This dissertation has been microfilmed exactly as received SHALLOP, Jon Kent, 1939- A STUDY OF ACOUSTIC IMPEDANCE AND MIDDLE-EAR FUNCTION.
The Ohio State University, Ph.D., 1965 Speech-Theater
University Microfilms, Inc., Ann Arbor, Michigan A STUDY OF ACOUSTIC IMPEDANCE
AND MIDDLE-EAR FUNCTION
DISSERTATION
Presented In Partial Fulfillment of the Requirements of the Degree Doctor of Philosophy In the Graduate School of The Ohio State University
by-
Jon Kent Shallop, B .S ., M.A,
The Ohio State U n iversity
1965
Advisers Department of Speech VITA
December 21 , 1939 Born - Erie, Pennsylvania.
1961 B.S. Ed., Edinboro State College Edinboro, Pennsylvania
1961-1963 Instructor of Speech, Edinboro State College
1963 M.A., Kent State University
1963-1964 Communications Fellow , The Ohio State U n iv e rs ity , Columbus, Ohio
1964-1965 United States Public Health Service Train ee, The Ohio S tate U n iv e rs ity .
ii TABLE OF CONTENTS
Page
VITA ...... II
TABLE OF CONTENTS...... i l l
LIST OF TABLES...... Iv
LIST OF FIGURES ...... v
CHAPTER r—
I INTRODUCTION ...... 1
The Problems ...... 4 Nul 1 Hypotheses ...... h D e fin itio n s of Terms ...... 5
II REVIEW OF THE LITERATURE...... 10
Function of the Middle Ear ...... 10 Function of the Middle-ear Muscles ...... 15 Measurement o f Acoustic Impedance ...... 22 Otosclerosis and Stapedectomy ...... 29
111 INSTRUMENTATION AND PROCEDURES ...... 36
Selection of Subjects ...... 36 Instrumentation ...... 37 Procedures ...... J+3
IV RESULTS AND DISCUSSION...... 52
Hypothesis 1: Acoustic Impedance Measures ...... 52 Hypothesis I I ; Hearing S e n s itiv ity and Impedance .... 72 Hypothesis III: Acoustic Reflex Time Delay ...... 76
V SUMMARY AND CONCLUSIONS...... 80
APPENDIXES
A Test-retest Measures of Acoustic Impedance ...... 83 B Raw Scores fo r Normal Hearing Subjects ...... 85 C Raw Scores fo r Stapedectomized Subjects ...... 89 D Raw Scores for Otosclerotic Subjects...... 93 E Raw Scores of Relative Air-bone Gap ...... 97 F Raw Scores for Acoustic Reflex ...... 98
BIBLIOGRAPHY ...... 99
H i LIST OF TABLES
Table Page
1. A lis tin g of means, standard deviatio n s, and medians determined from the measures of Impedance, compliance, and resistance for ail subjects ...... 56
2. Values associated with J>tests showing the differences between the comparisons o f mean measures of equivalent compliance obtained from all subjects ...... 64
3* Values associated with J:-tests showing the differences between the comparisons o f mean measures of a rb itra ry resistance obtained from all subjects ...... 66
4 . Values associated with Jt-tests showing the differences between the comparisons o f mean measures of to ta l impedance obtained from all subjects ...... 67
5* H-values associated with the Kruskal-Wal1 Is one-way analysis of variance showing the differences between the compari sons of mean measures o f to ta l impedance, compllance, and resistance obtained from all subjects ...... 70
6. Spearman rank correlation coefficients for test retest compliance and resistance measurements ...... 84
iv LIST OF FIGURES
F ig u re Page
1. Schematic representation of mechanical impedance as a function of frequency ...... 7
2. A drawing of the middle ear ...... I I
3. A schematic cross-section drawing showing the close approxi mation of the stapes footplate within the oval window of the Inner e a r ...... 14
4. Schematic cross-section drawing of the Zwislocki Acoustic B r id g e ...... 23
5 . Comparative impedance measures fo r one ear without an incus, one normal e a r, and one ear diagnosed as oto sclerosis • 26
6. Schematic drawing of the stapes and three replacement prostheses ...... 3]
7* Instrum entation fo r the measurement o f acoustic impedance . . 38
8 . The Zwislocki Acoustic Bridge with the monitoring stethescope...... 39
9 . Instrum entation fo r the measurement of an acoustic r e fle x , shown schematically...... 40
10. Cai ibration of the noise stimulus as viewed on an oscilloscope screen ...... 43
11. A schematic diagram showing the analysis of instrumentation time delays fo r the measurement o f an acoustic re fle x as detected by a change of acoustic impedance ...... 44
12. Placement of the ear speculum fo r the measurement of ear canal volume ...... 47
13* Measurement o f the ear canal volume p rio r to the measurement of acoustic impedance ...... 47
14. The Zwislocki Acoustic Bridge in position for the measure ment of acoustic impedance ...... 48
15* The apparatus used for supporting the acoustic bridge during the recording of the acoustic reflex response . • 50
v LIST OF FIGURES ( c o n t.)
F ig u re Page
16. A graph showing the re la tio n s h ip between the equivalent volume measurements obtained w ith the Zwislocki Acoustic Bridge and re a c tiv e acoustic impedance in acoustic ohms...... 54
17. A graph showing the re la tio n s h ip between the a rb itra ry resistance measurements obtained w ith the Zw islocki Acoustic Bridge and resistive impedance in acoustic o h m s ...... 55
18. Median scores of to ta l impedance fo r the three subject groups shown graphically as a function of the four test frequencies ...... 58
19. Mean scores of total impedance for the three subject groups shown graphically as a function of the four te s t frequencies...... 60
20. Median scores of compliance and resistance for the three subject groups shown graphically as a function of the four test frequencies ...... 6 1
21. Mean scores of compliance and resistance for the three subject groups shown graphically as a function of the four test frequencies ...... 62
22. A s c a tte r diagram of measures of to ta l impedance vs. relative air-bone gap obtained from all subjects at 250 c p s ...... 73
23. A s c a tte r diagram of measures of to ta l impedance vs. relative air-bone gap obtained from ail subjects a t 500 cps ...... 7k
2A. Examples of sing le impedance change responses from one normal h e a rin g -s e n s itiv lty subject and one stapedectomized subject ...... 77
vl CHAPTER I
The purpose of this study was twofold: (a) to investigate some aspects of acoustic impedance measured at the eardrum of subjects w ith normal-hearing sensitivity, subjects with otosclerosisJ and subjects after stapedectomy surgery; and (b) to study the reflexive responses of the mlddle-ear muscles of some subjects during stimulation of their contralateral ear with acoustic noise.
