Middle Ear Pressure Gain and Cochlear Input Impedance in the Chinchilla


Book Description

Measurements of middle ear conducted sound pressure in the cochlear vestibule PV have been performed in only a few individuals from a few mammalian species. Simultaneous measurements of sound-induced stapes velocity VS are even more rare. We report simultaneous measurements of VS and PV in chinchillas. The VS measurements were performed using single-beam laser-Doppler vibrometry; PV was measured with fiber optic pressure sensors like those described by Olson [JASA 1998; 103: 3445-63]. Accurate in-vivo measurements of PV are limited by anatomical access to the vestibule, the relative sizes of the sensor and vestibule, and damage to the cochlea when inserting the measurement device. The small size (170 [mu]m diameter) of the fiber-optic pressure sensors helps overcome these three constraints. PV and VS were measured in six animals, and the middle ear pressure gain (ratio of PV to the sound pressure in the ear canal) and the cochlear input impedance (ratio of PV to the product of VS and area of the footplate) computed. Our measurements of middle ear pressure gain are similar to published data in the chinchilla at stimulus frequencies of 500 Hz to 3 kHz, but are different at other frequencies. Our measurements of cochlear input impedance differ somewhat from previous estimates in the chinchilla and show a resistive input impedance up to at least 10 kHz. To our knowledge, these are the first direct measurements of this impedance in the chinchilla. The acoustic power entering the cochlea was computed based on our measurements of input impedance. This quantity was a good predictor for the audiogram at frequencies below 1 kHz.




Concepts and Challenges in the Biophysics of Hearing


Book Description

This book is a compilation of cutting-edge research on the mechanical operation of the peripheral auditory system. Bringing together over 50 theoretical and experimental studies by leading researchers, it covers the molecular, cellular and systems levels using a powerful combination of biological, mathematical and engineering techniques. In addition to the scientific papers, the book includes the comments and discussions raised by the individual manuscripts at the time of their presentation, and a final chapter with the edited transcripts of a discussion session covering "outstanding topics" between some of the most prominent researchers in the field. The first-hand information provided by these transcripts will make the book particularly interesting.Renowned contributors to the book include Profs. JF Ashmore (FRS, UK), E de Boer (The Netherlands), W Brownell (USA), P Dallos (USA), R Fettiplace (FRS, USA), AW Gummer (Germany), AJ Hudspeth (USA), DC Mountain (USA), AL Nuttall (USA), IJ Russell (FRS, UK), CA Shera (USA), and H Wada (Japan).




Role of Middle-ear Inertial Component of Bone Conduction in Chinchilla


Book Description

Bone conduction describes the mechanisms that produce a hearing sensation when the skull bones are subjected to vibration. Multiple components and pathways have been suggested to contribute to total bone-conducted sound. They include outer-ear cartilaginous wall compression, middle-ear inertia, fluid inertia, cochlear capsule compression and soft-tissue conduction. Due to the complexity of the possible interactions within these components and pathways, the true stimulus to the inner ear is not fully understood nor has it been adequately quantified. In this thesis work, we examined the relationship between inner-ear sound pressures and its sensory response in addition to determining the relative significance between the outer, middle and inner ear mechanisms that are prominent in bone conduction hearing in chinchilla. Using both mechanical and physiological recording techniques, we measured cochlear responses in chinchilla before and after interruption of the middle-ear ossicular system in both air conduction (AC) and bone conduction (BC) stimulation. Our data suggest that differential intracochlear sound pressure is the driving source to the sensory response of the inner ear in AC and BC. Compared to those in AC, inner-ear sound pressure measurements in BC provide evidence of multiple mechanisms in BC process. After middle ear interruption, pressures in scala vestibuli Psv and scala tympani PST drop by as much as 40 dB in AC, but only decrease in Psv by 10 dB, with almost no change in PST in BC. The difference in the change of both Psv and PST in BC compared to AC suggest the main mechanisms that drive the inner ear response in BC are not derived from the outer ear or middle ear but the inner ear.




Biophysics of the Cochlea


Book Description

This book contains the proceedings of an intenational hearing-research conference held in Germany 2002. The conference brought together experts in genetics, molecular and cellular biology, physiology, engineering, physics, mathematics, audiology and medicine to synthesize and extend our understanding of how the cochlea works. Topics are discussed experimentally and theoretically at the molecular, cellular and whole-organ levels. Some of the topics are: mechanosensitivity of motor proteins; mechanochemical transduction by motor proteins; mechanoelectrical transduction in the stereocilia of hair cells; electromechanical transduction in the stereocilia, soma and synapses of hair cells; multidimensional vibration of the organ of Corti; and otoacoustic emissions. This book will be invaluable to researchers and students in auditory science. Contents: Stereocilia; Hair Cells; Whole-Organ Mechanics; Cochlear Models; Emissions; Comments and Discussions. Readership: Hearing scientists (including medical persons in otolaryngology), biophysicists and molecular' biologists, engineers interested in manufacturing silicon devices (MEMS), and persons interested in modelling biological systems.




