Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / This study stems from reports in the experimental literature that selective destruction of portions of the ventral acoustic system of the medulla produced differential effects on sound-based behavior. It has been shown that destruction of the nucleus of the trapezoid body or its afferent fibers resulted in a decrement in the strength of responding which terminated an intense noise signal. whereas auditory threshold to noise was not significantly affected. Bxtensive destruction of all the nuclear and fiber components of the ventral acoustic system raised the threshold substantially and produced a reduction in responding on the noise-termination task. The two problems approached in this thesis were to discover other aspects of audition which would be differentially affected by destruction of selected portions of the ventral acoustic system. and to define precisely the neural damage required to produce substantial shifts in auditory threshold. The subjects were albino rats. The experimental chamber was a wire mesh cage which contained a lever and food cup. A loudspeaker and light source were mounted on the roof of the cage. This apparatus and a pellet dispenser were enclosed in a sound-resistant, light-proof bax. [TRUNCATED] / 2031-01-01

Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.

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When a formant transition (isolated transition) and the remainder (base) of a synthesized syllable are presented to opposite ears most subjects perceive two simultaneous sounds, a syllable and a nonspeech chirp. The isolated transition determines the identity of the syllable at one ear and, at the same time, is perceived as a chirp at the opposite ear. This phenomenon, called duplex perception, has been interpreted as the result of the independent operation of two perceptual modes, the phonetic and the auditory mode. In order to test this hypothesis, the isolated transition was preceded and followed by a series of identical transitions sent to the same ear. This streaming procedure weakened the contribution of the transition to the perceived phonetic identity of the syllable. This weakening effect could have been explained in terms of the habituation of an hypothetical phonetic feature detector sensitive to the repetition of identical transitions. For this reason, the same effect was replicated by capturing the isolated transition with others which were aligned on the same frequency-by-time trajectory as the isolated one. These findings are consistent with the idea that the integration of the transition with the base was affected by the operation of general-purpose auditory processes. This contrasts with the hypothesis that the phonetic mode integrated the dichotic stimuli independently of the auditory mode.

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This thesis is composed of two independent manuscripts for publication. The first (Chapter 2) “More Detectable, Less Annoying. The Role of Temporal Variation in Envelope and Spectral Content on Detection and Annoyance” will be submitted to Psychological Science. This manuscript explores how detection and annoyance of sound are affected by temporal variation in two acoustic parameters; amplitude envelope and spectral content. The second (Chapter 3) “Improving Detectability of Auditory Interfaces Through Temporal Variation in Envelope” will be submitted to Human Factors. Here I build off of the previous manuscript by investigating tone detection in a split attention task more pertinent to the normative use of auditory interfaces. The author of this thesis is the primary author of both papers. / Thesis / Master of Science (MSc)

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. / Doctor of Philosophy / 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 sound localization performance. Promisingly, recent studies have exhibited the ability of the human auditory system to learn by demonstrating that training can improve sound localization ability while wearing HPDs. As a result, the U.S. military identified the need for a portable system capable of improving sound localization performance 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 similar sounds as the DRILCOM system. Phase II used a within-subjects human factors experiment to validate whether the PALAT system could impart similar sound 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 HPDs. 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.

Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Neuroanatomical work has shown that the auditory system is different in different mammals, with primates and bats representing two extremes in this regard. It has been suggested that these differences are related to auditory localization. The present work examined auditory localization in several representative mammalian speciesa squirrel monkey, bat {Phyllostomus hastatus), albino rat and cat. A semi-naturalistic localization situation was used. The animal was placed in a wire cage located in a sound-deadened room. Two loudspeakers were located one on either side of the cage. Two response lavers were located in the front wall of the cage, flanking a liquid food dispenser. When tone bursts were presented from one of the loudspeakers, a response on the "correct" lever resulted in the delivery of a small amount of food to the animal. The left-hand lever was correct when the tone bursts were from the left-hand loudspeaker, the right-hand lever was correct when the tone bursts were from the right-hand loudspeaker. The percentage of correct responses on both levers was the measure of performance on the discrimination under a given set of conditions. [TRUNCATED] / 2031-01-01

Once the sound reaches the ear, hearing can no longer be exclusively described as a me- chanical phenomenon of wave propagation. As we follow the auditory pathways deeper into the brain, neuronal action potentials shape our perception of sound. But how exactly do the spectrotemporal characteristics of the sound wave a ect perception? We investigated human auditory perception and decisional behaviour with reverse correlation. This technique yields richer datasets than classical methods based on performance metrics alone, providing classi - cation images (CIs) that display observers' task-dependent strategies while potentially serving as templates for computational modeling. We found that observers use the same strategies to detect peaks and dips in sound pressure on a narrow time scale but rst and second-order CIs reveal di erent temporal dynamics within each strategy. When observers detected a speci c frequency on a similar timescale, we were able to expose signatures of neuronal-like spectrotemporal tuning. Detailed modeling of the results showed that observers were not able to rely on the explicit output of these channels. In auditory motion experiments, CIs presented distinct spectrotemporal dynamics between sounds moving from one side of the observer to the other and sound moving towards or away from the observer. In stark contrast, an artificial detector program returned identical CIs. When stimuli were embedded in fragments of human speech and natural sounds, observers used a knowledge- based strategy; as long as fragments were perceived as meaningful, CIs displayed robust tuning e ects which diminished when speech was presented in a temporally reversed order. Overall, we can conclude that reverse correlation is a powerful tool for probing the human auditory system. It reflects task-dependent strategies imposed by the underlying neuronal circuitry rather than statistics or task speci cation.

For individuals with Autism Spectrum Disorder or ‘ASD’ the ability to accurately process and interpret auditory information is often difficult. Here we review behavioural, neurophysiological and neuroimaging literature pertaining to the field of auditory processing in ASD, with the aim of providing a comprehensive account of auditory processing in this population and thus an effective tool to aid further research. Literature was sourced from peer-reviewed journals published over the last two decades which best represent research conducted in these areas. Findings show substantial evidence for atypical processing of auditory information in ASD. Behavioural studies provide support for widespread abnormalities ranging from atypical perception of various low-level perceptual features (i.e. pitch) to processing of more complex auditory information such as prosody. Magnetic resonance imaging studies have identified functional abnormalities to a range of auditory stimuli in ASD while structural abnormalities have been observed in several brain regions implicated in auditory processing. Electrophysiological research has found evidence for atypical auditory processing within the cortex and brainstem of individuals with ASD in a variety of experimental paradigms. Trends across studies suggest auditory processing impairments in ASD are more likely to present during processing of complex auditory information and are more severe for speech than for non-speech stimuli. Moreover, atypical auditory processing in ASD may not always be viewed as an impairment and in some cases may reflect the use of a compensatory strategy to make sense of auditory information. To this end, there is an urgent need for further research aimed at understanding the behavioural and neural basis of auditory processing in ASD.