It Is acknowledged that a function of the middle ear is to transmit sound energy to the Inner ear. As reported by Lawrence (34) t
Hu'ller (54) published a description of an apparatus in 1840 that was used to simulate the functioning of the middle ear. With this mechanical-fluid model, he demonstrated the importance of the middle ear by removing the analagous middle-ear structures. This manipulation resulted in decreased pressure within the inner ear of the model.
Helmholtz (26) also described the pressure-transfer function of the middle ear in 1863:
The mechanical problem which the apparatus within the drum of the ear had to solve, was to transform a motion of great amplitude and l i t t l e fo rc e , such as impinges on the drum- skin, Into a motion of small amplitude and great force, such as had to be communicated to the la b y rin th .
Altmann (2) defines otosclerosis as "a primary, often bilaterally symmetrical, disease of the bony labyrinthine capsule, in which circum scribed destruction of the capsule at certain typical places is followed by the formation of foci of new, at firs t very immature, bone.*'
1 Investigations of middle-ear function in recent years have confirmed the ideas of Muller and Helmholtz. Bek&sy (7) quantified the pressure-transformation function of the middle ear using cadaverous temporal bones. Under these conditions, he determined that the sound pressure at the oval window of the inner ear was increased by a factor of 22 as compared w ith th at a t the tympanic membrane. Wever and
Lawrence (84) studied the cochlear microphonic sensitivity in cats before and after the middle-ear ossicular chain was removed and reported an average sensitivity decrease of 28 dB over a wide-frequency range.
Schuster (67), Metz (42) , and Zwislocki (89) have described a mechanical device that determines the efficiency of the middle ear without requiring an overt response from the subject. This instrument is commonly referred to as an acoustic bridge, being somewhat similar to the e le c tric a l Wheatstone Bridge in th a t both compare impedances.
The mechanical acoustic bridge that was employed in the present study, as well as other electro-acoustic impedance bridges, w ill be discussed in the next chapter.
Many writers (16, 17* 27, 31, 42, 77, 78, 89) have recommended the use of measures of acoustic impedance in the diagnosis of hearing disorders. To date, however, this procedure has not been routinely utilized in the United States.
Based on measures obtained with acoustic bridges, normal and some pathological ears have been reported as having characteristic impedance functions (42, 8 6 ). When compared with normal ears, otosclerotic ears show higher than normal Impedance measures. On the other hand when the ossicular chain is discontinuous, lower impedance measures may re s u lt.
Acoustic bridges have also been used to detect the a c tiv it y of the middle-ear muscles, the stapedius and the tensor tympani, as reported by Metz (40) , Miller (46, 47, 50, 51), Terkildsen ( 78),
Klockhoff (30), Feldman (17), Djupesland (12), Dali os (11), and Lilly and Shepard (3 6 ). These workers have discussed normal and abnormal reflexes of persons with normal-hearing sensitivity, otosclerosis, and facial paralysis.
Middle-ear muscular activity can also be detected by recording relative pressure changes at the tympanic membrane with a manometer.
Weiss and others (81) reported several findings including a response from a subject without a stapedius muscle which is generally considered to be the major contributor to the acoustic reflex. It was postulated that the response from this subject represented the contraction of the tensor tympani muscle.
In regard to the function of the tensor tympani muscle, Perlman
( 63) stated that a reflex response to acoustic stimuli cannot be detected by a change of impedance from persons with a stapedectomized ear since the tendon of the stapedius muscle has been severed. Klock hoff and Anderson (32) have Indicated that a change of acoustic impedance could be obtained from persons with stapedectomy only when an airstream was directed at the subject's eye. This response was thought to represent the contraction of the tensor tympani muscle. 4
The problems
The problems investigated in the present study consisted of three related aspects of middle-ear function. First, whether or not measures of acoustic impedance can be used to d iffe r e n tia te among the m iddle- ear functioning of subjects with (a) normal-hearIng sensitivity,
(b) presumed otosclerosis^, and (c) stapedectomy. Second, a study was made of the relationship between acoustic Impedance and the relative difference in hearing sensitivity for bone-conducted and air-conducted signals (air-bone gap). Third, the latency of acoustic reflexes stimulated by noise in the opposite ear was studied for some subjects with normal-hearing sensitivity and some of the stapedectomized subjects.
Nul1 hypotheses
The following hypotheses were formulated and tested as a part of the present study;
1. There Is no difference between the acoustic-Impedance measures for pairs of subject groups with (a) normal-hearing sensitivity and otosclerosis, (b) normal-hearing sensitivity and stapedectomy, and
(c) otosclerosis and stapedectomy.
2. There is no relationship between the acoustic-Impedance measures and the relative difference between air-conduction and bone-
9 The term “o to sclerosis" is used by th is w rite r in recognition that diagnosed otosclerosis cannot be assumed to be a pathological con dition until confirmation during surgery and/or histological analysis. Subsequently the word otosclerosis w ill be used alone to indicate this semantic awareness. conduction sensitivity for subjects with (a) normal-hearIng sensitivity, (b) otosclerosis, and (c) stapedectomy.
3. There is no difference between the delay of a change in acoustic impedance in response to a noise stimulus in the c o n tra la te ra l ear for subjects with (a) normal-hearing sensitivity and (b) stapedectomy.
Definition of terms
1. Acoustic impedance. Impedance, whether mechanical, electri cal, or acoustical, consists of "real" and “ imaginary" components.
The real part is resistance, analagous to a resistor in an electrical c ir c u it . The Imaginary component is c alled reactance and includes compliance and mass. The la t t e r two facto rs are analagous res p e c tiv e ly to a capacitor and an inductor in an electrical circuit.
The imaginary component of impedance is so named because i t can not be combined w ith the real component by simple a d d itio n . R ather, these terms must be treated as a complex function, that is, they can only be combined into one measure by a procedure such as vector a n alysis.
Vector analysis Is based on geometric principles and according to
Rush (65) the rule for this procedure Is the parallelogram law.
