Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
Browse
2 results
Search Results
Item The use of acoustic cues in phonetic perception: Effects of spectral degradation, limited bandwidth and background noise(2011) Winn, Matthew Brandon; Chatterjee, Monita; Idsardi, William J; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Hearing impairment, cochlear implantation, background noise and other auditory degradations result in the loss or distortion of sound information thought to be critical to speech perception. In many cases, listeners can still identify speech sounds despite degradations, but understanding of how this is accomplished is incomplete. Experiments presented here tested the hypothesis that listeners would utilize acoustic-phonetic cues differently if one or more cues were degraded by hearing impairment or simulated hearing impairment. Results supported this hypothesis for various listening conditions that are directly relevant for clinical populations. Analysis included mixed-effects logistic modeling of contributions of individual acoustic cues for various contrasts. Listeners with cochlear implants (CIs) or normal-hearing (NH) listeners in CI simulations showed increased use of acoustic cues in the temporal domain and decreased use of cues in the spectral domain for the tense/lax vowel contrast and the word-final fricative voicing contrast. For the word-initial stop voicing contrast, NH listeners made less use of voice-onset time and greater use of voice pitch in conditions that simulated high-frequency hearing impairment and/or masking noise; influence of these cues was further modulated by consonant place of articulation. A pair of experiments measured phonetic context effects for the "s/sh" contrast, replicating previously observed effects for NH listeners and generalizing them to CI listeners as well, despite known deficiencies in spectral resolution for CI listeners. For NH listeners in CI simulations, these context effects were absent or negligible. Audio-visual delivery of this experiment revealed enhanced influence of visual lip-rounding cues for CI listeners and NH listeners in CI simulations. Additionally, CI listeners demonstrated that visual cues to gender influence phonetic perception in a manner consistent with gender-related voice acoustics. All of these results suggest that listeners are able to accommodate challenging listening situations by capitalizing on the natural (multimodal) covariance in speech signals. Additionally, these results imply that there are potential differences in speech perception by NH listeners and listeners with hearing impairment that would be overlooked by traditional word recognition or consonant confusion matrix analysis.Item Social and Emotional Functioning of Children with Cochlear Implants(2005-04-18) Schorr, Efrat; Fox, Nathan A; Human Development; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Studies of infants and children have demonstrated the importance of sensory processing in facilitating social and emotional development. Children who are deaf are deprived of the information typically provided by the auditory modality that is necessary to the development of basic social and emotional skills, which serve as the foundation upon which complex social and emotional constructs are built. Children with cochlear implants experience extended periods of total auditory deprivation during early childhood, followed by the introduction of auditory stimulation. Thirty-nine children with cochlear implants, aged five through fourteen, as well as an age and sex matched group of normal hearing peers, participated in assessment of the integrated perception of multimodal stimuli, processing of facial and vocal expressions of emotion, and emotion understanding skills. These dimensions of basic social and emotional functioning are vulnerable to the effects of atypical early experience. The age at which children received their cochlear implant and the length of time that they have used the cochlear implant were hypothesized to predict performance on the assessments. Results showed that the age at implant predicted performance on the McGurk fusion task, which requires the integration of multimodal sensory stimuli. Specifically, children who received their cochlear implant prior to age 30 months accurately identified the incongruent auditory-visual stimuli, whereas children who received their cochlear implant after 30 months of age did not. Age at implant and duration of implant use did not predict performance on the other experimental tasks. Comparison of groups revealed that performance of children with cochlear implants did not differ from children with normal hearing in a facial emotion identification task and in 2 components of emotion understanding: receptive identification of facial expressions and affective-perspective taking. Children with cochlear implants demonstrated poorer performance than children with normal hearing in tasks requiring free labeling of facial expressions of emotion, and vocal emotion identification. This research suggests sensitive periods in multimodal sensory integration. The present study provides understanding of the social and emotional influences of early experience with the auditory system on children with cochlear implants.