Cochlear-implant simulation mimics increased age in temporal processing of syllables by young and middle-aged normal-hearing listeners

Abstract

To better understand the effects of signal quality on phonetic processing, the present study examines the effects of signal degradation on processing of two-syllable sequences by young and middle-aged normal-hearing listeners. Temporal processing of American-English vowel sequences was compared across unprocessed and cochlear-implant (CI) simulation conditions for young listeners and for a CI simulation condition for the middle-aged listeners. Using the method of Fogerty, Humes and Kewley-Port [J. Acoust. Soc. Am. 127, 2509–2520 (2010)], listeners heard 70-ms, resynthesized versions of four syllables (“pit, pet, put, pot”) in a two-syllable temporal-order processing task. Task difficulty was adjusted by increasing or decreasing syllable-onset asynchrony (SOA), i.e., the duration between syllable onsets. SOA thresholds for accuracy of syllable-sequence identification was estimated using the method of constant stimuli on each of four 72-trial blocks. Results for the CI simulation conditions for both listener groups were comparable to those for the next older age-group in Fogerty et al. (2010), i.e., young adult listeners performed similarly to the middle-aged listeners Fogerty et al., and middle-aged listeners performed similarly to the older listeners Fogerty et al. Results will be discussed with regard to implications for phonetic processing of speech in demanding listening conditions and practical implications for CI users.