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Description
Two groups of cochlear implant (CI) listeners were tested for sound source localization and for speech recognition in complex listening environments. One group (n=11) wore bilateral CIs and, potentially, had access to interaural level difference (ILD) cues, but not interaural timing difference (ITD) cues. The second group (n=12) wore a

Two groups of cochlear implant (CI) listeners were tested for sound source localization and for speech recognition in complex listening environments. One group (n=11) wore bilateral CIs and, potentially, had access to interaural level difference (ILD) cues, but not interaural timing difference (ITD) cues. The second group (n=12) wore a single CI and had low-frequency, acoustic hearing in both the ear contralateral to the CI and in the implanted ear. These `hearing preservation' listeners, potentially, had access to ITD cues but not to ILD cues. At issue in this dissertation was the value of the two types of information about sound sources, ITDs and ILDs, for localization and for speech perception when speech and noise sources were separated in space. For Experiment 1, normal hearing (NH) listeners and the two groups of CI listeners were tested for sound source localization using a 13 loudspeaker array. For the NH listeners, the mean RMS error for localization was 7 degrees, for the bilateral CI listeners, 20 degrees, and for the hearing preservation listeners, 23 degrees. The scores for the two CI groups did not differ significantly. Thus, both CI groups showed equivalent, but poorer than normal, localization. This outcome using the filtered noise bands for the normal hearing listeners, suggests ILD and ITD cues can support equivalent levels of localization. For Experiment 2, the two groups of CI listeners were tested for speech recognition in noise when the noise sources and targets were spatially separated in a simulated `restaurant' environment and in two versions of a `cocktail party' environment. At issue was whether either CI group would show benefits from binaural hearing, i.e., better performance when the noise and targets were separated in space. Neither of the CI groups showed spatial release from masking. However, both groups showed a significant binaural advantage (a combination of squelch and summation), which also maintained separation of the target and noise, indicating the presence of some binaural processing or `unmasking' of speech in noise. Finally, localization ability in Experiment 1 was not correlated with binaural advantage in Experiment 2.
ContributorsLoiselle, Louise (Author) / Dorman, Michael F. (Thesis advisor) / Yost, William A. (Thesis advisor) / Azuma, Tamiko (Committee member) / Liss, Julie (Committee member) / Arizona State University (Publisher)
Created2013
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Description
A multitude of individuals across the globe suffer from hearing loss and that number continues to grow. Cochlear implants, while having limitations, provide electrical input for users enabling them to "hear" and more fully interact socially with their environment. There has been a clinical shift to the

A multitude of individuals across the globe suffer from hearing loss and that number continues to grow. Cochlear implants, while having limitations, provide electrical input for users enabling them to "hear" and more fully interact socially with their environment. There has been a clinical shift to the bilateral placement of implants in both ears and to bimodal placement of a hearing aid in the contralateral ear if residual hearing is present. However, there is potentially more to subsequent speech perception for bilateral and bimodal cochlear implant users than the electric and acoustic input being received via these modalities. For normal listeners vision plays a role and Rosenblum (2005) points out it is a key feature of an integrated perceptual process. Logically, cochlear implant users should also benefit from integrated visual input. The question is how exactly does vision provide benefit to bilateral and bimodal users. Eight (8) bilateral and 5 bimodal participants received randomized experimental phrases previously generated by Liss et al. (1998) in auditory and audiovisual conditions. The participants recorded their perception of the input. Data were consequently analyzed for percent words correct, consonant errors, and lexical boundary error types. Overall, vision was found to improve speech perception for bilateral and bimodal cochlear implant participants. Each group experienced a significant increase in percent words correct when visual input was added. With vision bilateral participants reduced consonant place errors and demonstrated increased use of syllabic stress cues used in lexical segmentation. Therefore, results suggest vision might provide perceptual benefits for bilateral cochlear implant users by granting access to place information and by augmenting cues for syllabic stress in the absence of acoustic input. On the other hand vision did not provide the bimodal participants significantly increased access to place and stress cues. Therefore the exact mechanism by which bimodal implant users improved speech perception with the addition of vision is unknown. These results point to the complexities of audiovisual integration during speech perception and the need for continued research regarding the benefit vision provides to bilateral and bimodal cochlear implant users.
ContributorsLudwig, Cimarron (Author) / Liss, Julie (Thesis advisor) / Dorman, Michael (Committee member) / Azuma, Tamiko (Committee member) / Arizona State University (Publisher)
Created2015
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Description
In the noise and commotion of daily life, people achieve effective communication partly because spoken messages are replete with redundant information. Listeners exploit available contextual, linguistic, phonemic, and prosodic cues to decipher degraded speech. When other cues are absent or ambiguous, phonemic and prosodic cues are particularly important

