Browsing by Author "Lee, Kichol"

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    Development and Human Factors Evaluation of a Portable Auditory Localization Acclimation Training System
    Thompson, Brandon Scott (Virginia Tech, 2020-06-19)
    Auditory situation awareness (ASA) is essential for safety and survivability in military operations where many of the hazards are not immediately visible. Unfortunately, the Hearing Protection Devices (HPDs) required to operate in these environments can impede auditory localization performance. Promisingly, recent studies have exhibited the plasticity of the human auditory system by demonstrating that training can improve auditory localization ability while wearing HPDs, including military Tactical Communications and Protective Systems (TCAPS). As a result, the U.S. military identified the need for a portable system capable of imparting auditory localization acquisition skills at similar levels to those demonstrated in laboratory environments. The purpose of this investigation was to develop and validate a Portable Auditory Localization Acclimation Training (PALAT) system equipped with an improved training protocol against a proven laboratory grade system referred to as the DRILCOM system and subsequently evaluate the transfer-of-training benefit in a field environment. In Phase I, a systems decision process was used to develop a prototype PALAT system consisting of an expandable frame housing 32-loudspeakers operated by a user-controlled tablet computer capable of reproducing acoustically accurate localization cues similar to the DRILCOM system. Phase II used a within-subjects human factors experiment to validate whether the PALAT system could impart similar auditory localization training benefits as the DRILCOM system. Results showed no significant difference between the two localization training systems at each stage of training or in training rates for the open ear and with two TCAPS devices. The PALAT system also demonstrated the ability to detect differences in localization accuracy between listening conditions in the same manner as the DRILCOM system. Participant ratings indicated no perceived difference in localization training benefit but significantly preferred the PALAT system user interface which was specifically designed to improve usability features to meet requirements of a user operable system. The Phase III investigation evaluated the transfer-of-training benefit imparted by the PALAT system using a broadband stimulus to a field environment using gunshot stimulus. Training under the open ear and in-the-ear TCAPS resulted in significant differences between the trained and untrained groups from in-office pretest to in-field posttest.
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    Effects of Earplug Material, Insertion Depth, and Measurement Technique on Hearing Occlusion Effect
    Lee, Kichol (Virginia Tech, 2011-01-21)
    Occlusion effects result from amplification of low frequency components of body- transmitted sound when the ear canal is occluded with hearing protection devices, hearing aids, or other canal-sealing inserts. Since the occlusion effect will enhance the hearing of bodily- generated sounds and result in distorted perception of one's own voice, many people report annoyance with hearing aids and hearing protectors that produce occlusion effects. Previous research has studied the effects of ear device insertion depth and influence of the location of the bone vibrator, which has typically been used as the excitation stimulus. However, the effects of monaural vs. binaural, ear device material, and different excitation stimuli were not investigated. In this research study, the effect of left/right ear canal on the occlusion effect, which was measured objectively as the sound pressure level difference in dB, was investigated. Also, an experiment to determine the effect of earplug types (differing in material and design), insertion depth, and excitation sources was conducted. Lastly, the noise attenuation capability of medical balloon-based earplugs was tested. Ten subjects, six male and four female, volunteered for the three separate experiments. They were subjected to the three earplug types (foam earplugs, premolded flanged earplugs, and medical balloon-based earplugs), two earplug insertion depth levels of shallow and deep (only feasible with the foam earplug and the balloon-based earplug), and two levels of excitation sources, one of which was a forehead-mounted bone vibrator and the other a self vocal utterance of "EE" to 65 decibels A-weighted (dBA). The attenuation capability of the medical balloon- based earplugs were tested via monaural Real-Ear-Attenuation-at-Threshold (REAT) test per ANSI S3.19-1974 and compared to that of a Peltor H10A earmuff. Experimental results of the first experiment demonstrated that left right ear canal SPL measurements were not statistically different, and therefore subsequent measurements of occlusion effects for the second experiment were conducted via a monaural left ear measurement protocol. The results of the second experiment confirmed significant effects of insertion depth on the occlusion effect. At the shallow insertion, the occlusion effects, on average, were greater by 11.2 dB(linear) (dBZ) then the deep insertion measured at 500 Hz. The effects of earplug type were mixed. At the shallow insertion, earplug type did not influence the occlusion effect. However, the mean occlusion effect, measured at the 1/3-octave band centered at 500 Hz, of deeply inserted balloon-based earplugs was larger than that of foam earplugs by 3.7 dBZ. Excitation sources that were used as the sound energy stimuli to elicit occlusion effects did not show statistically significant differences. The Noise Reduction Rating (NRR), as calculated per ANSI S3.19-1974, of the medical balloon-based earplug was 10 dB while that of a Peltor H10A earmuff was 24 dB. Although the medical balloon-based earplug did not prove to be a high attenuation-hearing protector, it produced a unique flat attenuation across the frequency spectrum, as compared to the typical increasing-with-frequency attenuation, pointing to its potential utility for applications wherein the pitch perception of sound is important.
