Effect of Noise Reduction Gain Errors on Simulated Cochlear Implant Speech Intelligibility.
Abigail A Kressner, Tobias May, Torsten Dau
PMID 30755108WHAT IT FOUND
Correcting noise-reduction errors in speech gaps helped only when transitions were also accurate.
In simulated cochlear implant listening, gap-only fixes had little benefit in stationary noise, and transition-only fixes were weak.
Key findings
01Correcting gain errors in the speech gaps significantly improved speech reception thresholds only in modulated noise, not in stationary noise.
02Correcting gain errors in the transition regions alone did not significantly improve speech reception thresholds in either noise type.
03When only one temporal region had errors, gap-region errors were more detrimental than speech-region or transition-region errors.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study used normal-hearing listeners with a cochlear implant simulation, not cochlear implant recipients, so the results may not match what CI users experience. The speech, gap, and transition regions were segmented by a heuristic method, and transitions were fixed at 20 ms, which may have mislabeled true transitions. The sentences used a male talker whose speech was dominated by low-frequency information, so effects may differ with other talkers or corpora. The listeners did not show dip listening in modulated noise, possibly because the vocoder had overlapping carrier bands, which may limit how well the simulation represents normal-hearing listening. The first six participants had an extended protocol with repeated sentences, and repeated scores were discarded, leaving a relatively small sample of 30 listeners.
Declared interests
The study was funded by the Danish Council for Independent Research. The supplied text does not report author conflicts of interest.
The easy way to misread this
Do not conclude that suppressing noise in speech gaps will improve speech understanding for cochlear implant recipients. The study used normal-hearing listeners with a simulation, not cochlear implant recipients, and gap-only correction helped only in modulated noise and depended on accurate transition encoding.