Thesis (Ph. D.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Mechanical Engineering, 2009. / Includes bibliographical references.

Mode of access: Internet via World Wide Web. Available at http://hdl.handle.net/1947/9701. / "October 2008" Title from PDF cover (viewed on 25 September, 2009) Includes bibliographical references.

Thesis (Ph. D.)--University of Oregon, 2000. / Title from title screen. Extent of document: xiv, 152 p. : ill. Includes vita and abstract. Includes bibliographical references (p. 146-152).

Thesis (Ph.D.) - University of Queensland, 2006. / Includes bibliography.

Thesis (M.S.)--Rochester Institute of Technology, 2007. / Typescript. Includes bibliographical references (leaves 161-164).

Advisers: Terry Takahashi and Richard Marrocco. xiv, 152 p. / Neurons in the barn owl's inferior colliculus (IC) derive their spatial receptive fields (RF) from two auditory cues: interaural time difference (ITD) and interaural level difference (ILD). ITD serves to restrict a RF in azimuth but the precise role of ILD was, up to this point, unclear. Filtering by the ears and head insures that each spatial location is associated with a unique combination of frequency-specific ILD values (i.e., an ILD spectrum). We isolated the effect of ILD spectra using virtual sound sources in which ITD was held fixed for all spatial locations while ILD spectra were allowed to vary normally. A cell's response to these stimuli reflects the contribution of ILD to spatial tuning, referred to as an “ILD-alone RF”. In a sample of 34 cells, individual ILD-alone RFs were distributed and amorphous, but consistently showed that the ILD spectrum is facilatory at the cell's best location and inhibitory above and/or below. Prior results have suggested that an IC cell's spatial specificity is generated by summing inputs which are narrowly tuned to frequency and selective for both ILD and ITD. Based on this premise, we present a developmental model which, when trained solely on a cell's true spatial RF, reproduces both the cell's true RF and its ILD-alone RF. According to the model, the connectivity between a space-tuned IC cell and its frequency-specific inputs develops subject to two constraints: the cell must be excited by ILD spectra from the cell's best location and inhibited by spectra from locations above and below but along the vertical strip defined by the best ITD. To assess how frequency-specific inputs are integrated to form restricted spatial RFs, we measured the responses of 47 space-tuned IC cells to pure tones at varying ILDs and frequencies. ILD tuning varied with frequency. Further, pure-tone responses, summed according to the head-related filters, accounted for 56 percent of the variance in broadband ILD-alone RFs. Modelling suggests that, with broadband sounds, cells behave as though they are linearly summing their inputs, but when testing with pure tones, non-linearities arise. This dissertation includes unpublished co-authored materials.

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This research was designed to investigate the fundamental nature in which blind people utilize audible cues to attend to their surroundings. Knowledge on how blind people respond to external spatial stimuli is expected to assist in development of better tools for helping people with visual disabilities navigate their environment. There was also interest in determining how blind people compare to sighted people in auditory localization tasks. The ability of sighted individuals, blindfolded individuals, and blind individuals in localizing spatial auditory targets was assessed. An acoustic display board allowed the researcher to provide multiple sound presentations to the subjects. The subjects’ responses in localization tasks were measured using a combination of kinematic head tracking and eye tracking hardware. Data was collected and analyzed to determine the ability of the groups in localizing spatial auditory targets. Significant differences were found among the three groups in spatial localization error and temporal patterns.

Professional research project (Au.D.)--University of SouthFlorida, 2002. / Title from PDF of title page. / Document formatted into pages; contains 22 pages. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: The purpose of this study was to determine the prevalence of the binaural interaction component (BIC) in a large sample of normal hearing adults, and to measure the absolute latency and amplitude of the BIC as a function of the click rate of the stimulus and the electrode montage. The BIC is obtained by subtracting the auditory evoked potential waveform obtained with binaural stimulation from the waveform obtained by adding the responses from the left and right monaural stimulation. The tested hypothesis was that the recordings of the BIC vary among normal hearing individuals, and BIC latency and amplitude values change as a function of stimulus rate. Studies of the BIC help to explain the neural correlates of some binaural processes, and to develop an electrophysiological index of binaural processes for objective clinical evaluations.Data was completed and analyzed on 47 adults between the ages of 20 and 41 (mean = 25) with hearing in the normal range (thresholds [ 20 dB HL at 500, 1000, 2000, and 4000 Hz in each ear) and no known neurological disorders. The results revealed a great variability in BIC morphology between subjects. The BIC waveforms were categorized into five distinct groups according to the number of positive and negative peaks present. Chi-square analyses revealed a significant relationship between click rate and BIC category; however, the relationship between recording montage and BIC category was insignificant. An Analysis of Variance (ANOVAs) revealed a significant increase in absolute latency and decrease in absolute amplitude of both negative and positive peaks as click rate increased from 7.7/s to 57.7/s. The results did not reveal a significant change in the type of BIC as an effect of electrode montage.In conclusion, the BIC within the binaural difference waveform may be obtained in the majority of young individuals with normal hearing. Specifically, a slower stimulus rate revealed more components of the waveform, as well as an improvement in the morphology of the BIC compared to a faster stimulus rate. As these findings may aid in the development of an electrophysiological index of binaural neural processes in young individuals with normal hearing, more research should be attempted in the study of BIC in other age groups and patients with different audiograms. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.

Virtual three-dimensional auditory displays (V3DADs) use digital signal processing to deliver sounds (typically through headphones) that seem to originate from specific external spatial locations. This set of studies investigates the delivery of V3DADs through bone-conduction transducers (BCTs) in addition to conventional headphones. Although previous research has shown that spatial separation can be induced through BCTs, some additional signal adjustments are required for optimization of V3DADs, due to the difference in hearing pathways. The present studies tested a bone-conduction adjustment function (BAF) derived from equal-loudness judgments on pure tones whose frequencies were spaced one critical band apart. Localization performance was assessed through conventional air-conduction headphones, BCTs with only transducer correction, and BCTs with a BAF. The results showed that in the elevation plane, the BAF was effective in restoring the spectral cues altered by the bone-conduction pathway. No evidence for increased percept variability or decreased lateralization in the bone-conduction conditions was found. These findings indicate that a V3DAD can be implemented on a BCT and that a BAF will improve performance, but that there is an apparent performance cost that cannot be addressed with BAFs measured using the methodology in the present studies.