Discriminability and Perceptual Saliency of Temporal and Spectral Cues for Final Fricative Consonant Voicing in Simulated Cochlear-Implant and Bimodal Hearing.
Multiple redundant acoustic cues can contribute to the perception of a single phonemic contrast. This study investigated the effect of spectral degradation on the discriminability and perceptual saliency of acoustic cues for identification of word-final fricative voicing in "loss" versus "laws", and possible changes that occurred when low-frequency acoustic cues were restored. Three acoustic cues that contribute to the word-final /s/-/z/ contrast (first formant frequency [F1] offset, vowel-consonant duration ratio, and consonant voicing duration) were systematically varied in synthesized words. A discrimination task measured listeners' ability to discriminate differences among stimuli within a single cue dimension. A categorization task examined the extent to which listeners make use of a given cue to label a syllable as "loss" versus "laws" when multiple cues are available. Normal-hearing listeners were presented with stimuli that were either unprocessed, processed with an eight-channel noise-band vocoder to approximate spectral degradation in cochlear implants, or low-pass filtered. Listeners were tested in four listening conditions: unprocessed, vocoder, low-pass, and a combined vocoder + low-pass condition that simulated bimodal hearing. Results showed a negative impact of spectral degradation on F1 cue discrimination and a trading relation between spectral and temporal cues in which listeners relied more heavily on the temporal cues for "loss-laws" identification when spectral cues were degraded. Furthermore, the addition of low-frequency fine-structure cues in simulated bimodal hearing increased the perceptual saliency of the F1 cue for "loss-laws" identification compared with vocoded speech. Findings suggest an interplay between the quality of sensory input and cue importance.
Department of Communication Sciences and Disorders, Northeastern University, Boston, MA, USA yykong@neu.edu.
Ying-Yee
YY
Kong
Department of Speech and Hearing Sciences, University of Washington, Seattle, WA, USA.
Matthew B
MB
Winn
Department of Communication Sciences and Disorders, Northeastern University, Boston, MA, USA.
Katja
K
Poellmann
Department of Communication Sciences & Disorders, University of South Florida, Tampa, FL, USA.
Gail S
GS
Donaldson
D000161:Acoustic Stimulation; D019929:Cochlear Implantation; D003054:Cochlear Implants; D003463:Cues; D006801:Humans; D010700:Phonetics; D013067:Speech Perception
bimodal hearing; cochlear implant; cue weighting; spectral degradation