Counting or discriminating the number of voices to assess binaural fusion with single-sided vocoders

For single-sided deafness cochlear-implant (SSD-CI) listeners, different peripheral representations for electric versus acoustic stimulation, combined with interaural frequency mismatch, might limit the ability to perceive bilaterally presented speech as a single voice. The assessment of binaural fu...

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Bibliographic Details
Published in:The Journal of the Acoustical Society of America 2020-01, Vol.147 (1), p.446-458
Main Authors: Wess, Jessica M, Spencer, Nathaniel J, Bernstein, Joshua G W
Format: Article
Language:English
Subjects:
Acoustic Stimulation
Adolescent
Adult
Cochlear Implants
Discrimination, Psychological
Humans
Psychoacoustics
Signal Processing, Computer-Assisted
Speech Discrimination Tests
Speech Perception
Young Adult
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Summary:For single-sided deafness cochlear-implant (SSD-CI) listeners, different peripheral representations for electric versus acoustic stimulation, combined with interaural frequency mismatch, might limit the ability to perceive bilaterally presented speech as a single voice. The assessment of binaural fusion often relies on subjective report, which requires listeners to have some understanding of the perceptual phenomenon of object formation. Two experiments explored whether binaural fusion could instead be assessed using judgments of the number of voices in a mixture. In an SSD-CI simulation, normal-hearing listeners were presented with one or two "diotic" voices (i.e., unprocessed in one ear and noise-vocoded in the other) in a mixture with additional monaural voices. In experiment 1, listeners reported how many voices they heard. Listeners generally counted the diotic speech as two separate voices, regardless of interaural frequency mismatch. In experiment 2, listeners identified which of two mixtures contained diotic speech. Listeners performed significantly better with interaurally frequency-matched than with frequency-mismatched stimuli. These contrasting results suggest that listeners experienced partial fusion: not enough to count the diotic speech as one voice, but enough to detect its presence. The diotic-speech detection task (experiment 2) might provide a tool to evaluate fusion and optimize frequency mapping for SSD-CI patients.
ISSN:0001-4966
1520-8524
1520-8524
DOI:10.1121/10.0000511