Dissertations / Theses: 'Cochlear mechanics'

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Sun, Luyang. "Inverse methods in cochlear mechanics." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/413460/.

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Cochlear modelling is used to provide insight into the physical mechanics of the cochlea. The complicated, three dimensional geometry of the fluid chambers in the cochlea is often represented in models of its mechanics by a box with a uniform area along its length. The first part of this thesis is concerned with the development of a tapered box model of the cochlea, in which the geometry of the cochlea is assumed to vary in a linear way along its length. Previous measurements of the variation in area of the two fluid chambers along the length of the cochlea in various mammals has been used to calculate a linear fit to the variation in the "effective area" that determines the 1D fluid coupling. The width of the basilar membrane is also assumed to vary linearly along the length of the model. The analytic form of the 1D fluid pressure distribution due to elemental BM motion is derived for this tapered box model, together with the added mass due to near field acoustic coupling. The coupled response in the 1D and 3D, uniform and tapered box model of passive cochlea can then be readily calculated. Although the form of the fluid coupling are very different in the uniform and tapered box models, the distribution of the basilar membrane vibration in the coupled models are very similar. The second part of the thesis is concerned with deriving the parameters of cochlear models from measured data using inverse methods. Previous inverse methods are first reviewed before a novel direct method is introduced, based on modelling the poles and zeros of the micromechanical response. This is compared with other inverse methods, using previously measured data on basilar membrane vibration in the cochlea, and relatively simple models are shown to provide a good fit to the data.

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Kolston, Paul Johannes. "Towards a better understanding of cochlear mechanics: A new cochlear model." Thesis, University of Canterbury. Electrical and Electronic Engineering, 1989. http://hdl.handle.net/10092/6653.

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Improving our understanding of cochlear mechanics requires the analysis of cochlear models. In the formulation of such models, it is necessary to make assumptions as to the relative importance of the many structures which comprise the cochlear partition. Data on the relative motion of these structures are virtually non-existent, and so the accuracy of many of the assumptions made is questionable. The bulk of the content of this thesis relates to the formulation and analysis of a new type of linear mechanical cochlear model. The new assumptions made in the formulation of the model are justified on the basis of the structure of the cochlear partition. The apparent realism of the model (both its structure and certain features of its response) seriously questions the hypothesis that response tuning and changes in response resulting from trauma prove the existence of active processes in the cochlea. Furthermore, arguments are presented that question the validity of using the presence of spontaneous otoacoustic emissions to justify the existence of active processes in cochlear tuning. The new model suggests that the complicated structural geometry of the cochlear partition (particularly the organ of Corti) must be incorporated in a model before conclusions relating to real cochlear behaviour can be drawn from it. In particular, the model suggests that a mechanical second filter exists in the cochlea, from rather broad tuning in the pectinate zone of the basilar membrane to sharper, neural-like tuning in the arcuate zone. It is concluded that the only way to properly check the validity of cochlear models is to obtain more experimental data pertaining to the relative motions of the various components that constitute the cochlear partition. Before this is done, we should not place too much faith in our present (alleged) understanding of cochlear mechanics. Also presented in this thesis are new modelling techniques for improving the realism of electrical transmission line cochlear models: the ability to include longitudinal and radial mechanical coupling, multidimensional fluid motion and stick-slip friction. It is shown that the inclusion of mechanical coupling and two-dimensional fluid motion in the new cochlear model has a predictable (and trivial) effect on-its response. The use of the stick-slip friction modelling technique is illustrated by means of two simple examples.

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Watts, Lloyd Mead Carver. "Cochlear mechanics : analysis and analog VLSI /." Diss., Pasadena, Calif. : California Institute of Technology, 1993. http://resolver.caltech.edu/CaltechETD:etd-07022004-115127.

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4

Bell, James Andrew, and andrew bell@anu edu au. "The Underwater Piano: A Resonance Theory of Cochlear Mechanics." The Australian National University. Research School of Biological Sciences, 2006. http://thesis.anu.edu.au./public/adt-ANU20080706.141018.

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This thesis takes a fresh approach to cochlear mechanics. Over the last quarter of a century, we have learnt that the cochlea is active and highly tuned, observations suggesting that something may be resonating. Rather than accepting the standard traveling wave interpretation, here I investigate whether a resonance theory of some kind can be applied to this remarkable behaviour.¶ A historical survey of resonance theories is first conducted, and advantages and drawbacks examined. A corresponding look at the traveling wave theory includes a listing of its short-comings.¶ A new model of the cochlea is put forward that exhibits inherently high tuning. The surface acoustic wave (SAW) model suggests that the three rows of outer hair cells (OHCs) interact in a similar way to the interdigital transducers of an electronic SAW device. Analytic equations are developed to describe the conjectured interactions between rows of active OHCs in which each cell is treated as a point source of expanding wavefronts. Motion of a cell launches a wave that is sensed by the stereocilia of neighbouring cells, producing positive feedback. Numerical calculations confirm that this arrangement provides sharp tuning when the feedback gain is set just below oscillation threshold.¶ A major requirement of the SAW model is that the waves carrying the feedback have slow speed (5-200 mm/s) and high dispersion. A wave type with the required properties is identified - a symmetric Lloyd-Redwood wave (or squirting wave) - and the physical properties of the organ of Corti are shown to well match those required by theory.¶ The squirting wave mechanism may provide a second filter for a primary traveling wave stimulus, or stand-alone tuning in a pure resonance model. In both, cyclic activity of squirting waves leads to standing waves, and this provides a physical rendering of the cochlear amplifier. In keeping with pure resonance, this thesis proposes that OHCs react to the fast pressure wave rather than to bending of stereocilia induced by a traveling wave. Investigation of literature on OHC ultrastructure reveals anatomical features consistent with them being pressure detectors: they possess a cuticular pore (a small compliant spot in an otherwise rigid cell body) and a spherical body within (Hensens body) that could be compressible. I conclude that OHCs are dual detectors, sensing displacement at high intensities and pressure at low. Thus, the conventional traveling wave could operate at high levels and resonance at levels dominated by the cochlear amplifier. ¶ The latter picture accords with the description due to Gold (1987) that the cochlea is an underwater piano - a bank of strings that are highly tuned despite immersion in liquid.¶ An autocorrelation analysis of the distinctive outer hair cell geometry shows trends that support the SAW model. In particular, it explains why maximum distortion occurs at a ratio of the two primaries of about 1.2. This ratio also produces near-integer ratios in certain hair-cell alignments, suggesting that music may have a cochlear basis.¶ The thesis concludes with an evaluation and proposals to experimentally test its validity.

