Table Of ContentHEARING SCIENCE
and HEARING DISORDERS
Edited by
M.E. LUTMAN
M.P. HAGGARD
MRC Institute of Hearing Research
University of Nottingham
Nottingham, UK
1983
ACADEMIC PRESS
A Subsidiary ofHarcourt Brace Jovanovich, Publishers
London New York
Paris San Diego San Francisco Säo Paulo
Sydney Tokyo Toronto
ACADEMIC PRESS INC. (LONDON) LTD.
24/28 Oval Road
London NW1
United States Edition published by
ACADEMIC PRESS INC.
Ill Fifth Avenue
New York, New York 10003
Copyright ©1983 by
ACADEMIC PRESS INC. (LONDON) LTD.
All Rights Reserved
No part of this book may be reproduced in any form by photostat, microfilm, or any other
means, without written permission from the publishers
British Library Cataloguing in Publication Data
Hearing Science and Hearing Disorders.
1. Hearing disorders
I. Lutman, M.E.
Π. Haggard, M.P.
617.8 RF290
ISBN 0-12-460440-4
Printed in Great Britain by
Whistable Litho Ltd., Whitstable, Kent
Preface
A main objective of this book is to make
accessible the accelerating fundamental discoveries
of the past decade about the nature of the processes
in the inner ear and the nervous system that mediate
hearing. Many of the details are yet to be filled in
and not all the implications of some of these
findings have yet been fully assimilated. However a
sufficient number of the assumptions and principles
are generally enough accepted to make the moment
right for presenting their implications to a wider
audience, in particular one concerned with hearing
disorders. For example, Evans1 chapter links
advances in auditory physiology to applications in
hearing impairment. More generally, the book as a
whole makes the point that a rigorously established
body of knowledge on hearing impairment and
perceptual processes relevant to disability and to
rehabilitation of the hearing-impaired is
increasingly available. For a variety of reasons, in
disciplines as diverse as physiology or medicine,
psychology, and communication engineering, discussion
of hearing and its disorders has taken second place
to that concerning vision. Although improving, that
predicament still exerts a restrictive effect upon
related applied fields.
As Davis* chapter shows, hearing disorders are
common enough to justify an attempt to encourage a
better professional and lay understanding of their
forms and origins. The other contents of the book
also reflect a concern with the high prevalence of
hearing problems. But there are important areas of
study concerned with treatment of conductive
disorders and habilitation in pre-lingual deafness
that we have had to omit. We have also omitted
detailed reference to the effects of noise on
hearing. Although some details and synergisms remain
to be worked out, these effects have been generally
established for some 20 years; their implications
are becoming applied in routine fashion in
medico-legal work and disability compensation within
the developed world and convenient sources exist. On
the other hand to provide insight into the disabling
effects of hearing impairment, we have introduced and
built upon important insights in speech communication
vi Preface
that have been accumulating since the 1950s, but
which have not been assimilated into thinking about
hearing disorders. The chapter by Bailey, and to a
lesser extent those by Cowie and Douglas-Cowie, by
Summerfield and by Haggard attempt to provide this
particular foundation. We have been particularly
concerned to avoid the pathological fallacy - the
distortion of or absence of understanding of normal
functioning from concentration upon disorders that
are experienced as severe enough to lead people to
seek help. So there are many references to research
with normally hearing listeners in addition to Davis1
report of a study of the population at large.
Overall improvements in hygiene, nutrition and
health have increased the numbers of elderly people;
but there appears to have been no appreciable impact
yet of improved general health upon the prevalence of
sensorineural hearing disorders in the elderly, and,
with millions of elderly people taking diuretics and
other drugs continuously, the reverse may even be the
case. A large number of health professionals
consequently need to know something about disorders
of hearing even if their prime responsibility does
not lie in that specialised domain. To make this
book useful to the teachers of those non-specialised
professions we have tried to avoid the assumptions
and jargon of any one profession. The book has been
planned to be of value to first degree students, to
academic and professional workers concerned with
hearing, speech, and their disorders, and to
scientifically or medically literate people
generally. This scope has the further consequence
that any professional group describing itself as
"clinical" is likely to perceive this as a
"non-clinical" book, as it is not concerned with day
to day recipes for clinical practice. For the lack
of a clinical orientation in that narrow sense we
make no apology, because we perceived a need for a
book that had to be unconventional in relation to
conventions of any particular clinical profession.
Some standard themes that might be obligatory in
an audiology textbook have had to be omitted here.
Lutman's chapter, concerned largely with audiological
tests, does however provide necessary background for
non-audiologists, on what audiology is and does.
"Audiology" is the post-war American neologism for
the professional discipline concerned with hearing
disorders and, to some extent, hearing science.