In the noise and commotion of daily life, people achieve effective communication partly because spoken messages are replete with redundant information. Listeners exploit available contextual, linguistic, phonemic, and prosodic cues to decipher degraded speech. When other cues are absent or ambiguous, phonemic and prosodic cues are particularly important because they help identify word boundaries, a process known as lexical segmentation. Individuals vary in the degree to which they rely on phonemic or prosodic cues for lexical segmentation in degraded conditions.

Deafened individuals who use a cochlear implant have diminished access to fine frequency information in the speech signal, and show resulting difficulty perceiving phonemic and prosodic cues. Auditory training on phonemic elements improves word recognition for some listeners. Little is known, however, about the potential benefits of prosodic training, or the degree to which individual differences in cue use affect outcomes.

The present study used simulated cochlear implant stimulation to examine the effects of phonemic and prosodic training on lexical segmentation. Participants completed targeted training with either phonemic or prosodic cues, and received passive exposure to the non-targeted cue. Results show that acuity to the targeted cue improved after training. In addition, both targeted attention and passive exposure to prosodic features led to increased use of these cues for lexical segmentation. Individual differences in degree and source of benefit point to the importance of personalizing clinical intervention to increase flexible use of a range of perceptual strategies for understanding speech.
ContributorsHelms Tillery, Augusta Katherine (Author) / Liss, Julie M. (Thesis advisor) / Azuma, Tamiko (Committee member) / Brown, Christopher A. (Committee member) / Dorman, Michael F. (Committee member) / Utianski, Rene L. (Committee member) / Arizona State University (Publisher)
Created2015
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Description
An increasing number of military veterans are enrolling in college, primarily due to the Post-9/11 GI Bill, which provides educational benefits to veterans who served on active duty since September 11, 2001. With rigorous training, active combat situations, and exposure to unexpected situations, the veteran population is at a higher

An increasing number of military veterans are enrolling in college, primarily due to the Post-9/11 GI Bill, which provides educational benefits to veterans who served on active duty since September 11, 2001. With rigorous training, active combat situations, and exposure to unexpected situations, the veteran population is at a higher risk for traumatic brain injury (TBI), Post Traumatic Stress Disorder (PTSD), and depression. All of these conditions are associated with cognitive consequences, including attention deficits, working memory problems, and episodic memory impairments. Some conditions, particularly mild TBI, are not diagnosed or treated until long after the injury when the person realizes they have cognitive difficulties. Even mild cognitive problems can hinder learning in an academic setting, but there is little data on the frequency and severity of cognitive deficits in veteran college students. The current study examines self-reported cognitive symptoms in veteran students compared to civilian students and how those symptoms relate to service-related conditions. A better understanding of the pattern of self-reported symptoms will help researchers and clinicians determine the veterans who are at higher risk for cognitive and academic difficulties.
ContributorsAllen, Kelly Anne (Author) / Azuma, Tamiko (Thesis director) / Gallagher, Karen (Committee member) / Department of Speech and Hearing Science (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
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Description
The increase of Traumatic Brain Injury (TBI) cases in recent war history has increased the urgency of research regarding how veterans are affected by TBIs. The purpose of this study was to evaluate the effects of TBI on speech recognition in noise. The AzBio Sentence Test was completed for signal-to-noise

The increase of Traumatic Brain Injury (TBI) cases in recent war history has increased the urgency of research regarding how veterans are affected by TBIs. The purpose of this study was to evaluate the effects of TBI on speech recognition in noise. The AzBio Sentence Test was completed for signal-to-noise ratios (S/N) from -10 dB to +15 dB for a control group of ten participants and one US military veteran with history of service-connected TBI. All participants had normal hearing sensitivity defined as thresholds of 20 dB or better at frequencies from 250-8000 Hz in addition to having tympanograms within normal limits. Comparison of the data collected on the control group versus the veteran suggested that the veteran performed worse than the majority of the control group on the AzBio Sentence Test. Further research with more participants would be beneficial to our understanding of how veterans with TBI perform on speech recognition tests in the presence of background noise.
ContributorsCorvasce, Erica Marie (Author) / Peterson, Kathleen (Thesis director) / Williams, Erica (Committee member) / Azuma, Tamiko (Committee member) / Barrett, The Honors College (Contributor) / Department of Speech and Hearing Science (Contributor)
Created2015-05
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Description
Working memory and cognitive functions contribute to speech recognition in normal hearing and hearing impaired listeners. In this study, auditory and cognitive functions are measured in young adult normal hearing, elderly normal hearing, and elderly cochlear implant subjects. The effects of age and hearing on the different measures are investigated.

