Mechanics of Hearing: Proceedings of the IUTAM/ICA Symposium held at Delft University of Technology The Netherlands 13–15 July 1983 PDF
Preview Mechanics of Hearing: Proceedings of the IUTAM/ICA Symposium held at Delft University of Technology The Netherlands 13–15 July 1983
MECHANICS OF HEARING MECHANICS OF HEARING PROCEEDINGS of the IUTAM/ICA SYMPOSIUM held at Delft University of Technology The Netherlands 13-15 July 1983 Edited by E. de Boer and M.A. Viergever 1983 MARTINUS NIJHOFF PUBLISHERS a member of the KLUWER ACADEMIC PUBUSHERS GROUP THE HAGUE / BOSTON / LANCASTER and DELFT UNIVERSITY PRESS DELFT Distributors for the United States and Canada: Kluwer Boston, Inc. 190 Old Derby Street Hingham, MA 02043 USA for all other countries: Kluwer Academic Publishers Group Distribution Centre P.O. Box 322 3300 AH Dordrecht The Netherlands Cover Front cover shows a painting, entitled 'Auricles', 1982, by Inez Merhottein, Voorburg, The Netherlands. Book information Joint edition published by: Martinus Nijhoff Publishers, The Hague, The Netherlands and Delft University Press, Delft, The Netherlands ISBN-13: 978-94-009-6913-1 e-ISBN-13: 978-94-009-6911-7 DOl: 10.1007/978-94-009-6911-7 Copyright © by Delft University Press, The Netherlands. Softcover reprint of the hardcover 1s t edition 1983 All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, mechanical, photocopying, recording or otherwise, without written permission of Delft University Press, Mijnbouwplein 11, 2628 RT Delft, The Netherlands. PROSPERa - Dost thou hear? MIRANDA - Your tale, Sir, would cure deafness. Shakespeare, The Tempest, Act 1, Sc. 2. VII CONTENTS Welcome to the readers IX Section I: EXTERNAL EAR AND MIDDLE EAR Shaw, E.A.G., Stinson, M.R. The human external and middle ear: 3 Models and eoneepts. Matthews, J.W. Modeling reverse middle ear transmission of aeoustie 11 distortion signals. Funnell, W.R.J. Reeent developments in modelling the eardrum and 19 related struetures using the finite-element method. Section II: COCHLEAR FLUID MECHANICS Steele, C.R., Zais, J. Basilar membrane properties and eoehlear 29 response. Babic, V.M., Novoselova, S.M. On vibration of membranes in the 37 mammalian eoehlea. Holmes, M., Cole, J.D. Pseudo-resonanee in the eoehlea. 45 Viergever, M.A., Diependaal, R.J. Simultaneous amplitude and phase 53 mateh of eoehlear model ealeulations and basilar membrane vibration data. Lighthill, J. Advantages from deseribing eoehlear meehanies in terms 63 of energy flow. Section III: COCHLEAR EMISSIONS Kemp, D.T., Brown, A.M. An integrated view of eoehlear meehanieal 75 nonlinearities observable from the ear eanal. Sutton, G.J., Wilson, J.P. Modelling eoehlear eehoes: The influenee 83 of irregularities in frequeney mapping on summed eoehlear aetivity. Rutten, W.L.C., Buisman, H.P. Critieal behaviour of auditory oseil- 91 lators near feedbaek phase transitions. Wit, H.P.,Ritsma, R.J. Two aspects of eoehlear acoustie emissions: 101 Response latency and minimum stimulus energy. Section IV: ACTIVE SYSTEMS Neely, S.T. The eochlear amplifier. 111 Mountain, D.C., Hubbard, A.E., McMullen, T.A. Eleetromeehanieal 119 processes in the eoehlea. Koshigoe, S., Tubis, A. A non-linear feedbaek model for outer-hair- 127 cell stereoeilia and its implications for the response of the auditory periphery. VIII Boer, E. de. Wave reflection in passive and active cochlea models. 135 Netten, S.M. van, Duifhuis, H. Modelling an active, nonlinear 143 cochlea. Diependaal, R.J., Viergever, M.A. Nonlinear and active modelling 153 of cochlear mechanics: A precarious affair. Section V: NONLINEAR MICROMECHANICS Voldrich, L. Experimental and topographic morphology in cochlear 163 mechanics. Jau, Y.C., Geisler, C.D. Results from a cochlear model utilizing 169 longitudinal coupling. Khanna, S.M., Leonard, D.G.B. An interpretation of the sharp tuning 177 of the basilar membrane mechanical response. Section VI: SPECIAL TOPICS Bialek, W. Thermal and quantum noise in the inner ear. 185 Allen, J.B. A hair cell model of neural response. 193 Miller, C.E. Static point-load measurements of basilar membrane 203 compliance. Kohl16ffel, L.U.E. Problems in aural sound conduction. 211 IX Welcome to the readers This book gives an account of present-day attempts at solving the problems posed by the truly amazing capabilities or our hearing organs. The emphasis is on those aspects of the external ear, the middle ear and the cochlea which, to the best of our present knowledge, can be treated by a mechanistic analy- sis. The book represents the proceedings of a Symposium on Mechanics of Hea- ring, held at Delft (the Netherlands) in July 1983. The symposium was jointly sponsored by the International Union of Theoretical and Applied Mechanics (IUTAM) and the International Commission on Acoustics (ICA) and it functioned as a special symposium associated with the 11th ~nternational Congress on Acoustics in Paris. A scientific committee was appointed (see list below) under the chairmanship of the undersigned. The committee selected a number of possible contributors, and requested suggestions for additional contributors. In this way the core of the symposium programme was constructed. Each author had to produce a camera-ready manuscript which means that the authors are fully responsible for their texts. In a few instances the Bureau of the Symposium provided help to the authors to ensure that all manuscripts were typed according to the same rules. The book was made available at the time of the Symposium thanks to the diligence of Delft University Press. The following gives a guide as to the contents of the book. The first topic is called: 'External ear and middle ear'. A review paper by Shaw and Stinson analyzes the many physical properties that have been demonstrated in these organs. Sound is affected by structures of complex geometry. A modern way of attacking the problem of complexity is demonstrated by Funnell in his