Although many of our chapter authors have contributed
to the contemporary development of British audiology
we have kept the use of the term "audiology" to a
Preface vit
minimum and have largely restricted discussion of
particular professional roles to a single chapter
that of Stephens. The main reason for this is that
professional involvements and structures differ so
much between countries while the needs for which they
cater differ little. For example in most of Europe
except the UK "audiologist" implies a medically
gualified person, in North America it implies the
reverse, while in the UK, unless further specified,
the term is ambiguous in this respect. This
diversity also entails that no strong suggestions can
yet be made about the levels of education for which
audiological knowledge would best be packaged, nor,
according to what vertical demarcation into medical,
scientific, psychological, engineering or technical
spheres it should be divided. The need for
multi-purpose books such as this one will therefore
be with us for some time to come.
Research and development activity related to
health constitutes a small fraction of the huge
expenditure on health in most Western Countries.
Many researchers, government officials and
politicians are concerned nowadays about the
application of research. It would be reassuring to
learn that what has been established by research
becomes rapidly and safely applied in new procedures
for prevention, diagnosis or treatment, in new
equipment and drugs, and i' efficient allocation of
health resources. Alas, ^.his is not always so
because professional training is unfairly burdened
with the major responsibility of channeling new
knowledge into application. This is not the place to
suggest further channels, which in any case would
have to take account of particular national patterns
for professional training and service delivery. We
can however offer this book as an indication that a
channeling problem exists. One of its central
themes, loss of frequency resolution, is a concept
with a modern history of 12 years, but it is still
unfamiliar to the majority of practitioners in the
field of hearing disorders. In this respect, the
book should be regarded as setting a style for a
decade's development and application in
scientifically based audiology, and to some extent
for further research. We hope that it also makes
doctors and scientists generally aware that hearing
research has some interesting and creditable
achievements.
M.P. Haggard
November 1982
Editorial Note
In coming to terms with hearing science and hearing
disorders the reader will have to span a wide range
of concepts from several disciplines. We have
provided encouragement in terms of a glossary and we
hope that he or she is rewarded with an appreciation
of the fertile quality of contemporary hearing
research.
It may help the reader in selecting a suitable
sequence of chapters to appreciate the editors'
intentions in the arrangement of chapters. Those of
Bailey, Davis and Evans set the scene, giving
necessary background respectively in the nature of
speech communication, the extent of hearing problems
and the pathophysiology of hearing. Four core
chapters follow in which are covered four areas of
central importance to understanding hearing disorders
and their effects; among these the degree of
emphasis on current research in relation to accepted
background varies considerably, as demanded by the
maturity of the specific area of enquiry. They cover
assessment of auditory function, (Lutman), the scope
for technological solutions, (Haggard), the nature of
audio-visual speech perception, (Summerfield), and
the effects of deafness upon speech production,
(Cowie and Douglas-Cowie). Discussion of the
much-publicised "cochlear implant" is located in its
proper context as an aid to lipreading that may be
highly beneficial in some of the rare cases of
profound or total deafness. Finally a clinical
framework within which the accumulating knowledge can
be and is already becoming applied is outlined by
Stephens.
We should like to record our gratitude to the
following staff of the Institute of Hearing Research
for their devotion and application in the production
of the camera-ready typescripts: Pamela Smith
(style, checking, format and scheduling); Jean
Willoughby and Karen Heartfield (inputting, draft
production and ammendment); and Tim Folkard
(word-processing software). Cath Pettyfer of
Academic Press was a most helpful guide on style,
convention and production. It is a statistical
certainty that some mistakes remain; for these the
responsibility is ours.
M.E.Lutman
M. P.Haggard
List of Contributors
Dr. P.J. Bailey Lecturer, Department of
Psychology, University of York, Heslington, York,
Y01 5DD.
A.C. Davis Research Scientist (Statistician), MRC
Institute of Hearing Research, University Park,
Nottingham, NG7 2RD.
Professor E.F. Evans Professor of Auditory
Physiology, Head of Department of Communication
and Neuroscience, University of Keele, Keele, ST5
5SG.
Dr. M.E. Lutman MRC Scientist-in-Charge, Nottingham
Clinical Outstation of the Institute of Hearing
Research, General Hospital, Nottingham, NG1 6HA.
Dr. A.Q. Summerfield Research Scientist (Speech
and Hearing), MRC Institute of Hearing Research,
University Park, Nottingham, NG7 2RD.
Dr. R. Cowie Lecturer, Department of Psychology,
The Queen's University of Belfast, BT7 INN.
Dr. E. Douglas-Cowie Lecturer, Department of
English, The Queen's University of Belfast, BT7
INN.
Professor M.P. Haggard Special Professor of
Audiological Science, University of Nottingham and
Director, MRC Institute of Hearing Research,
University Park, Nottingham, NG7 2RD.
Dr. S.D.G. Stephens Consultant in Audiological
Medicine, Department of Auditory Rehabilitation,
Royal National Throat, Nose and Ear Hospital,
Gray's Inn Road, London, WC1 8LD.
1 Hearing for Speech: the Information
Transmitted in Normal and
Impaired Hearing
Peter J. Bailey
Contents
I. INTRODUCTION
II. WHAT FORMS CAN LINGUISTICALLY RELEVANT
INFORMATION TAKE?
