The research was funded by the National Institutes of Health.
The easy way to misread this
Do not assume that larger summation or squelch benefits in asymmetrical listeners prove better binaural hearing. The authors explain these gains were likely just the result of adding a better-functioning ear to a poor one, not improved central processing.