Title
The Perception of Contrastive Stress in Vocoded Speech: Implications for Cochlear Implant Users
Abstract
Vocoded speech is used frequently to simulate cochlear implant processing in normalhearing
listeners (Loebach, 2007; Oxenham & Kreft, 2014). Speech signals are band-pass
filtered at the first stage of processing and outputs of each of these filters are subsequently lowpass
filtered. Varying the values of low-pass filter cutoffs influences periodicity cues conveyed
through vocoded speech, with higher values passing more periodicity cues and lower levels
reducing these cues. We examined the effect that limiting periodicity cues have in the perception
of contrastive stress. Previous research showed that both spectral and temporal features of
sentence stimuli are varied when speakers use contrastive stress (Cooper, Eady, & Mueller,
1985). We were primarily interested in how variations in spectral, temporal, and intensity
features of vocoded speech influenced the perception of contrastive stress. We presented stimuli
to participants in four conditions of a contrastive stress experimental test: unprocessed, natural
speech and three processed speech conditions with low-pass filter cutoffs at 50 Hz, 160 Hz, and
250 Hz. Participants were assigned to only one filter condition. We also evaluated how talker
and syntactic place influenced the perception of contrastive stress. There were four talkers and
four syntactic stress conditions. All participants received were sentence stimuli for each talker
and syntactic stress condition. We found significant perception effects for filter condition, talker,
and place, as well as a significant interaction of talker by place. These outcomes suggest that the
perception of contrastive stress in vocoded speech is influenced by a number of factors,
including: (1) the availability of periodicity cues primarily conveyed by fundamental frequency,
(2) talker variation, and (3) syntactic place of the stressed word in a sentence. The results may
partially explain the range of performance experienced by cochlear implant users in tasks that
test the perception of suprasegmental cues.
Suggested Citation
Klang, Alix.
(2017).
The Perception of Contrastive Stress in Vocoded Speech: Implications for Cochlear Implant Users.
Retrieved from the University of Minnesota Digital Conservancy,
https://hdl.handle.net/11299/189092.