Applying this rule to vector analysis Rusk states:
The res u lta n t of two or more forces is th a t s in g le fo rce which would have the same effect as the individual forces acting together, if it replaces them.
By analogy if a car was going through a sharp curve at a high rate of speed, in this instance the resultant vector would not be the direction of momentum, which would actually direct the car off the road; rather it would be the direction In which the car successfully manages the curve, in other words, the forward momentum and the turning of the fro n t wheels combined to form a re s u lta n t v e c to r, namely, the negotia tion of the curved road.
Returning to impedance, the real component (resistan ce) is
independent of frequency in that it deters all frequencies In a similar manner. On the other hand, the imaginary component (reactance) is frequency dependent. In a mechanical-acoustical system, such as the middle ear, reactance is controlled by compliance below the resonant frequency. Beyond the resonant frequency, the middle ear reactance consists mainly of mass.
Zwislocki (89) presents the following formula for acoustic
impedance:
Za - £ = Ra + j (2TTfMa - 1 ) , v 2irfca
where P means sound pressure, V - volume velocity, Ra - the acoustic resistance, Ma - the acoustic mass, and Ca - the acoustic compliance.
The symbol (j) in this formula indicates that the two terms (resistance and reactance) cannot be algebraically added; however, they can be combined by vector analysis. M iller (51) has shown such a solution
in a vector diagram for mechanical Impedance, /Zm/, ss 1° Figure 1.
Resistance is represented on the abscissa and reactance is represented on the o rd in a te . The res u lta n t vector / Z / is the to ta l impedance o f the simple mechanical system illu s tra te d in the same fig u re . The Impedance m ------► | m |— A / \ W — | m
m CM
Figure I. Mechanical impedance as a function of frequency is repre sented schematically. The terms shown in this figure are as follows: /Z/ = total impedance, Rn, » resistance, X = total reactance, S/27Tf =* stiffness reactance, 27TfM = mass reactance, and d = the res u lta n t phase-angle difference between the driving force (F) and the mass velocity (V). Adapted from Mdller (51).
is determined according to the Theorem of Pythagoras for any 90-degree
tria n g le :
A2 = B2 + C2 , o r A - \Jb2 «* C2 , when B and C represent the two sides of the triangle which form the
90-degree angle and A is the hypotenuse of the triangle. 8.
Metz (^f2) , Zwislocki ( 89), and Miller (51) reported that acoustic
Impedance fo r the ear is related to mechanical impedance by the following formula in which Za represents acoustic Impedance, Zm mechanical Impedance, and A the effective area of the eardrum:
Za = Zfj/A . The basic unit of measure of acoustic impedance Is the acoustic ohm.
2. Acoustic ohm. The American Standards Association (ASA) (3) defines an acoustic ohm as follows:
An acoustic resistance, reactance, or impedance has a magnitude of one acoustic (cgs) ohm when a sound pressure of 1 microbar produces a volume velocity of 1 cubic centi meter per second.
3. Normal-hearing sensitivity. A subject with normal-hearing sensitivity had detection thresholds for air-conducted pure-tone signals that were less than + 10 dB (1951 ASA standards) for the fre quencies 250, 500, 750, and 1000 cps. The subjects did not have a history of middle-ear Infections or middle-ear surgery. In addition, there was not in evidence any scar-tIssue on, or, perforations of, the eardrum of the measured ear.
Jt. Stapedectomy. Any person who had been operated for otoscle rosis with the complete or partial substitution of a prosthetic device for the stapes bone was considered eligible for this study provided the surgery had been performed a t le a s t s ix weeks p rio r to the measurement of impedance and he had no p erfo ratio n s in his ear drum.
5. OtosclerosIs. Persons diagnosed by an otologist as having
"otosclerosis" were presumed to have this disease. 6* Acoustic reflex. Acoustic reflex Is defined as a definite change of acoustic impedance, as measured from tracings from a graphic-
level recorder connected to an acoustic bridge. The stimulus for this response was an 88 dB, re 0.0002 dyne/cm^ sound pressure level (SPL) , white-noise signal in the contralateral ear of the subject. The
latency of this response was quantified in msec.
7. Acoustic bridge. For this study the Zwislocki Acoustic
Bridge (Model 3) was utilized. This instrument yields data that can be expressed as acoustic ohms.
Organization of this study
In the firs t chapter, an introduction to the concept of acoustic
impedance has been presented. A statement of the problem, the null hypotheses, pertinent definitions, and the plan for this study conclude the chapter.
In Chapter II, a review of the literature w ill be presented.
The experimental procedures and instrumentation w ill be presented and discussed in Chapter ill. The fourth chapter includes a presentation and discussion of the results of the investigation. Chapter V summarizes the study and presents conclusions based on the results. Certain recommendations for additional research are also included in the last chapter. CHAPTER I I
REVIEW OF THE LITERATURE
Function of the middle ear
The function of the middle ear seems to be to conduct sound to the cochlea. According to B4k4sy and Ronsenbiith (8) the understanding of this function began with the anatomical descriptions of the middle- ear structures during the sixteenth century. During that period the ossicles, the middle-ear muscles, the Eustachian tube, and the two divisions of the inner ear (labyrinth and cochlea) were identified.
Functionally it was thought that perhaps the middle ear conducted sound to the inner ear which was filled with 'Implanted a ir.1 According to
Wever (82) two pathways to the inner ear were recognized by Colter (9) in 1573, (a) via the ossicular chain to the oval window, and (b) through the air of the middle-ear cavity to the round wtndow. Figure 2 may aid the reader in visualizing these structures.
In the seventeenth century DuVerney recognized the two approaches to the cochlea. He emphasized the importance of the three ossicles while s till adhering to the belief of 'implanted a ir1 within the cochlea
(82). Duverney also proposed what was possibly the firs t theory of hearing, based on resonances within the inner ear that excited the inner ear.
10 Figure 2, A drawing of the middle ear showing the ossicles and the loci of Insertion of the tendons of the tensor tympani muscle and the stapedius muscle (o rig in a l) The concept of air within the cochlea was shown to be false during the next century. According to Bekesy and Rosenblith (8), Valsalva was the firs t person to indicate the presence of fluid within the inner ear.