Evidence of Inner-ear Mechanisms in Bone Conduction in Chinchillas


Book Description

While much is known about the process of how airborne sound is conducted to the inner-ear via the outer ear and middle ear, so-called air conduction (AC), the mechanisms by which vibrations of the head and body, so-called bone conduction (BC), produce an auditory response are not well understood. It is clear that the inner ear is the sensory site of auditory stimulation by bone conduction, and that the resultant activation of the inner ear has many features in common with air-conduction stimulation; however, bone conduction is known to stimulate the inner ear through multiple pathways. The relative significance and frequency dependence of these different pathways have not been well defined. Our previous work on bone conduction in chinchillas suggested inner-ear mechanisms are the dominant sources in BC. This thesis builds upon the early work by investigating inner ear mechanisms with stapes fixation and ear canal occlusion. Results of stapes fixation show a decrease in scala vestibuli sound pressure Psv and little change in scala tympani sound pressure PST in bone conduction. Ear canal occlusion produces an increase in ear canal sound pressure PEC with a similar amount of increase in Psv, but almost no change in Pst. We attributed the differences in the change between Psv and PST in bone conduction after these manipulations to the existence of compressible cochlear structures or third window pathways, e.g. the cochlear aqueduct. While ear canal compression and middle ear inertia sources may contribute to the total bone conduction response (a 10 dB decrease in Psv after middle ear interruption and stapes fixation, and a 10 dB increase after ear canal occlusion), inner ear mechanisms are still the most significant sources in bone conduction because the changes in Psv and Pst in BC are much smaller than the changes in AC.




Issues in Acoustic and Ultrasound Technology: 2011 Edition


Book Description

Issues in Acoustic and Ultrasound Technology: 2011 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about Acoustic and Ultrasound Technology. The editors have built Issues in Acoustic and Ultrasound Technology: 2011 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Acoustic and Ultrasound Technology in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in Acoustic and Ultrasound Technology: 2011 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.




Issues in Acoustic and Ultrasound Technology: 2012 Edition


Book Description

Issues in Acoustic and Ultrasound Technology: 2012 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about Ultrasound Technology. The editors have built Issues in Acoustic and Ultrasound Technology: 2012 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Ultrasound Technology in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in Acoustic and Ultrasound Technology: 2012 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.







Comparative Hearing: Mammals


Book Description

The Springer Handbook of Auditory Research presents a series of comprehen sive and synthetic reviews of the fundamental topics in modern auditory research. The volumes are aimed at all individuals with interests in hearing research including advanced graduate students, postdoctoral researchers, and clinical investigators. The volumes are intended to introduce new investi gators to important aspects of hearing science and to help established inves tigators to better understand the fundamental theories and data in fields of hearing that they may not normally follow closely. Each volume is intended to present a particular topic comprehensively, and each chapter will serve as a synthetic overview and guide to the lit erature. As such, the chapters present neither exhaustive data reviews nor original research that has not yet appeared in peer-reviewed journals. The volumes focus on topics that have developed a solid data and conceptual foundation rather than on those for which a literature is only beginning to develop. New research areas will be covered on a timely basis in the series as they begin to mature. Each volume in the series consists of five to eight substantial chapters on a particular topic. In some cases, the topics will be ones of traditional interest for which there is a substantial body of data and theory, such as auditory neuroanatomy (Vol. 1) and neurophysiology (Vol. 2). Other volumes in the series will deal with topics which have begun to mature more recently, such as development, plasticity, and computational models of neural processing.




Psychoacoustics


Book Description

Psychoacoustics: Auditory Perception of Listeners with Normal Hearing and Hearing Loss, Second Edition provides an overview of the field of psychoacoustics, with a primary focus on auditory perception. The book retains its focus on applications of psychoacoustics to clinical audiology, and its modular organization, with each chapter including relevant information around a specific topic. Within each chapter, acoustics, physiology, and perception by adult listeners with normal hearing and those with hearing loss, as they relate to that topic, are presented. The influence of hearing loss on these general auditory abilities is discussed in every chapter. Components of the book also include the role of psychoacoustics in audiological assessment and treatment. The text is ideal for audiology students who intend on having a clinical career and need an understanding of both normal and impaired auditory perception. It is intended to give students sufficient information to understand how the ear achieves auditory perception, what the capabilities of the ear are, and how hearing loss influences that perception. It also provides students with a foundation for further study in the area and to apply psychoacoustic principles to diagnostic audiology and audiological rehabilitation. New to the Second Edition: * 70 new figures to clarify some points and facilitate students’ understanding of the material * New chapter that focuses exclusively on the perception by individuals wearing hearing aids and cochlear implants * New section on the perceptual consequences of sensorineural hearing loss on everyday listening added to each chapter * Revamped chapter on Psychoacoustics and Advanced Clinical Auditory Assessment now solely addresses elements within diagnostic audiology that are based on psychoacoustics, with added content on tinnitus assessment, automated (Békésy) audiometry, retrocochlear and pseudohypacusis evaluation, and the identification of dead regions * Enhanced focus on inclusivity, such as alternative versions of some demonstrations designed to be more accessible to individuals with hearing loss, and a new section on the contributions of women and BIPOC scientists to the field of psychoacoustics Key Features: * Learning objectives and summaries begin and end each chapter to convey the goals of the text and review student comprehension * Each chapter contains exercises designed to develop critical thinking about psychoacoustics * Chapters include the following: introduction, relevant acoustics, important physiological studies, perception by normal-hearing listeners, and perception by listeners who have sensorineural hearing loss * Emphasis on applied learning for more effective and efficient learning of the material Disclaimer: Please note that ancillary content such as lab exercises are not included as published in the original print version of this book.