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    Effects of Sound on Postural Stability during Quiet Standing
    Park, Sung H; Lee, Kichol; Lockhart, Thurmon E.; Kim, Sukwon (2011-12-15)
    Loss of postural stability can increase the likelihood of slips and falls in workplaces. The present study intended to extend understanding of the effects of frequency and pressure level of sound on postural stability during standing. Eleven male subjects participated. Standing on a force platform, the subjects' center of pressures were measured under different combinations of pressure level and frequency of the sound. Variables such as the position variability of COP and the length of postural sway path in anterior-posterior (AP) and medio-lateral (ML) direction were evaluated. Subjective ratings of perceived disturbance at each experimental condition were also obtained using a 7-point rating scale. Results showed that the length of sway path and the position variability of COP increased as the frequency of sound increased in posterior-anterior axis. The effect of sound pressure level, however, was not significant on both the postural sway length and the position variability of COP. These results suggested substantial disturbance of standing balance system among subjects exposed to high frequency noise. The results implied that physical workers should be alerted that their abilities of postural balance could be degraded significantly as disturbance caused by a sound existed.
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    Evaluation of an Auditory Localization Training System for Use in Portable Configurations: Variables, Metrics, and Protocol
    Cave, Kara Meghan (Virginia Tech, 2020-01-22)
    Hearing protection can mitigate the harmful effects of noise, but for Service Members these devices can also obscure auditory situation awareness cues. Tactical Communication and Protective Systems (TCAPS) can restore critical cues through electronic circuitry with varying effects on localization. Evidenced by past research, sound localization accuracy can improve with training. The investigator hypothesized that training with a broadband stimulus and reducing the number of presentations would result in training transfer. Additionally, training transfer would occur with implementation of more user-engaged training strategies. The purpose of the experiments described in this study was to develop an optimized auditory azimuth-training protocol for use in a field-validated portable training system sensitive to differences among different TCAPS. A series of indoor experiments aimed to shorten and optimize a pre-existing auditory localization training protocol. Sixty-four normal-hearing participants underwent localization training. The goal of training optimization included the following objectives: 1) evaluate the effects of reducing stimulus presentations; 2) evaluate the effects of training with a broadband stimulus (but testing on untrained military-relevant stimuli); and 3) evaluate performance differences according to training strategies. Twenty-four (12 trained and 12 untrained) normal-hearing listeners participated in the field-validation experiment. The experiment evaluated localization training transfer from the indoor portable system to live-fire blanks in field. While training conducted on the portable system was predicted to transfer to the field, differences emerged between an in-the-ear and over-the-ear TCAPS. Three of four untrained stimuli showed evidence of training transfer. Shortening the training protocol also resulted in training transfer, but manipulating training strategies did not. A comparison of changes in localization scores from the indoor pretest to the field posttest demonstrated significant differences among listening conditions. Training improved accuracy and response time for the open ear and one of two TCAPS. Posttest differences between the two TCAPS were not statistically significant. Despite training, localization with TCAPS never matched the open ear. The portable apparatus employed in this study offers a means to evaluate the effects of TCAPS on localization. Equipped with a known effect on localization, TCAPS users can render informed decisions on the benefits or risk associated with certain devices.
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    Method and structure for achieving spectrum-tunable and uniform attenuation
    (United States Patent and Trademark Office, 2013-10-08)
    The present invention relates hearing protection devices for the human ear. More particularly, embodiments of the invention provide hearing protection devices capable of tunable acoustic attenuation. The invention relates further to ear plugs comprising a fluid-containing balloon for occlusion of the ear canal, which are capable of being adjusted for example by modifying fluid composition and/or fluid pressure within the balloon to vary attenuation at different frequencies of the audible sound spectrum. Other embodiments provide an earplug with fixed attenuation comprising: a body of compressible/expandable-recovery material shaped and sized to fit in an ear canal; and at least one chamber disposed within the body and comprising a filler material chosen from at least one of water, aphrons, water with solid or gelatinous particles suspended, and oil with particles suspended.
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    A virtual look at Epstein-Barr virus infection: Biological interpretations
    Duca, Karen A.; Shapiro, Michael; Delgado-Eckert, Edgar; Hadinoto, Vey; Jarrah, Abdul Salam; Laubenbacher, Reinhard C.; Lee, Kichol; Luzuriaga, Katherine; Polys, Nicholas F.; Thorley-Lawson, David A. (PLOS, 2007-10-19)
    The possibility of using computer simulation and mathematical modeling to gain insight into biological and other complex systems is receiving increased attention. However, it is as yet unclear to what extent these techniques will provide useful biological insights or even what the best approach is. Epstein -Barr virus (EBV) provides a good candidate to address these issues. It persistently infects most humans and is associated with several important diseases. In addition, a detailed biological model has been developed that provides an intricate understanding of EBV infection in the naturally infected human host and accounts for most of the virus' diverse and peculiar properties. We have developed an agent-based computer model/ simulation (PathSim, Pathogen Simulation) of this biological model. The simulation is performed on a virtual grid that represents the anatomy of the tonsils of the nasopharyngeal cavity (Waldeyer ring) and the peripheral circulation -the sites of EBV infection and persistence. The simulation is presented via a user friendly visual interface and reproduces quantitative and qualitative aspects of acute and persistent EBV infection. The simulation also had predictive power in validation experiments involving certain aspects of viral infection dynamics. Moreover, it allows us to identify switch points in the infection process that direct the disease course towards the end points of persistence, clearance, or death. Lastly, we were able to identify parameter sets that reproduced aspects of EBV-associated diseases. These investigations indicate that such simulations, combined with laboratory and clinical studies and animal models, will provide a powerful approach to investigating and controlling EBV infection, including the design of targeted anti-viral therapies.