However, he s till contended that air must be present in order for sound to be perceived. Wever ( 83) reported th a t Cotugno (10) and Meckel (*40) confirmed the inner ear to be filled with fluid, presenting a new problem for investigation, the transmission of sound from air to a fluid medium. This la tte r function was reported by M uller in 1840 (54) and by one of his students, Helmholtz, in 1863 (26).
The work of Helmholtz (26) emphasized the importance of the middle ear as a conductor of vibrations to the Inner ear. He recognized some of the mechanical problems that were inherent in the transfer of energy from a low-density to a high-density medium. The successful tran s duction of sound energy in air, lateral to the eardrum, into pressure variations within the cochlear fluids was attributed to the complex movements of the eardrum and to the lever action of the ossicles.
Detailed information concerning the functions of the middle ear has been advanced considerably during the present century by the research 1 1 o f Bekesy ( 7 ). He has demonstrated th at the middle ear has an am pli fying pressure-transformation value of 22 (times greater than the input) which was determined by dividing the effective area of the eardrum by the area of the stapes and multiplying this quotient by the lever ratio of the ossicles. In addition, he has shown that the fluid behind the stapes is set into motion and thereby transmits the usually complex vibrations of sound along the cochlear partition as traveling waves. 13
These complex waves then stimulate the receptor hair cells along the basilar membrane in a manner not yet understood. i i Bekesy (7) used temporal bones of cadavers and determined th at the absence of the middle-ear structures, i.e. the ossicles, resulted in a decrease of the effective mechanical-pressure transfer to the inner ear. This decrement was equivalent to an average hearing loss of approximately 55 dB from 250 cps to 3000 cps. Wever (83) obtained similar results reporting an average intensity loss of 42 dB in cats, using the cochlear microphonic procedure as a criterion measure. In another study, Wever and Lawrence (84) demonstrated a less severe loss of 28 dB In the hearing sensitivity of cats when sound stimuli were directed through a flexible tube to the stapes footplate in the oval window rath er than being directed In to the e n tire open middle e a r.
This latter procedure (flexible tube) reduces the effect of phase can c e lla tio n , since sound waves th a t impinge upon the oval window and the round window simultaneously can re s u lt in phase c a n c e lla tio n of the pressure waves.
According to Bekesy ( 7 ) , the fo o tp la te of the stapes must provide adequate closure of the oval window to prevent a loss of pressure as illustrated in Figure 3* He indicated that the maximum width of the annular ligament circumscribing the footplate of the stapes is .1 mm and that if the clearance between the footplate and the perimeter of the oval window is excessive, the transfer of sound to the inner ear is reduced due to a backset of fluid pressure. In a similar vein Wever
(83) compared the motion of the stapes with the piston of an engine. INNER MIDDLE IN N E R - _ MIDDLE EAR EAR EAR - . EAR -V FLUID FLUID “
STAPES
Figure 3* A schematic cross-section drawing showing the close approximation of the stapes footplate within the oval window of the Inner ear and the resultant backset of fluid pressure when the stapes replacement is too small. Adapted from B4k£sy (7). 15.
This analogy for the motion of the stapes is not entirely correct since
the stapes pivots about the posterior margin of its footplate. Onchi
(59) has attributed this movement to the stiffness of the posterior margin of the supporting ligament. Be'kesy (7) has pointed out two
ro tio n al axes of the stapes, one a t low and one a t high in te n s itie s , due to the influence of the stapedius muscle. This and other functions of the middle-ear muscles are described in the following section.
Function of the middle- ear muscles
Two muscles Influence the transmission of sound through the normal-functioning middle ear of man, the tensor tympani, identified by Eustachio in 156^* and the stapedius, described by Varolius in 1591
(8, 29). Only the tendons of these two muscles can be found in the middle-ear cavity since the muscles are encased in bony canals. Bekesy
(7) has stated that the enclosing of these muscles probably prevents sub-harmonic distortions by damping the ossicular chain. Morphologically these two muscles are almost d ia m e tric a lly opposed and perpendicular to the main axis of ossicu lar v ib ra tio n (2 9 ). The stapedius tendon inserts
Into the neck of the stapes and the tendon of the tensor tympani inserts into the neck of the malleus (See Figure 2).
The a c tiv ity of the m iddle-ear muscles has been noted by Simmons
( 72) in responses to (a) acoustic stimuli, (b) physiological activity independent of acoustic stim uli, and (c) other stimuli that evoke reflex activity. Mundie (56) has theorized that the middle ear acts as an impedance-matching transformer with variable characteristics which are dependent on normal and pathological physiological conditions. 16 ,
These views seem to represent opinions that are to be contrasted with
less contemporary ideas that the middle-ear muscles respond mainly to
intense sounds ( 3 8, 4 2 , 6 2 ).
Middle-ear reflex. A review of the literature does not reveal a complete description of middle-ear reflex responses. Weiss and his co-workers (81) have pointed out th at research has not confirmed th at
the tensor tympani muscle responds to acoustic stim uli, as the stapedius muscle obviously does. Some researchers have indicated that tactile and acoustic stimuli can e lic it responses from both middle-ear muscles.
These points are discussed in the following paragraphs.
Luscher, in 1929, described an acoustic reflex of the stapedius muscle (39). Using a microscope, he viewed the middle ear of an
individual with a perforated eardrum while the opposite ear was stimu
lated acoustically. Since this report, numerous observations of this reflex have been made. Galambos and Rupert (22) studied the acoustic reflex in cats. They showed that acoustic stimulation resulted in a response mainly from the stapedius muscle with an Ipsilateral and contralateral delay of 10 msec; the tensor tympani contracted also, but only after a delay of about 50 msec.
One function of the middle-ear muscles may be to protect the ear from Intense acoustic stimuli. Protection might be afforded by an
increased stiffness of the tympanic membrane which, in turn, would reduce the sound energy reaching the inner ear. Such protection would 17. be dependent on the latency of the muscle contractions; a shorter time delay between stimulus and response would allow less to ta l energy to
reach the Inner ear.
Jepson (29) summarized the resu lts from several Investigators in a
report that the latency of the acoustic reflex in man is about 10 msec for the stapedius muscle and longer for the tensor tympani muscle. ■ t Bekesy (7) indicated that this delay of 10 msec for the acoustic reflex
is not s u ffic ie n t to protect the ear from damage, and that the ear is
largely protected by the nature of the rotational axis of the stapes.