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Ryan, Marie Siobhan. "The influence of neural activity on cochlear mechanics in humans." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404594.

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Sellon, Jonathan Blake. "The functional role of tectorial membrane poroelasticity in cochlear mechanics." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107287.

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Thesis: Ph. D., Harvard-MIT Program in Health Sciences and Technology, 2016.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 121-132).
The tectorial membrane (TM) is an extracellular matrix that overlies the mechanically sensitive hair bundles of sensory receptor cells in the inner ear. Based on this strategic position, it has long been accepted that the TM plays a critical role in the stimulation of sensory hair cells. Early measurements demonstrated elastic properties of the TM and suggested that the TM is resonant. More recent measurements have shown that longitudinal coupling of the TM generates traveling waves that contribute to cochlear tuning. Here we show the importance of (1) viscosity in controlling the spread of excitation in TM traveling waves, as well as the importance of matrix porosity in determining (2) the viscosity of genetically modified TMs, and (3) local interactions with hair bundles. To understand the longitudinal spread of mechanical excitation via TM traveling waves, we develop chemical manipulations that systematically and reversibly alter TM stiffness and viscosity. Increasing TM viscosity or decreasing stiffness reduces longitudinal spread of mechanical excitation, thereby coupling a smaller range of best frequencies, which would sharpen tuning. In contrast, increasing viscous loss or decreasing stiffness would tend to broaden tuning in resonance based TM models. Thus, TM wave and resonance mechanisms are fundamentally different in the way they control frequency selectivity. To understand the molecular origin of TM viscosity, we investigate traveling waves in genetically modified TMs. We show that nanoscale pores of TectaY1870C/+ TMs are significantly larger than those of Tectb -/- TMs. The larger pore size reduces shear viscosity, thereby reducing traveling wave speed and increasing spread of excitation. These results demonstrate the previously unrecognized importance of TM porosity in cochlear tuning. To understand how TM porosity affects the local interaction between the TM and hair cells, we apply oscillatory forces to the TM with spherical probe tips. The effective stiffness of the TM is small at low frequencies where the porous matrix and surrounding fluid can move independently. By contrast, the effective stiffness of the TM is large at high frequencies, where these two phases are entrained by viscosity to move together. Interestingly, the transition frequency is in the audio frequency range only for hair bundle sized tips. Furthermore, the transition region is characterized by increased phase lead between the stimulus force and applied displacement that may play an essential role in the stability of micromechanical feedback paths and ultimately the sensitivity of hearing. In conclusion, these results show that traveling wave properties and local interactions with the hair bundles depend critically on TM porosity, thus fundamentally changing the way we think about molecular mechanisms underlying cochlear frequency selectivity and sensitivity.
by Jonathan Blake Sellon.
Ph. D.

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Williams, Deirdre Mary. "The effect of the auditory efferents on acoustic distortion products in human subjects." Thesis, University of Sussex, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240554.

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Arcand, Benjamin Y. "An active surgical positioning device for a cochlear implant electrode array /." Available online. Click here, 2005. http://sunshine.lib.mtu.edu/ETD/DISS/arcandb/diss.pdf.

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9

Ghaffari, Roozbeh 1979. "The functional role of the mammalian tectorial membrane in the cochlear mechanics." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/43876.

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Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2008.
Includes bibliographical references (p. 101-110).
Sound-evoked vibrations transmitted into the mammalian cochlea produce traveling waves that provide the mechanical tuning necessary for spectral decomposition of sound. These traveling waves of motion propagate along the basilar membrane (BM) and ultimately stimulate the mechano-sensory receptors. The tectorial membrane (TM) plays a key role in this stimulation process, but its mechanical function remains unclear. Here we show that the TM supports traveling waves that are an intrinsic feature of its visco-elastic structure. Radial forces applied at audio frequencies (1-20 kHz) to isolated TM segments generate longitudinally propagating waves on the TM with velocities similar to those of the BM traveling wave near its best frequency (BF) place. We compute the dynamic shear storage modulus and shear viscosity of the TM from the propagation velocity of the waves and show that segments of the TM from the basal turn are stiffer than apical segments are. Analysis of loading effects of hair bundle stiffness, the limbal attachment of the TM, and viscous damping in the subtectorial space suggests that TM traveling waves can occur in vivo. To test how TM waves may participate in cochlear function, we investigated waves in genetically modified mice lacking beta-tectorin, a glycoprotein found exclusively in the TM. Tectb-/- mutant mice were previously shown to exhibit significant loss of cochlear sensitivity at low frequencies and sharpened frequency tuning compared to wild types. We show that the spatial extent and propagation velocity of TM traveling waves are significantly reduced in Tectb-/- mice compared to wild types, consistent with the concept that there is a reduction in the spread of excitation via TM waves and less TM wave interaction with the BM traveling wave in Tectb-/- mice.
(cont.) The differences in TM wave properties between mutants and wild types arise from changes to the mechanical properties of the TM; mutant TMs are significantly less stiff than wild type TMs are. Our results show the presence of a traveling wave mechanism through the TM that can functionally couple a significant longitudinal extent of the cochlea and may interact with the BM wave, suggesting that TM waves are crucial for cochlear sensitivity and tuning.
by Roozbeh Ghaffari.
Ph.D.

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Hill, Jennifer Clare. "The relationship between auditory efferent function and frequency selectivity in man." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313735.

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11

Murugasu, Euan. "In-vivo measurements of basilar membrane displacement in the basal turn of the guinea pig cochlea : evidence for the role of outer hair cells in active cochlear mechanics." Thesis, University of Sussex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318941.

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12

Saremi, Amin G. "Effects of Specific Cochlear Pathologies on the Auditory Functions : Modelling, Simulations and Clinical Implications." Doctoral thesis, Linköpings universitet, Avdelningen för neurovetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-105810.