III. ARTICULATORY AND ACOUSTIC BASES FOR PHONETIC
CONTRASTS
A. Acoustic theory of speech production
B. Acoustic correlates of articuiatory dimensions
IV. REPRESENTATIONS OF ACOUSTIC AND AUDITORY
SPEECH PATTERNS
V. PROPERTIES OF HEARING IMPAIRMENT RELEVANT TO
SPEECH PERCEPTION
VI. DIVISION OF LABOUR BETWEEN PERCEPTION AND
PRODUCTION FOR EFFICIENT SPEECH COMMUNICATION
VII. SPEECH PERCEPTION IN HEARING IMPAIRED LISTENERS
VII I. CONCLUDING SUMMARY
I. INTRODUCTION
There are grounds for believing humans to be
specialised for speech communication - most evidently
for speech production by virtue of the shape and
flexibility of movement of the vocal tract and its
articulators. Parallel specialisation for speech
perception would be plausible despite the absence of
extensive experimental evidence for perceptual
specialisation (Repp, 1982). More generally, there
is no compelling evidence against the formal
uniqueness of human linguistic behaviour (MacPhail,
1982). The implications of these points are: first,
evolutionary pressures have rendered speech an
efficient vehicle for linguistic communication
(Lieberman, 1973), and secondly, speaker/hearers
appear to be specialised to produce and perceive
2 P. J. Bailey
linguistic information in this form. Second, evolu-
tion of human culture has since made speech the main
reason we have for hearing. To the extent that these
observations are true it would seem perverse not to
attempt to maximise access to speech for hearing-
impaired people before trying other rehabilitative
measures.
Several characteristics of speech render it an
efficient code for the particular communicative role
it serves. It can support high rates of information
flow by contrast with writing and reading
(intelligibility falls significantly only when speech
rates exceed about 160 words per minute), but it is
flexible enough also to allow the other extreme in
trading off speed against accuracy, as when people
pronounce clearly and slowly a crucial,
unpredictable, or rare word, or a proper name. The
redundancy which permits these high rates also
ensures substantial resistance to the masking effects
of extraneous noise, so that speech remains
intelligible despite considerable distortion or
signal-to-noise ratios worse than 0 dB. Speech is
well adapted to carry extra-linguistic information
such as emphasis and emotional content by means of
variations in pitch, loudness and rhythm. Speech
also provides meta-communicative cues such as those
which cede or deny the floor to another interlocutor;
these facilitate fluent conversation. At a more
practical level, there is clear virtue in a mode of
communication which leaves hands, feet and limbs free
for other skilled behaviour. For all these reasons
there is good justification for expressing our
understanding of hearing impairment in specific
relation to the requirements of understanding speech.
Traditionally in audiology this has only been done in
a rather notional way, on which recent developments
in the acoustical control of test materials have
begun to improve (e.g. Fourcin, 1980).
Much of the handicap of hearing impairment
derives from a single intervening disability - the
failure to understand speech easily, particularly
when listening in a noisy environment. A common
report from hearing-impaired people is that they can
hear speech but cannot understand what is being said.
My two main aims in this chapter are to characterise
the main types of linguistically significant
information present in speech, and to establish a
basis for discussion of some factors which contribute
to poor speech perception in hearing-impaired people.
A complementary chapter (Summerfield, 1982; this
volume) considers the limitations on, and
Hearing for Speech 3
implications of, speech perception using additional
information derived from senses other than hearing
primarily vision.
Ideally we might begin with a description of the
process of speech understanding in normal hearing
listeners. In that way drawing on data on hearing
f
impairment we might be able to deduce the effects of
hearing impairment on speech processing and discuss
the results of experiments which test such
predictions. In a statistical fashion this has been
done (see Haggard, 1982; this volume). But these
purely quantitative formulations make no reference to
the specific classes of information within speech or
to the processes by which the information is analysed
and interpreted and so, despite their usefulness,
offer no element of explanation. Only with such
understanding can hope be entertained of an effective
approach to disability assessment, hearing aid
design, and training in hearing tactics.
Unfortunately, in spite of a considerable body of
data on the relationships between speech production,
speech acoustics and speech perception, there exists
no adequate account of normal speech understanding
that embraces the complex relationships reported and
qualifies as a genuine "theory". I shall
concentrate, therefore, on a more descriptive level,
clarifying the principles governing the form of
acoustical patterns resulting from activities of the
vocal apparatus, and examining how these patterns
carry linguistically significant information for the
listener. Many of the experiments I shall refer to
have used listeners with normal hearing; this is in
part because such experiments are the majority, but
also because there are reasons to believe that
improvements in auditory prostheses are now likely to
follow from a better overall understanding of normal
speech processes (Haggard, 1982; this volume). My
general strategy will be to attempt to rationalise
the patterns of speech perception deficits that are
characteristic of certain kinds of hearing
impairment, particularly hearing loss of sensori-
neural origin acquired post-lingually. Specifically,
I shall comment on the relative efficacy with which
various significant acoustical properties of speech
are preserved in the listener's impaired auditory
system.