Below the threshold of feeling, the stapes rotates with a vertical axis about its posterior footplate edge (see Figure 2); as the sound inten sity increased, the action of the footplate changes to a horizontal axis of rotation.
Stimulus intensity and the acoustic reflex. Several investiga tors have studied the action of the middle-ear muscles as a function of various intensity levels rather than merely determining the latency of the acoustic reflex. Dal 1 os (11) as well as L illy and Shepard (36) demonstrated that the acoustic reflex in man is a graded response dependent on the intensity of the stimulating noise in the opposite ear.
Furthermore their results indicated that there is not a noticeable degree of adaptation at high-intensity levels.
Weiss and others (81) described a “ramp function" response to the increasing intensity of an 800 cps tone. They utilized a pressure- s e n s itiv e apparatus and detected negative impedance changes fo r some subjects and p o s itiv e changes fo r others. These responses were always graded functions. 18 .
With a bilateral impedance-detection apparatus, M iller (50) reported the results of a comprehensive study of the acoustic reflex in man. Among other things, he described the bilateral impedance changes in response to 2 dB increments of a bandpass-filtered noise stimulus (center frequency of 1^50 cps). The results confirmed the notion that the acoustic reflex is a graded response which increases in amplitude as a function of increased intensity of the noise. It was also established th at the latency o f the impedance change decreased as the intensity of the stimuli increased.
Responses of the tensor tvmpan1 muscle. Concerning whether or not the human tensor tympani responds to acoustic stimulation, Perlman
(63) stated:
Acoustic contraction of the human tensor tympani muscle has not been observed directly or indirectly through acoustic impedance measurements. When the stapedius tendon is c u t, no impedance change can be induced by acoustic stimuli in man.
Klockhoff (31) stated th at the tensor tympani does not respond to acoustic stimulation and demonstrated that this muscle will respond to tactile stimulation (an abrupt airstream directed at the eye indepen dently of the person's ability to hear).
Ojupesland (12) obtained results similar to those of Klockhoff by stimulating the opposite ear with an airstream. These responses to tactile stimulation were obtained in part from persons who did not respond reftexively to acoustic stimuli. He also reported "small impedance changes11 In response to acoustic s tim u li fo r two persons after stapedectomy, even though in a later report (13) he stated that 19.
only the stapedius muscle contracted in response to sound. In this
same article (3) he indicated that the tensor tympani responded only in
conjunction with a startle response which included the contraction of
the periorbital muscles.
Experimentation gf middle-ear muscular function. A procedure for determining the function of the middle-ear muscles was described by
Weiss and others (81) who used a manometer to detect a change of a ir pressure in the ear canal. The responses were integrated in time by a computer of average transients (CAT). Weiss and his colleagues hypothe sized that a negative pressure would Indicate an inward movement of the eardrum whereas a positive pressure change would Indicate an outward movement. From morphological-anatomical evidence, an inward movement of the eardrum could be associated with a contraction of the tensor tympani muscle whereas an outward displacement might indicate a contrac tion of the stapedius muscle. Results indicated that both muscles contributed to the acoustic reflex in most subjects. As the duration of the stimulus signal increased, with intensity held constant, the responses of the subjects varied. A typical response demonstrated a positIve-pressure change, whereas other subjects demonstrated a negative-pressure change. The latter responses are d ifficu lt to explain on the basis of only one middle-ear muscle responding as advocated by
Klocknoff (31, 32).
Holst, and others (21) reported several results concerning the movement of the eardrum after stimulating the middle-ear muscles by various procedures: (a) stimulation of the eye with a small blast of 20. air caused the eardrum to move inward; (b) blowing air against the opposite auricle caused the eardrum to move outward; and (c) acoustic stimulation (500 cps) of the opposite ear at an intensity of 127 dB
(re 0.0002 dyne/cm^) resulted in a biphasic movement of the eardrum, outward in itially followed by an inward movement. The results were obtained with a manometric system similar to the apparatus used by
Weiss and his co-workers.
U tiliz in g measurements of acoustic impedance and cochlear micro- phonic potentials, M iller (52) studied the movements of the tympanic membrane In cats and rabbits. He concluded that In contrast to the stapedius muscle, the tensor tympani moves the eardrum inward creating a negative pressure within the ear canal. In other instances the stapedius muscle created a negative pressure and, in combination, the two muscles also created a negatlve-pressure change. The combined e ffe c t of the m iddle-ear muscles caused more impedance change than did contraction of e ith e r muscle alone. M dller concluded th at even though the middle-ear muscles are anatomically antagonistic, they are probably synergistic in their physiological function of controlling the "mobil ity and transmission property" of the middle ear.
The follow ing explanation of Mundie (55) provides some resolution to the above contradictory findings:
( I) There is a complex relatio n sh ip between tensor tympani and stapedius muscles in which the muscles act In oppo s itio n . Tensor tympani draws the manubrium and attached tympanic membrane inward to tighten the ossicular chain against the head of the stapes which is "anchored" by the action of the stapedius muscle. (2) This combined action results In an Increase of elastance which is asymetrical. As sound pressure now drives the drum, an inward motion sees an elastance of the stapedius muscle and an outward motion sees elastance of tensor tympani* (3) A further res u lt of th is combined action o f the two muscles Is to alter the incudo-stapedial joint In such a manner as to change the mode of ro ta tio n of the stapes in the oval window (as described by B&cisy fo r loud sounds). This effectively "de-couples" the cochlea from the conductive mechan ism.
Central factors. Djupesland (13) reported that the impedance of the ear changes 40-450 msec before the onset of phonation and continues for as long as 300 msec after the cessation of phonation. Expectation of a loud noise (a toy pistol pointed at the opposite ear) caused contraction of both middle-ear muscles, suggesting central control of these muscles.
The influence of central factors on the middle-ear muscles also was demonstrated in a study by Fletcher and Rtopelle (21). They conditioned the acoustic reflex with a brief tone just prior to a rifle noise. This procedure decreased the temporary threshold shift as determined by audiometric procedures.
Summary: function of the middle-ear muscles. With this portion of the review of the literature, the anatonical identification and results relevant to the function of the middle-ear muscles have been described. The experimental results have demonstrated (a) the graded amplitude of the impedance changes and (b) the inverse relationship between the latency of Impedance change and the in te n s ity of the noise stimulus. Apparently the two muscles of the middle ear are in a constant state of activity, exerting a continual Influence on the transmission of sound energy via the middle-ear structures. 22.