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A hearing impairment is primarily diagnosed by measuring the hearing thresholds at a range of auditory frequencies (air-conduction audiometry). Although this clinical procedure is simple, affordable, reliable and fast, it does not offer differential information about origins of the hearing impairment. The main goal of this thesis is to quantitatively link specific cochlear pathologies to certain changes in the spectral and temporal characteristics of the auditory system. This can help better understand the underlying mechanisms associated with sensorineural hearing impairments, beyond what is shown in the audiogram. Here, an electromechanical signal-transmission model is devised in MATLAB where the parameters of the model convey biological interpretations of mammalian cochlear structures. The model is exploited to simulate the cell-level cochlear pathologies associated with two common types of sensorineural hearing impairments, 1: presbyacusis (age-related hearing impairment) and, 2: noise-induced hearing impairment. Furthermore, a clinical study, consisting of different psychoacoustic and physiological tests, was performed to trace and validate the model predictions in human. The results of the clinical tests were collated and compared with the model predictions, showing a reasonable agreement. In summary, the present model provides a biophysical foundation for simulating the effect of specific cellular lesions, due to different inner-ear diseases and external insults, on the entire cochlear mechanism and thereby on the whole auditory system. This is a multidisciplinary work in the sense that it connects the ‘biological processes’ with ‘acoustic modelling’ and ‘clinical audiology’ in a translational context.

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Howard, MacKenzie A. "Mechanisms of inhibition in the avian cochlear nucleus /." Thesis, Connect to this title online; UW restricted, 2008. http://hdl.handle.net/1773/10551.

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Tobin, Mélanie. "Gradients in the mechanical properties of auditory hair cells." Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC183/document.

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Notre capacité à communiquer et à apprécier la musique repose sur une discrimination de fréquences couvrant une large gamme de fréquences sonores. Cette propriété résulte de cellules mécanosensorielles « ciliées », qui sont réglées pour répondre de façon maximale à une fréquence caractéristique qui varie monotoniquement le long de l’axe de l’organe auditif, la cochlée. Les mécanismes cellulaires et moléculaires qui définissent la fréquence d’une cellule ciliée et régulent sa valeur pour différentes cellules afin de couvrir la gamme auditive demeurent néanmoins inconnus. Notre hypothèse de travail est que cette fréquence est réglée en partie par les propriétés mécaniques passives et actives de la « touffe ciliaire », l’antenne mécanosensorielle de la cellule ciliée. A l’aide d’une préparation excisée de la cochlée du rat, nous avons combiné l’iontophorèse de chélateurs de calcium (BAPTA ou EDTA) pour casser les liens de bout-de-cil qui connectent les stéréocils voisins de la touffe ciliaire, une stimulation grâce à un micro-jet de fluide pour estimer la raideur de la touffe ciliaire et des enregistrements en « patch-clamp » de courants de transduction afin de compter le nombre de liens de bout-de-cil intacts qui contribuent à la réponse. Avec les mouvements évoqués par la rupture des liens de bout-de-cil et avec nos mesures de raideur, nous avons pu estimer la tension dans toute la touffe ciliaire, ainsi que la tension dans un seul lien de bout-de-cil en connaissant le nombre de liens qui contribuent à cette tension. Dans les cellules ciliées externes, qui sont impliquées dans l’amplification du stimulus sonore mais qui n’envoient pas d’information neuronale au cerveau, nous avons observé un gradient de tension et de raideur lorsque la fréquence caractéristique de la cellule ciliée augmente, suggérant que ces paramètres physiques peuvent être impliqués dans le réglage d’une cellule ciliée à sa fréquence caractéristique. Au contraire, pour les cellules ciliées internes, les vraies cellules sensorielles de la cochlée, nos observations ne montrent pas de gradient significatif. De plus, nous avons observé des mouvements de la touffe ciliaire induits par la variation de la concentration en calcium, correspondant à une tension accrue pour des concentrations en calcium plus faibles. Ces mouvements sont similaires à ceux évoqués dans d’autres classes de vertébrés, tels que chez la grenouille ou chez la tortue. Ainsi, nos résultats réconcilient les expériences faites chez les vertébrés inférieurs et chez le mammifère, et montrent l’implication des gradients de la mécanique de la touffe ciliaire pour l’importante sélectivité fréquentielle de la cochlée
Our ability to communicate and appreciate music relies on acute frequency discrimination over a broad range of sound frequencies. This property results from the operation of mechanosensory “hair" cells, which are each tuned to respond maximally to a characteristic frequency that varies monotonically along the axis of the auditory organ, the cochlea. The cellular and molecular mechanisms that set the characteristic frequency of a hair cell and regulate its value among different cells to cover the auditory range have remained elusive. Our working hypothesis is that tuning results in part from passive and active mechanical properties of the “hair" bundle, the mechanosensory antenna of the hair cell.Using an excised preparation from the rat cochlea, we combined iontophoresis of a calcium chelator (BAPTA or EDTA) to break the tip links that interconnect neighbouring stereocilia of the hair-cell bundle, fluid-jet stimulation to estimate hair-bundle stiffness and patch-clamp recordings of transduction currents to count the number of intact transduction channels contributing to the response. From the movements evoked by tip-link breakage and our stiffness measurements, we were able to estimate tension in the whole hair bundle as well as, knowing the number of tip links contributing to this tension, in a single tip link.In outer hair cells, which are involved in sound amplification but do not send neural information to the brain, we observed a gradient of tension and stiffness from the low-frequency to the high-frequency end of the cochlea, suggesting that these physical parameters may help tune the hair cell to its characteristic frequency. Interestingly, with inner hair cells - the true sensors of the cochlea, our observations do not show any significant gradient. Furthermore, we observed calcium-evoked hair-bundle movements corresponding to an increased tension in the tip links at decreased concentrations of calcium. These movements were similar to those evoked in other classes of vertebrates, such as the frog or the turtle. Together, our results reconcile experiments performed in lower vertebrates with those performed in mammals and show the implication of hair-bundle mechanical gradients in the sharp frequency tuning of the cochlea

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Tong, Mingjie. "Mechanisms underlying subthreshold and suprathreshold responses in dorsal cochler nucleus cartwheel cells /." See Full Text at OhioLINK ETD Center (Requires Adobe Acrobat Reader for viewing), 2005. http://www.ohiolink.edu/etd/view.cgi?toledo1133806721.

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Dissertation (Ph.D.)--University of Toledo, 2005.
Typescript. "A dissertation [submitted] as partial fulfillment of the requirements of the Doctor of Philosophy degree in Engineering." Bibliography: leaves 128-141.

