Matching Items (4)
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- All Subjects: Cochlear Implants
- All Subjects: Particle Image Velocimetry
- Creators: Frakes, David
- Member of: Barrett, The Honors College Thesis/Creative Project Collection
- Resource Type: Text
Description
The ability of cochlear implants (CI) to restore auditory function has advanced significantly in the past decade. Approximately 96,000 people in the United States benefit from these devices, which by the generation and transmission of electrical impulses, enable the brain to perceive sound. But due to the predominantly Western cochlear implant market, current CI characterization primarily focuses on improving the quality of American English. Only recently has research begun to evaluate CI performance using other languages such as Mandarin Chinese, which rely on distinct spectral characteristics not present in English. Mandarin, a tonal language utilizes four, distinct pitch patterns, which when voiced a syllable, conveys different meanings for the same word. This presents a challenge to hearing research as spectral, or frequency based information like pitch is readily acknowledged to be significantly reduced by CI processing algorithms. Thus the present study sought to identify the intelligibility differences for English and Mandarin when processed using current CI strategies. The objective of the study was to pinpoint any notable discrepancies in speech recognition, using voice-coded (vocoded) audio that simulates a CI generated stimuli. This approach allowed 12 normal hearing English speakers, and 9 normal hearing Mandarin listeners to participate in the experiment. The number of frequency channels available and the carrier type of excitation were varied in order to compare their effects on two cases of Mandarin intelligibility: Case 1) word recognition and Case 2) combined word and tone recognition. The results indicated a statistically significant difference between English and Mandarin intelligibility for Condition 1 (8Ch-Sinewave Carrier, p=0.022) given Case 1 and Condition 1 (8Ch-Sinewave Carrier, p=0.001) and Condition 3 (16Ch-Sinewave Carrier, p=0.001) given Case 2. The data suggests that the nature of the carrier type does have an effect on tonal language intelligibility and warrants further research as a design consideration for future cochlear implants.
ContributorsSchiltz, Jessica Hammitt (Author) / Berisha, Visar (Thesis director) / Frakes, David (Committee member) / Barrett, The Honors College (Contributor) / Harrington Bioengineering Program (Contributor)
Created2015-05
Description
Intracranial aneurysms, which form in the blood vessels of the brain, are particularly dangerous because of the importance and fragility of the human brain. When an intracranial aneurysm gets large it poses a significant risk of bursting and causing subarachnoid hemorrhaging (SAH), a possibly fatal condition. One possible treatment involves placing a stent in the vessel to act as a flow diverter. In this study we look at the hemodynamics of two geometries of idealized basilar tip aneurysms, at 2,3, and 4 ml/s pulsatile flow, at three different points in the cardiac cycle. The smaller model had neck and dome diameters of 2.67 mm and 4 mm respectively, while the larger aneurysm had neck and dome diameters of 3 mm and 6 mm respectively. Both diameters and the dome to neck ratio increased in the second model, representing growth over time. Flow was analyzed using stereoscopic particle image velocimetry (PIV) for both geometries in untreated models, as well as after treatment with a high porosity Enterprise stent (Codman and Shurtleff Inc.). Flow in the models was characterized by root mean square velocity in the aneurysm and neck plane, cross neck flow, max aneurysm vorticity, and total aneurysm kinetic energy. It was found that in the smaller aneurysm model (model 1), Enterprise stent treatment reduced all flow parameters substantially. The smallest reduction was in max vorticity, at 42.48%, and the largest in total kinetic energy, at 75.69%. In the larger model (model 2) there was a 52.18% reduction in cross neck flow, but a 167.28% increase in aneurysm vorticity. The other three parameters experienced little change. These results, along with observed velocity vector fields, indicate a noticeable diversion of flow away from the aneurysm in the stent treated model 1. Treatment in model 2 had a small flow diversion effect, but also altered flow in unpredictable ways, in some cases having a detrimental effect on aneurysm hemodynamics. The results of this study indicate that Enterprise stent treatment is only effective in small, relatively undeveloped aneurysm geometries, and waiting until an aneurysm has grown too large can eliminate this treatment option altogether.