Additionally, it has been pointed out the precise function of the
tensor tympani muscle is not c le a riy understood.
Measurement of acoustic impedance
Current procedures fo r the measurement of acoustic impedance are based on the p rin cip les used to measure e le c tr ic a l and mechanical impedances. The acoustic bridges used to obtain measures are either a mechanical-acoustical or an electro-acoustic apparatus.
Mechanical-acoustical impedance bridges. An acoustic bridge constructed s p e c ific a lly fo r acoustic impedance measurements of the human ear was developed by Metz (42). His device was based on the acoustic bridge of Schuster ( 67) which was designed to determine the acoustic properties of various materials. Metz utilized his acoustic bridge In the study of normal and pathological ears. He concluded that this instrument could be useful in the diagnosis of hearing
impairments, especially for the determination of a conductive hearing loss associated with otosclerosis. The Metz apparatus was not generally accepted by other experimenters, probably due to Its awkardness and the calculations that were essential in order to
interpret the data.
Zwislocki {85, 86) has described the development and uses of a mechanical-acoustical impedance bridge that is a refined version of the Metz device. This instrument, now commercially available (Grason
Stadler, Zwislocki Acoustic Bridge, Model 3)» is schematically represented In Figure 4. MONITOR Y-TUBE
MATCHING SPECULUM IMPEDANCE
srv^v ^vi I- - - J VAr-______
^ 3 X \ \ \ \ \ 5 X
TRANSDUCER
\
Figure 4. Schematic cross-section drawing of the Zwislocki Acoustic Bridge. The speculum inserts into the subject's ear. The transducer produces sound waves of opposite phase in tube A and tube B. The volume of the subject's ear canal is set at V i. The experimenter monitors the phase and amplitude relationship between tubes A and B white adjusting the matching impedance; Is resistance and V2 Is the compliance volume. See text for additional explanation. Ih
As described by Zwislocki (89) a symetrical electro-acoustic transducer is situated between two main tubes, A and B, having equal dimensions except for the variable impedance-matching section of tube B. The accurately measured volume of the s u b je c t's ear canal is added to volume (V|) of tube B. This adjustment cancels the effect of the ear-canal volume during the impedance measures. A pure tone between 125 cps and 1500 cps drives the transducer, esta b lis h in g a separate continual sound wave w ith in each of the two tubes. These two standing waves have the same amplitude and frequency, but are opposite in phase by 180 degrees only when the impedances w ith in the two tubes are identical. The experimenter accomplishes this relationship by adjusting the v a ria b le impedance matching section of tube B u n til the
Impedance o f a su b ject's e a r. The impedance e q u a lity (matching) can be detected by monitoring tubes A and B simultaneously until cancel lation Is obtained indicating the two sound pressures are of equal frequency and amplitude, but opposite in phase by 180 degrees. This
Is designated as a null p o in t.
Resultant measures obtained by adjusting the matching impedance of the bridge are compliance in equivalent volume ranging from .1 cc to a maximum of 5 cc, and arbitrary resistance units from 0 to 60.
Compliance can then be converted to acoustic reactance (ohms) and arbitrary resistance can be converted to acoustic resistance (ohms).
Investigations with the Zwislocki Acoustic Bridge have been reported by several authors. Zwislocki (89) described the Impedance 25.
measures obtained from normal subjects, o to s c le ro tic subjects, and a
subject with a prosthesis replacement for the stapes. Among other
things, he indicated that subjects could be differentiated best on the
basis of impedance measures a t lower frequencies^ (125 cps, 250 cps, and 500 cps).
Feldman (1 6, 17) advocated the routine use of impedance measures
in the diagnosis of hearing disorders. Figure 5 shows impedance measures that he reported fo r three individual subjects: one without an Incus, one w ith a normal middle e a r, and one w ith oto sclerosis. He stated that these were typical examples demonstrating that measures obtained from a normal middle ear usually are intermediate in magnitude to the two pathological types of measures. Feldman (17) also indicated th at the normal and otosclerosis d is trib u tio n s fo r compliance overlap minimally at 125 cps through 750 cps. He considered this overlapping to be nonsignificant (no statistical test used except median scores).
At 1000 cps the distributions were considered "too broad for diagnostic evaluation."
Da 11 os (11) as well as L illy and Shepard (36) employed the
Zwislocki apparatus in studying the acoustic reflex. The latter authors reported that the acoustic bridge yielded results similar to those
3 Several frequencies are often used when measurements of acoustic impedance are obtained. The test frequencies are usually in the range o f 100 cps to 2000 cps, however, measures obtained near the resonance of the middle ear (about 1*K)0 cps) are sometimes confounded. Some authors Indicate that the lower test frequencies are the most useful for the study of middle-ear functional differences. COMPLIANCE (IN CC OF EQUIVALENT AIR VOLUME) component of impedance, resistance, Is expressed in arbitrary units units arbitrary in expressed Is resistance, impedance,component of iue . oprtv ipdne esrs o oe a wtot n nu (——e one , ) e (o—o— Incus an without ear one impedance Comparativemeasures for 5. Figure o m! a (—* ), ad n er igoe a ooceoi (----- h imaginary The . ) (#------x volume of cc equivalent otosclerosis as in diagnosed expressed ear one and Is , Impedance, compliance, ) component • of (•—-*— ear norma! 2.0 3.0 4.0 0.2 0.9 3 0 5.0 0.5 0.8 Ofi 0.7 125 R QE C I CCE PR SECOND CYCLESFREQUENCY IN PER 250 0 70 I 750 500 k £ cc UJ CO (/> Ui z O < 0£ CD H cc CC V z H tn < 3 60 50 40 45 30 20 35 25-*- 125 250 500 750 750 500 250 125 RQ EC I CCE PR SECOND CYCLESFREQUENCY IN PER (17)* ?! air. h real The I k
1 . 5 k 27. obtained from an electro-acoustic bridge developed at Central Institute for the Deaf.
Tillman and others (80) studied the reliab ility of measures obtained with the Zwislocki bridge. Three experimenters measured ten normal-hearing subjects, and concluded that compllance measures were more reliable than resistance measures. In addition, they also cautioned that compliance values a t 1000 cps should be evaluated c a re fu lly due to the resonance of the middle-ear.