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Tong, Mingjie. "Mechanisms Underlying Subthreshold and Suprathreshold Responses in Dorsal Cochlear Nucleus Cartwheel Cells." University of Toledo / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1133806721.

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17

Lahne, Manuela. "Damage-induced signalling mechanisms in the neonatal rat cochlea." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1444911/.

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Sound overstimulation and exposure to ototoxic drugs damage cochlear hair cells (HCs) and cause their death. The surrounding support cells maintain an epithelial barrier and the appropriate physiological environment for surviving HCs during pathological conditions. Coordination of this homeostatic process requires cellular signalling. However, the signalling events that are activated during damage in the mammalian cochlea, are poorly understood. Neonatal rat cochlear explants were subjected to mechanical damage or exposed to neomycin - an ototoxin. Mechanical damage triggered the immediate propagation of an intercellular wave of increased intracellular Ca2+ from the lesion site into distinct cochlear regions. The properties of the Ca2+ wave and the source of Ca2+ required were specific to the cochlear region. IP3-mediated release from intracellular stores and influx of extracellular Ca2+ contribute differentially to the rise in intracellular Ca2+. The release of extracellular ATP is crucial for the propagation of the damage-induced Ca2+ wave. Gap junctions or connexin hemichannels also contribute to its formation. A subsequent damage-induced signalling event is the transient phosphorylation of ERK1/2 that arises within minutes of the insult occurring in support cells specifically. Similarly to the formation of the Ca2+ wave, release of extracellular ATP and gap junctions are critical for ERK1/2 activation. UTP-induced activation of ERK1/2 reveals the involvement of P2Y receptors. In addition, a requirement for the influx of extracellular Ca2+ also suggests a role for ion channels - potentially P2X receptors. P2X2,3,4 and P2Y2.4, n receptors were expressed in cochlear explants with P2X2 and P2Y2 being exclusive to support cells. Damage-induced currents were recorded from Deiters' cells in a syncytium during mechanical damage of the cochlea. Finally, when HCs were specifically targeted using neomycin, ERK1/2 activation occurred in support cells surrounding pyknotic HC nuclei. Inhibition of ERK1/2 delayed HC death.

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Weddell, Thomas David. "Mechanisms of excitation and amplification in the mammalian cochlea." Thesis, University of Brighton, 2013. https://research.brighton.ac.uk/en/studentTheses/0f9db6ef-c538-4db9-a714-ea04154959fa.

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Mechanisms of cochlea excitation and amplification were investigated experimentally across a range of mammalian species. Distortion product otoacoustic emissions (DPOAEs) are used to clinically assess hearing. DPOAEs recorded from the ears of human subjects in the presence of a low frequency, high level tone were compared with similar recordings made from guinea pigs. Both guinea pig and human data were found to originate from a common cochlear nonlinearity; the Boltzmann model of DPOAE generation at the output of a spatially localised single-saturating non-linearity. Accordingly, the guinea pig cochlea can be used as a human model system for the study of DPOAE generation.

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McMahon, Catherine. "The mechanisms underlying normal spike activity of the primary afferent synapse in the cochlea and its dysfunction : an investigation of the possible mechanisms of peripheral tinnitus and auditory neuropathy." University of Western Australia. School of Biomedical and Chemical Sciences, 2004. http://theses.library.uwa.edu.au/adt-WU2003.0034.

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[Truncated abstract] One of the problems in researching tinnitus is that it has often been assumed that the physiological mechanisms underlying the tinnitus percept cannot be objectively measured. Nonetheless, it is generally accepted that the percept results from altered spontaneous neural activity at some site along the auditory pathway, although it is still debated whether it is produced by: synchronisation of activity of adjacent neurones; a change in the temporal pattern of activity of individual neurones; or an increase in the spontaneous firing rate per se. Similarly, it is possible that the recently coined “auditory neuropathy” is produced by under-firing of the primary afferent synapse, although several other mechanisms can also produce the symptoms described by this disorder (normal cochlear mechanical function but absent, or abnormal, synchronous neural firing arising from the cochlea and auditory brainstem, known as the auditory brainstem response, or ABR). Despite an absent ABR, some subjects can detect pure tones at near-normal levels, although their ability to integrate complex sounds, such as speech, is severely degraded in comparison with the pure-tone audiogram. The aim of the following study was to investigate the normal mechanisms underlying neural firing at the primary afferent synapse, and its regulation, to determine the possible mechanisms underlying over-firing (tinnitus) or under-firing (auditory neuropathy) of primary afferent neurones.

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O'Gorman, David E. "Dynamical mechanisms of neural firing irregularity and modulation sensitivity with applications to cochlear implants." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35513.

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Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2006.
Includes bibliographical references.
The degree of irregularity apparent in the discharge patterns of electrically stimulated auditory-nerve fibers depends upon the stimulation rate. Whereas fibers fire regularly at low stimulation rates, the same fibers fire irregularly at high rates. The irregularity observed at high stimulation rates has been attributed to noise caused by the random open and closing of voltage-gated ion channels. This explanation however is incomplete: an additional mechanism must be operating to account for the different effects of noise at the two stimulation rates. We have identified such an additional rate-dependent mechanism. Specifically, we show in the Fitzhugh-Nagumo (FN) model that the stability to perturbations such as noise depends upon the stimulation rate. At sufficiently high rates a dynamical instability arises that accounts for the main statistical features of the irregular discharge pattern, even in the absence of ongoing physiological noise. In addition, we show that this instability accounts for both the statistical independence exhibited by different fibers in the stimulated population and their sensitivity to amplitude modulations applied to an ongoing stimulus.
(cont.) In cochlear implants, amplitude modulations are used to encode acoustic information such as speech. Psychophysically, sensitivity to small modulations correlates strongly with speech perception, suggesting a critical role for dynamical stability/instability in speech perception. We show that rate-dependent stability/instability occurs in the classical Hodgkin-Huxley model, as well as in biophysical models of the mammalian node of Ranvier.
by David E. O'Gorman.
Ph.D.

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Patra, Harisadhan. "Mechanisms of remote masking." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1199309775.

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Zhao, Wei. "The inhibitory mechanisms of sound processing in the dorsal cochlear nucleus of the guinea pig." Thesis, Keele University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297207.

