Abstract
A vocoder is used to simulate cochlear-implant sound processing in normal-hearing listeners. Typically, there is rapid improvement in vocoded speech recognition, but it is unclear if the improvement rate differs across age groups and speech materials. Children (8–10 years) and young adults (18–26 years) were trained and tested over 2 days (4 hours) on recognition of eight-channel noise-vocoded words and sentences, in quiet and in the presence of multi-talker babble at signal-to-noise ratios of 0, +5, and +10 dB. Children achieved poorer performance than adults in all conditions, for both word and sentence recognition. With training, vocoded speech recognition improvement rates were not significantly different between children and adults, suggesting that improvement in learning how to process speech cues degraded via vocoding is absent of developmental differences across these age groups and types of speech materials. Furthermore, this result confirms that the acutely measured age difference in vocoded speech recognition persists after extended training.
Highlights
Cochlear-implant (CI) users show substantial variability in speech recognition performance [1,2], a result of biological, surgical, and device-related factors [3]
An acoustic signal is bandpass filtered into a limited number of channels, the temporal envelope is extracted from each channel, and these slowly varying envelopes are used to modulate a carrier signal such as a narrowband noise [5]
The type of acoustic carrier affects performance because it affects the representation of the temporal envelope and the spectrum [9,10]
Summary
Cochlear-implant (CI) users show substantial variability in speech recognition performance [1,2], a result of biological, surgical, and device-related factors [3]. To remove some of the unknown sources of variability in speech recognition performance, CI users’ performance can be studied using acoustic simulations of CI processing, a multi-channel vocoder, presented to normal-hearing (NH) listeners [4]. The way that the signal processing and CI simulation is performed, as well as other methodological choices, affect vocoded speech recognition performance. A larger number of vocoder channels increases performance because of improved spectral-temporal representation of the original acoustics [6,7,8]. The type of acoustic carrier affects performance because it affects the representation of the temporal envelope and the spectrum [9,10].
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