The reliability of measures obtained with the Zwislocki bridge in a "typical clinical situation" was reported by Nixon and Glorig (58).
They stated th a t impedance measures showed g reater v a r ia b ilit y as frequency increased. In addition to resonance of the ear, they a ttri buted this variability to the possibility of a "measurement artifact."
As a consequence, they excluded data obtained a t 1200 and 1500 cps from their data analysis because the variability seemed to make these particular data meaningless.
Using the Zw islocki bridge, Feldman (18) found the median com pliance measures of 11 ears that had the same type of prosthesis substituted for the stapes to be essentially equal to the mean compli ance measure obtained from 33 norm al-hearing subjects.
The discussion of impedance measurement of the ear now continues w ith a review of electo -aco usttc impedance bridges.
E lectro -aco u stic Impedance bridges. M ille r (**6) has described an electro-acoustic impedance bridge similar in principle to a mechanical-acoustic impedance bridge. Certain differences exist: (a) it 28.
can be firm ly secured to the head which allows the subject to move
without altering the placement of the bridge, and (b) the phase and
amplitude adjustments, essential for determining impedance, involve
electronic as compared to mechanical procedures. In two subsequent
reports (*f7» *t9) he furnished detailed descriptions of his apparatus
used in development of an electrical analog of the middle ear.
The bilateral, simultaneous responses of the middle-ear muscles
was reported by Holler in a comprehensive article in 1962 (50). Using
several types of acoustic stimuli at various intensity levels, he
demonstrated concisely that an electro-acoustic bridge was effective
in detecting bilateral impedances. In his most recent publication (52),
M iller adapted his apparatus to animal studies on the middle-ear muscles.
Another electro-acoustic bridge was developed by Terklldsen and
Nielsen (77)* They utilized their device in several diagnostic proce dures. This bridge y ield s re la tiv e measures since an average volume of
the ear canal is used rather than individually-measured volumes. This
Instrument uses a fixed frequency of 220 cps as the c a rrie r frequency
since these investigators are of the opinion that only one frequency is needed to obtain adequate measures. In another article (78) , Terkildsen
reported that compliance measures between .05 and .60 cc indicate high
impedance such as may be found in persons w ith otosclerosis. Normal measures were about .65 cc and low Impedance was indicated by volumes between 1.05 and 3.5+ cc. 2 9
Otosclerosis and Stapedectomy
In this section a brief description of otosclerosis Is presented.
The stapedectomy procedure fo r improvement o f hearing associated w ith otosclerosis is also discussed, Including some information concerning the parameters of the replacement prostheses.
Goodhill (24) presented the following description concerning otosclerosis.
Otosclerosis, the chief cause of stapes ankylosis, Is probably not one specific disease; it is, more 1 ikely a sclerotic process in the otic capsule which may be the sequel of any of a number of different basic diseases. It is a disease which may occur anywhere within the otic capsule, with any degree of invasion of the lab yrin th , its windows, and its appendages.
The most significant pathologic lesion is the mechani cal stiffening and ultimate fixation of the stapedio- vestibular articulation.
Newby (57) reported that the most common audiolog leal sign associated with otosclerosis is a conductive hearing loss without obvious physical causes, that is , the eardrum usually appears normal and th e re Is o fte n no knowledge of middle-ear disease that might account fo r th e hearing impai rment.
Metz (42) was perhaps the f i r s t experimenter to re p o rt high acoustic impedance values associated with otosclerosis. Zwislocki (86) and Feldman (17) have also reported high-impedance values in a person with otosclerosis that was confirmed at surgery (see Figure 5) • Other reports (29, 3 1 , 81) have indicated that the absence of a stapedius reflex or the presence of only a tensor tympani response are indications of otosclerosis. Goodhill (24) reported that in spite of numerous 30. diagnostic signs that seem to indicate otosclerosis, the final confir mation cannot be made until surgery reveals the otosclerotic lesion.
The history of experimental techniques and procedures used to alleviate hearing loss due to otosclerosis includes some that have been successful and others that have been of little or no avail (23)* Among others, the procedure now termed stapedectomy was developed by Shea ( 69) wherein the stapes is replaced with a short polyethylene tube attached to a vein graft covering the fenestrated oval window. His procedure has been accepted and modified by numerous surgeons; only a few of the modifications will be presented here.
Usually the entire stapes, including all fragments of the foot plate, is removed from the oval window and replaced with a prosthesis.
Some examples of prosthetic devices are shown in Figure 6: (a) the polyethelene tube firs t described by Shea ( 69), (b) a modified Teflon piston which was originally described by Shea (70), and (c) a wire-
Silastic prosthesis (60) which is a modification of the wire prosthesis described by Schuknecht (66). A stapes drawn to scale is also included fo r comparison. The dimensions indicated in Figure 6 are approximate values since they may be modified during surgery.
Several other prostheses have been developed. For example, an oval-Teflon piston, in contrast to the round one shown in Figure 6, approximates the size of the footplate of the stapes. The wire prosthesis group also includes (a) a wire with a fat graft, (b) a wire with a Gel foam graft, and (c) a wire with an attached stainless-steel piston. T) E 6 i O r
5mm STAPES WIRE-TEFLON 2mm
£ E ■1) 10 5mm 5mm POLYETHELENE WIRE-SILASTIC TUBE - VEIN 2mm
Figure 6. Schematic drawing of the stapes and three replacement prostheses. The indicated — dimensions are approximate. Additional description Is Included in the text. 32.
An additional procedure described by Goodhill (24) Is called
the interposition or partial stapedectomy. In this operation, the
footplate is fractured free from the otosclerotic growth by the use of picks while preserving, if possible, the stapedius tendon. In some
instances the stapes Is temporally removed and a vein or muscle graft
is placed beneath the footplate.
The foregoing discussion points out that there are a number of techniques c u rre n tly employed fo r the replacement of the stapes.
Certain investigators have attempted to resolve some of the parameters concerning the substitute stapes. Anderson and others (6) studied the effect of mass** as a variable of the prosthesis in prepared human- temporal -bone specimens. They removed the stapes except for the footplate and replaced It In turn with each of three similar prostheses.
One of the substitutes was a Shea polyethelyne tube weighting 1.9 mg.