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Latif, Rhonira. "Microelectromechanical systems for biomimetical application." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7955.

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The application of adaptive micro-electro-mechanical systems (MEMS) device in biologically-inspired cochlear model (cochlear biomodel) has been seen as a preferable approach to mimic closely the human cochlear response. The thesis focuses on the design and fabrication of resonant gate transistor (RGT) device applied towards the development of RGT cochlear biomodel. An array of RGT devices can mimic the cochlea by filtering the sound input signals into multiple electrical outputs. The RGT device consists of two main components; a) the MEMS bridge gate structure that transduces the sound input into mechanical vibrations and b) the channel with source/drain regions underneath the bridge gate structure that transduce the mechanical vibrations into electrical signals. The created mathematical model for RGT calculates the electrical outputs that are suited for neural spike coding. The neuromorphic auditory system is proposed by integrating the RGT devices with the spike event interface circuits. The novelty of the system lies in the adaptive characteristics of the RGT devices that can self-tune the frequency and sensitivity using the feedback control signals from the neuromorphic circuits. The bridge gates have been designed to cover the audible frequency range signals of 20 Hz - 20 kHz. Aluminium and tantalum have been studied as the material for the bridge gate structure. The fabrication of a bridge gate requires a gentle etch release technique to release the structure from a sacrificial layer. The downstream etch release technique employing oxygen/nitrogen plasma has been introduced and characterised. In the first iteration, aluminium bridge gates have been fabricated. The presence of tensile stress within aluminium had caused the aluminium bridge gates of length >1mm to collapse. In order to address this issue, tantalum bridge gates have been fabricated in the second iteration. Straight tantalum bridge gates in tensile stress and buckled tantalum bridge gates in compressive stress have been characterised. The frequency range of 550 Hz - 29.4 kHz has been achieved from the fabricated tantalum bridge gates of length 0.57mm - 5.8mm. The channel and source/drain regions have been fabricated and integrated with the aluminium or tantalum bridge gate structures to create the RGTs. In this study, the n-channel and p-channel resonant gate transistor (n-RGT and p-RGT) have been considered. In n-RGT, phosphorus ions are implanted to form the source/drain regions. High subthreshold currents have been measured from the n-RGTs. Thus, p- RGTs have been employed with considerably small subthreshold current. In p-RGT, boron ions are implanted to form the source/drain regions. The threshold voltage, transconductance and subthreshold current for both n-channel and p-channel resonant gate transistor devices have been characterised. In this work, the channel conductance of the n-RGT and p-RGT devices has been modulated successfully and the sensitivity tuning within the audible frequency range has been achieved from the tantalum bridge gates of the p-RGT devices. The characterisation and optimisation of the resonant gate transistor provide the first step towards the development of the adaptive RGT cochlear biomodel for the neuromorphic auditory system application.

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Gale, Jonathan Edward. "Mechanosensitivity of the basolateral membrane of outer hair cells from the mammalian cochlea." Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240651.

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Breglio, Andrew. "Mechanisms of clinical ototoxicity and inner ear protection." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:2490cfc1-c58c-4844-b838-0491b6db7dd4.

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Clinical ototoxicity - permanent hearing loss caused by medications - is estimated to affect millions of patients annually. Two classes of drug are largely to blame: platinum-based chemotherapeutics, primarily cisplatin, and aminoglycoside antibiotics. Development of methods to prevent ototoxicity depends upon an understanding of its mechanisms and may benefit from an understanding of native protective pathways of the inner ear. As the mechanisms behind cisplatin ototoxicity remain unclear, I first sought, and herein report, a refined mouse model of cisplatin ototoxicity which will allow for further in vivo investigation of cisplatin ototoxicity and potential methods for its prevention. This low-dose, multi-cycle model was found to accurately reproduce cisplatin ototoxicity as it has been described clinically and histopathologically. I then used this mouse model of cisplatin ototoxicity to investigate cisplatin pharmacokinetics in the cochlea and their role in driving cisplatin ototoxicity. Cisplatin was found to be retained within the cochlea for months following its administration. This initial finding in mice was extended to cochlear tissue samples from deceased human patients. Analysis of intra-cochlear cisplatin distribution in murine and human tissue identified the stria vascularis region of the cochlea as a promising target for intervention. With the nature of aminoglycoside ototoxicity better understood, I investigated a native inner ear protective pathway which could be leveraged to promote sensory hair cell survival. The improved hair cell survival that has previously been demonstrated as a result of heat stress was found to be mediated by cell-cell communication via extracellular vesicles. Further, hair cell protection against aminoglycosides could be reproduced through the application of exogenous, non-inner ear-derived extracellular vesicles. In sum, these data provide new insight into mechanisms of ototoxicity and details of cellular pathways which can help protect against it.

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Boatright, Rebecca D. "Mechanisms for gain control and temporal processing in the auditory brainstem of the big brown bat, Eptesicus fuscus /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/9147.

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Lagarde, Marcia Maria Mellado. "A role for prestin in amplification, otoacoustic emissions, and shaping mechanical tuning in the cochlea." Thesis, University of Sussex, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487001.

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28

Hartmann, Julia [Verfasser], and Dominik [Akademischer Betreuer] Oliver. "Analysis of the molecular mechanisms of prestin-mediated cochlear amplification via a cysteine accessibility study / Julia Hartmann ; Betreuer: Dominik Oliver." Marburg : Philipps-Universität Marburg, 2021. http://d-nb.info/1232406031/34.

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Rosengard, Peninah S. 1970. "Relationship between measures related to the cochlear active mechanism and speech reception thresholds in backgrounds with and without spectral and/or temporal fluctuations." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28598.

