Effects of insertion depth on spatial speech perception in noise for simulations of cochlear implants and single-sided deafness.
Xiaoqing Zhou, Huajun Li, John J Galvin and 2 others
PMID 27367147WHAT IT FOUND
In simulated single-sided deafness, adding a cochlear implant side helped mainly when speech and noise came from different places.
Deeper insertion improved that benefit, but it stayed far below normal hearing.
Key findings
01With simulated cochlear implant input, the main binaural benefit came from head shadow; summation and squelch benefits were small.
02Deeper simulated insertion improved head shadow benefit: 3.6 dB for the 19 mm insertion, 4.7 dB for the 22 mm insertion and 8.4 dB for the 25 mm insertion.
03Even the deepest simulation gave less head shadow benefit than original speech, 8.4 dB versus 19.9 dB.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
This was a laboratory simulation in normal-hearing listeners, not a test in people who actually have single-sided deafness or cochlear implants. Only ten participants were tested, all young adults who spoke Mandarin as a native language. The study used one sentence list per condition, so differences between lists could have affected the thresholds. The CI simulation used a 16-channel vocoder and fixed insertion depths, which may not match any real implant or patient. The study measured acute thresholds in noise, so it cannot show long-term adaptation, real-world communication, or quality-of-life effects.
The easy way to misread this
Do not conclude that a deeper cochlear implant insertion will give patients normal speech-in-noise understanding. This was a simulation in ten normal-hearing Mandarin speakers, not real cochlear implant users, and the deepest insertion still gave only 8.4 dB head shadow benefit compared with 19.9 dB for original speech.