ContributorsLindsay, James Bryan (Author) / Frakes, David (Thesis director) / LaBelle, Jeffrey (Committee member) / Nair, Priya (Committee member) / Barrett, The Honors College (Contributor) / School of Humanities, Arts, and Cultural Studies (Contributor)
Created2013-05
Description
This study investigates the application of Computational Fluid Dynamics (CFD) to the medical field. An overview of recent advances in computational simulation and modeling in medical applications is provided, with a particular emphasis on CFD. This study attempts to validate CFD and demonstrate the possibility for applying CFD to the clinical treatment and evaluation of atherosclerotic disease. Three different geometric configurations are investigated: one idealized bifurcation with a primary diameter of 8 mm, and two different patient-specific models of the bifurcation from the common femoral artery to the superficial and deep femoral arteries. CFD is compared against experimental measurements of steady state and pulsatile flow acquired with Particle Image Velocimetry (PIV). Steady state and pulsatile flow rates that are consistent with those observed in the femoral artery are used. In addition, pulsatile CFD simulations are analyzed in order to demonstrate meaningful clinical applications for studying and evaluating the treatment of atherosclerotic disease. CFD was successfully validated for steady state flow, with an average percent error of 6.991%. Potential for validation was also demonstrated for pulsatile flow, but methodological errors warrant further investigation to reformulate methods and analyze results. Quantities frequently associated with atherosclerotic disease and arterial bifurcations, such as large variations in wall shear stress and the presence of recirculation zones are demonstrated from the pulsatile CFD simulations. Further study is required in order to evaluate whether or not such phenomena are represented by CFD accurately. Further study must also be performed in order to evaluate the practicality and utility of CFD for the evaluation of atherosclerotic disease treatment.
ContributorsMortensen, Matthew James (Author) / VanAuker, Michael (Thesis director) / Frakes, David (Committee member) / Harrington Bioengineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Cochlear implant (CI) successfully restores hearing sensation to profoundly deaf patients, but its
performance is limited by poor spectral resolution. Acoustic CI simulation has been widely used
in normal-hearing (NH) listeners to study the effect of spectral resolution on speech perception,
while avoiding patient-related confounds. It is unclear how speech production may change with
the degree of spectral degradation of auditory feedback as experience by CI users. In this study,
a real-time sinewave CI simulation was developed to provide NH subjects with auditory
feedback of different spectral resolution (1, 2, 4, and 8 channels). NH subjects were asked to
produce and identify vowels, as well as recognize sentences while listening to the real-time CI
simulation. The results showed that sentence recognition scores with the real-time CI simulation
improved with more channels, similar to those with the traditional off-line CI simulation.
Perception of a vowel continuum “HEAD”- “HAD” was near chance with 1, 2, and 4 channels,
and greatly improved with 8 channels and full spectrum. The spectral resolution of auditory
feedback did not significantly affect any acoustic feature of vowel production (e.g., vowel space
area, mean amplitude, mean and variability of fundamental and formant frequencies). There
was no correlation between vowel production and perception. The lack of effect of auditory
feedback spectral resolution on vowel production was likely due to the limited exposure of NH
subjects to CI simulation and the limited frequency ranges covered by the sinewave carriers of
CI simulation. Future studies should investigate the effects of various CI processing parameters
on speech production using a noise-band CI simulation.
performance is limited by poor spectral resolution. Acoustic CI simulation has been widely used
in normal-hearing (NH) listeners to study the effect of spectral resolution on speech perception,
while avoiding patient-related confounds. It is unclear how speech production may change with
the degree of spectral degradation of auditory feedback as experience by CI users. In this study,
a real-time sinewave CI simulation was developed to provide NH subjects with auditory
feedback of different spectral resolution (1, 2, 4, and 8 channels). NH subjects were asked to
produce and identify vowels, as well as recognize sentences while listening to the real-time CI
simulation. The results showed that sentence recognition scores with the real-time CI simulation
improved with more channels, similar to those with the traditional off-line CI simulation.
Perception of a vowel continuum “HEAD”- “HAD” was near chance with 1, 2, and 4 channels,
and greatly improved with 8 channels and full spectrum. The spectral resolution of auditory
feedback did not significantly affect any acoustic feature of vowel production (e.g., vowel space
area, mean amplitude, mean and variability of fundamental and formant frequencies). There
was no correlation between vowel production and perception. The lack of effect of auditory
feedback spectral resolution on vowel production was likely due to the limited exposure of NH
subjects to CI simulation and the limited frequency ranges covered by the sinewave carriers of
CI simulation. Future studies should investigate the effects of various CI processing parameters
on speech production using a noise-band CI simulation.
ContributorsPerez Lustre, Sarahi (Author) / Luo, Xin (Thesis director) / Daliri, Ayoub (Committee member) / Division of Teacher Preparation (Contributor) / College of Health Solutions (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2019-05