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Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2004.
Includes bibliographical references (p. 191-203).
The importance of the cochlear active mechanism in the reception of speech in different types of noise was explored. The perceptual effects of loudness recruitment, a consequence of loss of the active mechanism, were assessed in simulated-loss listeners using a multiband expansion algorithm that models abnormal cochlear linearity. While this algorithm, which derives the expansion characteristic from absolute hearing thresholds, can accurately simulate the mean speech intelligibility results of hearing-impaired listeners, its ability to simulate the performance of individual listeners is limited. Given the relationship between loudness perception and the active mechanism, deriving the expansion characteristic from estimates of cochlear compression should provide a more accurate model of an individual listener's impairment. Towards this aim, the reliability of two psychoacoustic methods used to estimate the magnitude of compression (growth of masking and temporal masking) was assessed. Results suggest that growth of masking is a more reliable measure of compression in listeners with both normal and impaired hearing. The relationship between the compressive characteristics of the auditory system and speech perception in complex acoustic backgrounds was also evaluated. The operational status of the active mechanism was assessed behaviorally using three independently derived measures: (1) slope ratio of off- and on-frequency growth of masking functions, (2) equivalent rectangular bandwidth of auditory filters, and (3) masker-phase masking differences. These measures were correlated with speech reception thresholds (SRTs) in backgrounds with and without spectral and/or temporal-modulations. The relationship between slope ratios, filter bandwidths, and the maximum
(cont.) SRT difference (SRT in steady noise minus SRT in temporally modulated, spectral gap noise) was significant. These results indicate that the ability to take advantage of momentary fluctuations in the amplitude or frequency spectrum of background noise requires an intact active mechanism. The speech reception performance of two hearing-impaired listeners was modeled using a customized version of the expansion algorithm. The algorithm was customized to an individual's impairment based on psychoacoustic measures used to evaluate the integrity of the active mechanism. The maximum SRT difference in the simulated-loss listeners more closely matched the results of their hearing-impaired counterparts, compared to SRTs measured using the original algorithm. These results provide further evidence of the importance of the active mechanism to the perception of speech in modulated noise.
by Peninah S. Rosengard.
Ph.D.

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30

Garbes, Peter A. Z. (Peter Angelito Zaragoza). "Evaluating human neural tuning curves from a mechanical model of the cochlea by relating them to psychophysical masking data." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/34073.

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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.
Includes bibliographical references (leaves 40-42).
by Peter A.Z. Garbes.
M.S.

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31

Niu, Xianzhi. "The functional role of the lateral olivocochlear system and mechanisms underlying sound conditioning /." Stockholm, 2004. http://diss.kib.ki.se/2004/91-7140-094-X/.

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32

Jean, Philippe Verfasser], Tobias [Akademischer Betreuer] [Moser, Thomas [Gutachter] Dresbach, and Andreas [Gutachter] Neef. "Dissecting synaptic mechanisms of sound encoding in the mouse cochlea / Philippe Jean ; Gutachter: Thomas Dresbach, Andreas Neef ; Betreuer: Tobias Moser." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://d-nb.info/1186968222/34.

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Jean, Philippe [Verfasser], Tobias [Akademischer Betreuer] Moser, Thomas [Gutachter] Dresbach, and Andreas [Gutachter] Neef. "Dissecting synaptic mechanisms of sound encoding in the mouse cochlea / Philippe Jean ; Gutachter: Thomas Dresbach, Andreas Neef ; Betreuer: Tobias Moser." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://d-nb.info/1186968222/34.

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34

Becker, Sebastian [Verfasser], Herbert [Akademischer Betreuer] Hudde, and Karlheinz [Akademischer Betreuer] Ochs. "A physiology-based circuit model of the human peripheral ear revealing the mechanisms of non-linear active cochlear gain and otoacoustic emissions / Sebastian Becker. Gutachter: Herbert Hudde ; Karlheinz Ochs." Bochum : Ruhr-Universität Bochum, 2016. http://d-nb.info/1095884980/34.

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35

Bowman, Denise Michelle. "Estimating mechanical frequency tuning properties of the cochlea with f¦1- and f¦2-sweep distortion-product otoacoustic emission measurements in normal hearing human adults." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0001/NQ34658.pdf.

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36

Watts, Donald Lloyd. "Cochlear Mechanics: Analysis and Analog VLSI." Thesis, 1993. https://thesis.library.caltech.edu/2802/1/LloydWattsthesis.pdf.

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The cochlea separates sounds based on their frequency content and on their fine time structure, using an active and nonlinear fluid-mechanical traveling-wave mechanism. This dissertation describes a simplified model of the cochlear mechanics problem, and techniques for solving the problem.

The Liouville-Green (LG) method has been used to obtain analytical solutions for the cochlear mechanics problem; however, the failure of the method to agree quantitatively with numerical methods has left doubts about its validity. In this dissertation, it is shown that the LG method fails to solve the problem, and that an additional degree of freedom is required for a consistent solution. The additional degree of freedom corresponds to a second wave mode, which has been observed experimentally in the cochleas of living animals. The new mode-coupling LG solution agrees quantitatively with numerical solutions. This problem has been outstanding since 1971.

In addition to analytical techniques, this dissertation also presents analog circuit techniques, specifically for the medium of analog very-large-scale-integration (VLSI) complementary metal-oxide-semiconductor (CMOS) technology. A silicon cochlea that models the behavior of the passive cochlea has been fabricated and tested. The silicon cochlea operates in real time with 8 mW of power dissipation.

The active and nonlinear behavior of the cochlea is a subject of intense research interest at the present time, and many issues are still unresolved. A preliminary model of active elements in the cochlea is described and characterized, and shown to be consistent with the prevailing views of active cochlear function.

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37

Lin, Nathan Ching. "Fiber-optic probe and bulk-optics Spectral Domain Optical Coherence tomography systems for in vivo cochlear mechanics measurements." Thesis, 2019. https://doi.org/10.7916/d8-xmhj-ap89.

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Acquiring the motions of the inner ear sensory tissues provides insight to how the cochlea works. For this purpose, Spectral Domain Optical Coherence Tomography (SDOCT) is an ideal tool as it has a penetration depth of several millimeters. SDOCT can not only image inside the cochlear partition, but also measure the sample structures’ simultaneous displacements. We customized a commercial Spectral Domain Optical Coherence Tomography system for such functions and detailed the software and hardware steps so this powerful system could be more accessible to auditory researchers. The cochlea is surrounded by bones and tissues, and damage to it would make it passive. For this reason, cochlear vibrometry measuring locations have been limited to either the basal or apical regions. That is why I fabricated a two-dimensional scanning SDOCT-based probe, to access more cochlear locations through a small hand-drilled hole. What is exciting about the probe is that an electrode can be attached to its side to acquire spatially and temporally coincident voltage and displacement data. This would help us better understand the cochlear mechano-electrical feedback process. Lastly, I investigated how the SDPM-reported displacement could be influenced by its neighboring signals and demonstrated this signal competition phenomenon experimentally and theoretically.