Working memory and cognitive functions contribute to speech recognition in normal hearing and hearing impaired listeners. In this study, auditory and cognitive functions are measured in young adult normal hearing, elderly normal hearing, and elderly cochlear implant subjects. The effects of age and hearing on the different measures are investigated. The correlations between auditory/cognitive functions and speech/music recognition are examined. The results may demonstrate which factors can better explain the variable performance across elderly cochlear implant users.
ContributorsKolberg, Courtney Elizabeth (Author) / Luo, Xin (Thesis director) / Azuma, Tamiko (Committee member) / Department of Speech and Hearing Science (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
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Description
When listeners hear sentences presented simultaneously, the listeners are better able to discriminate between speakers when there is a difference in fundamental frequency (F0). This paper explores the use of a pulse train vocoder to simulate cochlear implant listening. A pulse train vocoder, rather than a noise or tonal vocoder,

When listeners hear sentences presented simultaneously, the listeners are better able to discriminate between speakers when there is a difference in fundamental frequency (F0). This paper explores the use of a pulse train vocoder to simulate cochlear implant listening. A pulse train vocoder, rather than a noise or tonal vocoder, was used so the fundamental frequency (F0) of speech would be well represented. The results of this experiment showed that listeners are able to use the F0 information to aid in speaker segregation. As expected, recognition performance is the poorest when there was no difference in F0 between speakers, and listeners performed better as the difference in F0 increased. The type of errors that the listeners made was also analyzed. The results show that when an error was made in identifying the correct word from the target sentence, the response was usually (~60%) a word that was uttered in the competing sentence.
ContributorsStanley, Nicole Ernestine (Author) / Yost, William (Thesis director) / Dorman, Michael (Committee member) / Liss, Julie (Committee member) / Barrett, The Honors College (Contributor) / Department of Speech and Hearing Science (Contributor) / Hugh Downs School of Human Communication (Contributor)
Created2013-05
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Description
Mild TBI (mTBI) has been associated with subtle executive function (EF) and

cognitive-communication deficits. In bilinguals, there are unique cognitive demands required to control and process two languages effectively. Surprisingly, little is known about the impact of mTBI on EF, communication, and language control in bilinguals. Therefore, the aim of this

Mild TBI (mTBI) has been associated with subtle executive function (EF) and

cognitive-communication deficits. In bilinguals, there are unique cognitive demands required to control and process two languages effectively. Surprisingly, little is known about the impact of mTBI on EF, communication, and language control in bilinguals. Therefore, the aim of this study was to examine the cognitive-communication abilities in bilinguals with a history of mTBI, identify any language control impairments, and explore the relationship between these language control impairments and domain-general cognitive control abilities. To this end, three-hundred and twenty-seven monolingual and bilingual college students with and without mTBI history participated in two experiments. In these experiments, EF, communication, and language control were examined using experimental and clinical tasks as well as self-rating scales. In Experiment 1, there was an interaction between mTBI history and language group (monolinguals vs. bilinguals) in how participants performed on a clinical measure of EF and a verbal fluency task. That is, only bilinguals with mTBI scored significantly lower on these tasks. In addition, there was a significant correlation between errors on a language switching task and performance on non-verbal EF tasks. In Experiment 2, a subgroup of bilinguals with persistent cognitive and behavioral symptoms reported greater everyday communication challenges in their first and second languages. Also, unbalanced bilinguals reported greater EF difficulties than monolinguals and balanced bilinguals regardless of mTBI history. In conclusion, bilinguals may face unique cognitive-communication challenges after mTBI. Factors related to the bilingual experience (e.g., language balance, daily language use) should be

considered in clinical evaluation and future research.
ContributorsAlateeq, Halah (Author) / Azuma, Tamiko (Thesis advisor) / Ratiu, Ileana (Committee member) / Lavoie, Michael (Committee member) / Arizona State University (Publisher)
Created2020