contri- bution on vibrations of the drum membrane. Sound does not only go from 'air' to 'ear' but - in view of cochlear emissions and other active, nonlinear phe- nomena - also in the opposite direction. See the paper by Matthews on the transmission of sound generated in the inner ear back to the middle ear and to the external ear. x The second main section of the book concerns 'Cochlear fluid mechanics', this subject more or less represents the 'classical' approach in cochlear mechanics. The section brings together a number of papers, mostly of a fundamental na- ture, treating the problem as to how cochlear fluids interact with cochlear membranes. One of the most versatile solution methods, the LG (Liouville- Green) or WKB (Wentzel, Kramers and Brillouin) method, is applied by Steele and Zais to cochlear structures of fairly complex geometry. Other applica- tions of that method in two- and three-channel cochlear models, are presen- ted by Babi~ and Novoselova. A different approach, more easily recognized as an asymptotic method, is illustrated by Holmes and Cole. To what extent expe- rimental data can be explained in terms of 'classical' models is demonstra- ted by Viergever and Diependaal. Very fundamental properties of models incorporating 'short waves' and the ways these properties are interconnected form the topic of the paper by Lighthill. With the advent of 'Cochlear emissions' - the name of the next section - a new era seemed to start in the field of hearing theory. New experimental findings and a novel interpretation are presented in Kemp's contribution to this book. It is difficult to grasp all data and to construct a comprehen- sive model to explain them all, hence the studies of simplified models. See, for instance, the paper by Sutton and Wilson. More experimental data are pre- sented by Rutten and Buisman. These authors also relate the emission phenome- na to subjects of study in completely different fields of research: phase transitions of oscillators that operate near their critical points. One bridge too far? Certainly not! Finally, Wit and Ritsma consider spontaneous emissions in frequency and time. They also try to determine the minimal sti- mulus level that gives rise to an evoked emission - with a surprising result. The fourth main topic, obviously related to the previous one, is 'Active Systems'. Several authors in this field claim that the classical, passive cochlea model is not capable of explaining the essential elements of the most recent findings regarding vibrations in the cochlea. When a model is assumed to be active, i.e., to have the property that cochlear structures can actively generate acoustic energy, it is feasible to obtain a well- fitting response. This is demonstrated by the model responses obtained by Neely. Mountain, Hubbard and McMullen describe more general aspects of an active model and the way computed responses relate to experimental evidence, whereas Koshigoe and Tubis concentrate on feedback properties of an active model. XI In both papers nonlinearity appears as an essential feature of the model. Problems associated with reflections of waves generated inside the cochlea by active behaviour are analyzed by de Boer. Van Netten and Duifhuis give an account of their first attempt at an analytical approach: the dynamics of the organ of Corti is described by the Van der Pol equation. Diependaal and Viergever studied numerical techniques for solving the problem of an active structure. They find one of the most advanced methods to fall definitely short of the goal in active models and they elucidate the reason for this property. The fifth section of the book, entitled 'Nonlinear micromechanics', tries to delve somewhat deeper into the problem of how the specific properties of the organ of Corti are brought about. Voldrich presents an account of the most recent anatomical findings. Jau and Geisler consider nonlinear effects as dependent upon a weighted average of basilar membrane displacement over a certain length. Khanna and Leonard enumerate the arguments why they think tuning properties of the cilia of cochlear hair cells are crucial, a feature that has been keeping theorists busy for a long time. A number of 'Special topics' remain, difficult to be brought under one hea- ding. Miller's experimental results on the static compliance of the basilar membrane contribute to present-day discussion on this topic. Allen shows how the dynamics of neural excitation in hair cells can be taken into account. Questions of sound conduction in water birds, the role of the cochlear aqua- duct and the significance of a flexible spiral lamina are considered by Kohl- loeffel. Bialek, finally, approaches the problem of cochlear action from quite a different angle. He calculates the noise level resulting from Brownian motion and finds this to be at least 20 - 30 dB above our hearing threshold. According to these results there should exist a filtering process subsequent to cochlear mechanics. Many thanks are due to the sponsoring agencies: IUTAM and ICA. The coopera- tion with the Department of Mathematics and Informatics, Delft University of Technology, served well to make the meeting a success. The undersigned gratefully acknowledges the work done by the scientific committee (see list below). The many contributions from Dr. M.A. Viergever who assumed the labo- rious task of Secretary of the Symposium, deserve to be mentioned specifi- cally. XII The same applies to Mrs. M. den Boef who undertook the greater part of the local organization and administration work. Let us all hope that the present book will be a milestone along the road of modelling of the auditory system. E. de Boer chairman The scientific Committee: Sir James Lighthill, London, UK C.R. Steele, Stanford, CA, USA E.A.G. Shaw, Ottawa, Canada E. de Boer, Amsterdam, Neth. (chairman) M.A. Viergever, Delft, Neth. (secretary)
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