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Lin, Chia-Der, and 林嘉德. "The cellular mechanisms and therapeutic implications of cochlear ischemia." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/60916557497126534820.

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博士
中國醫藥大學
臨床醫學研究所博士班
99
The cochlea is a highly metabolic organ and requires much energy to maintain the normal physiologic function. However, it is an end-artery organ and mainly supplied by the labyrinthine artery, which is a branch of anterior inferior cerebellar artery (AICA). Therefore, the cochlea is sensitive to disturbance of blood flow. Cochlear ischemia has been implicated to be the causative factor in various hearing disorders such as noise induced hearing loss, presbyacusis, or sudden deafness. The first aim of this thesis is to establish an animal model of reversible cochlear ischemia after the detailed exploration of the inner ear circulation. The interaction of aminoglycoside ototoxicity and bioenergetic deficiency of cochlea is then explored. In addition, the in vivo model in coordination with in vitro cochlear ischemia model will provide a new approach to the investigation of the cellular and molecular mechanisms in cochlear ischemia. In this thesis, the detailed exploration of the inner ear circulation in guinea pigs was completed, followed by the establishment of a reversible cochlear ischemia model in guinea pigs (chapter 2). The time courses and dose responses of cochlear ischemia in guinea pigs were shown in chapter 3. The effects of hyperbaric oxygen on guinea pig cochlea were investigated and demonstrated in chapter 4, which could provide the basis for future researches in therapeutic applications. This thesis also established an animal model of acute cochlear mitochondrial dysfunction to elucidate the interaction of aminoglycoside ototoxicity with bioenergetic deficiency (chapter 5). Increased aminoglycoside ototoxic susceptibility was depicted in the impaired bioenergetic deficiency of acute cochlear mitochondrial dysfunction and ischemia-reperfusion injuries. The molecular mechanisms after the interaction of aminoglycoside and hypoxia/ischemia was investigated via the in vitro model using HEI-OC1 cochlear cell line and described in chapter 6. Finally, previous researches on the therapeutic purposes for cochlear ischemic damage were reviewed in chapter 7. The potential therapeutic opportunities for the ischemia-related hearing losses were raised. By virtue of the in vitro and in vivo model, some evidence-based therapeutic strategies may be identified, which may be useful in clinical applications.

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39

Jean, Philippe. "Dissecting synaptic mechanisms of sound encoding in the mouse cochlea." Doctoral thesis, 2019. http://hdl.handle.net/11858/00-1735-0000-002E-E645-8.

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Lin, Yu-Chieh, and 林郁傑. "Application of gammachirp filter banks to simulate the auditory cochlea mechanism of hearing impaired people." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/58656920512775251879.

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碩士
國立臺灣大學
工程科學及海洋工程學研究所
95
As far as hearing-impaired people is considered, they might encounter the difficulties in the process of learning and communication due to not able to perceive the complete signal of sounds in the correct way, which leads normal people have misunderstanding and wrong perception towards hearing-impaired people. If normal people without hearing problems can sense or really hear the voices or sounds which hearing-impaired people actually receive by means of certain instrument or tool, we can truly understand and realize such inconveniences of life and learning process for hearing-impaired people; moreover we can assist to improve their lives by solving the problems caused by hearing impairment. The cochlea plays a very important and critical role of analysis of signal of sounds in entire hearing system. Since the basilar membrane inside cochlea reacts different responses on amplitudes and frequency of the signal of sounds, its function works as one band pass filter bank. The high frequency of sound causes bigger response to the base of cochlea; on the contrary, the low frequency of sound results in bigger response to the apex of cochlea. The research objective is to explore that each point of the basilar membrane inside cochlea has its property of the band pass filter bank while shows in the frequency responses to voice wave, since each point has its characteristic frequency. In accordance of the principle of digital band pass filter bank, we specifically design the parallel connection of band pass filter bank, and the band pass filter bank respectively utilize one-third-octave and critical band as the method to divide the band, which is to simulate the selectivity of the cochlea towards the frequency intensity. In another hand, the filter bank of gammatone and of gammachirp, published and designed by the cochlea measurement experiment consistent of physical and psychological auditory mechanism, will be used to simulate the auditory cochlea mechanism of the inner cochlea. Then, the outer ear, middle ear will be connected with the filter bank of gammatone and of gammachirp by the way of cascade connection to simulate the peripheral auditory system and mechanism of outer ear, middle ear and inner ear altogether. In this research, four different types of filter banks will be designed to test the signal of sounds, which can verify and prove whether these filter banks can really function and be consistent of the properties of frequency selectivity of the cochlea. Accordingly we can design different hearing loss filter banks in accordance with the different level of hearing loss. When the signal of sounds passes through filter banks, we can simulate and imitate the signal of sounds which hearing impaired people actually receive. Through such a devise, the normal people can actually hear this type of sounds; they can really understand when they put themselves in people’s shoes. We hope that we can really understand and realize their difficulties and inconveniences which they have to face everyday by this experience; then we can further assist them and help them to improve their lives and make their lives better and easier.

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Yang, Zhen-Yu, and 楊鎮宇. "Application of Quadrature Mirror Filter Banks to simulate the auditory cochlea mechanism of hearing impaired people." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/44194457922718759267.

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碩士
國立臺灣大學
工程科學及海洋工程學研究所
97
Being incapable of perceiving the complete voice contain will lead to hearing impaired people to have learning difficulty on language acquisition.Moreover, normal people without hearing problems may subjectively comprehend the reactions of impaired listeners during communication. Hence, it is difficult for normal people to tackle the core of problems and assist the hearing impaired to overcome communication barriers. We simulate the voice that hearing impaired people might receive by modulating the sampling frequency with use of shifting devices in this study. It could change the sampling frequency using the sampling frequency shifting devices in order to save the computation workload and time when stimulating. Using Analysis Filter Banks of Quadrature Mirror Filter Banks, we divide the voice into several parts of frequency band, or so called subbands. Next, we multiply them with hearing loss gain. Base on the form of hearing incapability and corresponding bandwidth, and then combine several voice signals subbands with Synthesis Filter Banks of Quadrature Mirror Filter Banks to form one united output signal. In this study, tree-structured Quadrature Mirror Filter Banks and Cosine Modulated Filter Banks are applied to divide natural sound into 32 frequency band of equal same bandwidth. Our work is to stimulate four types of hearing loss, which are 40dB uniform hearing loss, mild low-frequency hearing loss, moderate high-frequency hearing loss, and severe high-frequency hearing loss. Since the signal is nonlinearly producing, combination of several subbands of uniform filter banks is capable of produce non-uniform filter banks with 1/3 one-third-octave approximation. Using three approaches above, we stimulate what is actually perceived by the impaired listeners. Our intention is to imitate the hearing impairment model, and let the public, especially special educators, understand the reactions that hearing impaired individuals make when speaking. More effectively, we can assist them to overcome obstacles in language development when in study. Therefore, man with the loss of hearing is not restricted or isolated from his or her daily lives and normal social activity.

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Sun, Chi-Chieh, and 孫志杰. "Application of Digital Filter Banks to Implement the Auditory Cochlea Mechanism of Hearing Impaired People on the DSP." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/52754764700764911027.

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Perlácová, Tereza. "Počítačové modelování vnitřního ucha." Master's thesis, 2017. http://www.nusl.cz/ntk/nusl-367585.

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Do mechanického modelu kochley zavádzame implicitné numerické metódy. Tes- tujeme konkrétne štyri metódy: implicitný Euler, Crank-Nicolson, BDF druhého a tretieho rádu na lineárnej a nelineárnej verzii modelu. Nelineárny model obsahuje funkciu so saturujúcou vlastnosťou. Aplikácia implicitných metód na nelineárny model vedie na sústavu nelineárnych rovníc. Predstavujeme dva spôsoby, ako túto sústavu numericky riešiť. Prvý z nich zahrňuje nelinearitu do pravej strany novovzniknutej lineárnej sústavy. Druhý robí linearizáciu nelineárnej funkcie. V práci porovnávame oba spôsoby z hľadiska efektivity a sledujeme ich konvergenciu k referenčnému riešeniu. Pre hodnotu tolerancie, ktorú používame na určenie numerickej konvergencie, je prvý spôsob efektívnejší. V úplne nelineárnom režime druhý spôsob zlyháva, pretože nekon- verguje k referenčnému riešeniu. Výsledkom porovnania implicitných metód je, že Crank-Nicolsonova metóda s prvým spôsobom riešenia nelineárnej sústavy je pre účely nášho modelu najlepšia. Použitie tejto metódy v mechanickom modeli nám umožňuje vytvoriť ľubovoľne presné prepojenie medzi mechanickým a elektrickým modelom kochley, rešpektujúc fyziológiu človeka. 1

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Chen, Jia-Xian, and 陳佳賢. "Application of Active Gammachirp Filter Banks to Simulate the Auditory Cochlea Mechanism of Hearing Impaired People on the DSP Chip." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/78771382948100842101.

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碩士
國立臺灣大學
工程科學及海洋工程學研究所
97
It is not a few hearing-impaired people globally and everyone pays greater attention to the subject gradually. There were Chinese National Association of the Deaf and hearing-impaired foundations to help the hearing-impaired people in the earlier days, and now a days the Deaf Olympic shows that the importance of hearing-impaired subject. As regards to the hearing-impaired people, due to being unable to perceive the complete voice signals, they might encounter many difficulties in learning and communication and drive regular people to get misunderstood. Accordingly, supposed a regular people can feel or really hear the voices which hearing-impaired people actually receive through some special instruments or tools, they can really experience some inconvenient problems of learing in life to know the difference between a regular and a hearing-impaired people. Thus mistakes are reduced to get help on improving the problems resulting from hearing-impaired. Because the cochlea is the most important one of auditory system, this thesis is to design cochlea auditory filter banks by using the principle of digital filter banks to apply on the simulation of the voices actually received by the hearing-impaired people combining with digital signal processor TMS320C6713 DSK produced by Ti. We can first understand the feature of the cochlea by surveying the papers published in some journals involved, then use the gammatone filter bank and active gammachirp filter bank to simulate the different degree of hearing-impaired hearing loss of cochlear mechanisms. Finally we use the Matlab and DSP processor to approve and implement the sense of hearing of hearing-impaired people in real-time and convenient situations. Therefore, the fact as talked can make those people of normal hearing feel the sense of hearing-impaired people and also understand much more what the hearing-impaired people really need.

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(11189856), Vibha Viswanathan. "Neurophysiological Mechanisms of Speech Intelligibility under Masking and Distortion." Thesis, 2021.

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Difficulty understanding speech in background noise is the most common hearing complaint. Elucidating the neurophysiological mechanisms underlying speech intelligibility in everyday environments with multiple sound sources and distortions is hence important for any technology that aims to improve real-world listening. Using a combination of behavioral, electroencephalography (EEG), and computational modeling experiments, this dissertation provides insight into how the brain analyzes such complex scenes, and what roles different acoustic cues play in facilitating this process and in conveying phonetic content. Experiment #1 showed that brain oscillations selectively track the temporal envelopes (i.e., modulations) of attended speech in a mixture of competing talkers, and that the strength and pattern of this attention effect differs between individuals. Experiment #2 showed that the fidelity of neural tracking of attended-speech envelopes is strongly shaped by the modulations in interfering sounds as well as the temporal fine structure (TFS) conveyed by the cochlea, and predicts speech intelligibility in diverse listening environments. Results from Experiments #1 and #2 support the theory that temporal coherence of sound elements across envelopes and/or TFS shapes scene analysis and speech intelligibility. Experiment #3 tested this theory further by measuring and computationally modeling consonant categorization behavior in a range of background noises and distortions. We found that a physiologically plausible model that incorporated temporal-coherence effects predicted consonant confusions better than conventional speech-intelligibility models, providing independent evidence that temporal coherence influences scene analysis. Finally, results from Experiment #3 also showed that TFS is used to extract speech content (voicing) for consonant categorization even when intact envelope cues are available. Together, the novel insights provided by our results can guide future models of speech intelligibility and scene analysis, clinical diagnostics, improved assistive listening devices, and other audio technologies.

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Chapochnikov, Nikolai. "Modeling the biophysical mechanisms of sound encoding at inner hair cell ribbon synapses." Doctoral thesis, 2011. http://hdl.handle.net/11858/00-1735-0000-000D-F092-3.

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Dissertations / Theses on the topic 'Cochlear mechanics'

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