The other two, identical in shape and size with the tube prosthesis,
included a steel prosthesis weighing 13 mg and a gold prosthesis weighing 62 mg. The experimenters measured the transmission charac teristics of each replacement and found that the mass did not have a significant effect on sound transmission through the middle ear. In an earlier study, Anderson and others (5) determined that the positioning o f the prosthesis was more c r it ic a l than the mass.
** The weight of the human stapes ranges from 2.0 to 4.3 mg (75). 33.
A lle n and others (1) compared the e ffic ie n c y of two s p e c ific prostheses by measuring cochlear microphonic responses. They removed the stapes from cats and the replacement was either a w ire-fat prosthesis or one made of wire-Teflon. Their results indicated a decrease in the microphonic response for both substitutes, suggesting a minor conductive hearing loss. The wire-fat prosthesis resulted in a loss of sensi tivity that increased in the higher frequencies whereas the wlre-Teflon prosthesis resulted in a flat loss of microphonic responses that was greater in the low frequencies and less than the wire-fat for the higher frequencies.
Conclusions from the foregoing experimental studies should be made with caution. The post-operative period in humans is critical and hearing should be checked p e rio d ic a lly as advocated by Moncur and
Goodhill (53). They indicated that a "near maximum" gain In hearing occurred within the firs t 30 days after surgery, a finding confirmed by Sooy and others (7 ^ ).
Some w rite rs have measured acoustic impedance follow ing stapedec tomy. Terkildsen (73) indicated that compliance increased after surgery for 12 persons studied. He stated that "impedance determi nations are of 1ittle value for the purpose of varlfying the results of operations for otosclerosis." On the other hand, Zwislocki (91) has stated th at "absolute Impedance measurements can help in evaluating surgical technics." 34.
Feldman (1 7 )* In describing the increase In compliance In a
group of stapedectomized persons, Indicated that these values do not
approach normal. He also reported that it was not possible to obtain
compliance measures a t 750 cps and 1000 cps, in d icatin g a lack of
stiffness in the middle-ear structures. These results are difficult
to interpret since the number of subjects and measures of variability
were not indicated.
A unique procedure for determining hearing Improvement resulting
from middle-ear surgery Is described by Goodhill (23, 24). This
procedure, called the nomograph technique, utilizes pure-tone a lr-
conduction thresholds before, during, and after surgery on a compara
tive basis. The most important step occurs immediately after the
manipulations and/or the replacement prosthesis Is in place. The
threshold measures obtained at this point enable the surgeon to make
a p red ictio n regarding the amount o f improved air-conductIon hearing
that may be anticipated after surgery.
Newby (57) stated that stapedectomy procedures are considered
successful If the "air-conductIon hearing can be restored to within
10 dB of the bone-conduction hearing." However, even when results
are "successful11 other problems may be manifested. Moncur and Good
h ill (53) reported a reduction In discrimination scores among a group
of 75 persons after stapedectomy as compared with their discrimination
ability before surgery. Helnick (41) described a change in the judgment of subjects with regard to their own phonation level.
Lawrence (34) indicated that middle-ear surgery appears to create problems that cannot be assessed by routine pure-tone audiometry* He feels that removal of the Influence of the middle-ear muscles can result in abnormal sensitivity to intense sounds. More recently*
Lawrence (35) indicated that careful experimentation should be con ducted to determine the function of the middle-ear when It has been altered by surgical intervention.
Summary
In this chapter a review of the literature concerning the function of the middle ear as welt as the two middle-ear muscles was presented, in addition the theory and applications of acoustlc- impedance measurements were described. A b rie f description of oto scle rosis and stapedectomy surgery was also included. The following chapter describes the procedures and instrumentation employed in the present study. CHAPTER t i l
INSTRUMENTATION AND PROCEDURES
The prupose of this chapter is to describe the criteria for selecting subjects, and the instrumentation and procedures that were used to obtain the measurements of acoustic impedance, hearing sensitivity, and the latency of an acoustic reflex.
Selection of subjects
Forty adults, 22 males and 18 females, ranging in age from
18 to 62 years, w ith a mean age of 30 years and a standard deviation of ten years served as the normal-hearing subjects for this study.
Thirty-two adults, ten males and 22 females, ranging in age from
29 to 77 years, with a mean age of 50 years and a standard deviation of
12 years served as stapedectomized subjects. Since eight of these subjects had been stapedectomized in both ears, the total number of measured ears was 40. In accordance w ith the descriptions In Chapter
II, ten of these persons had a wire-Teflon^ prosthesis, ten had a polyethylene-vein prosthesis, and ten had a wire-Silastic prosthesis.
The remaining ten stapedectomized subjects had prostheses of several
5 Teflon, Silastic, and Gelfoam are commercial synthetic m aterials which are sometimes used in various surgical procedures.
36. 37. types: two w ire-T eflo n (oval p is to n ), two w ir e - fa t , two po lyeth ylene- vein, one wlre-Gelfoam, and three partial stapedectomies.
Sixteen adults, six males and ten females, ranging In age from
18 to 67 years, with a mean age of 46 and a standard deviation of 13 years served as the otosclerotic subjects. Since four of these
Individuals had bilateral otosclerosis at the time the measures were obtained, the total number of otosclerotic ears that were measured was 20.
Instrumentation
Assessment of hearing sensitivity. An audiometer (Beltone,
Model 10-C) was used to determine the relative difference between air-conductlon and bone-conduction sensitivity for all subjects. The audiometer was calibrated to the 1951 ASA standards (4) prior to testing. When bone-conduction thresholds were determined for the normal-hearing subjects, a white-noise masking signal was presented to the opposite ear to prevent lateralization of the test signal to the non-test ear.
Acoustic-impedance measures. The acoustic Impedance measures for the 40 normal-hearing subjects were determined in a sound-treated room having an average ambient noise level of 45 dB SPL. The instrum entation used fo r the impedance measures ts illu s tra te d in
Figure 7* An audio-signal generator (Hewlett Packard, Model 205-AG) supplied a sinusoidal signal to the acoustic bridge at a sensation level of 55 dB (above the threshold of each subject). A monitoring SIGNAL GENERATOR
ZWISLOCKI ACOUSTIC BRIDGE
SUBJECT
Figure 7* Instrum entation fo r the measurement of acoustic impedance. 39. stethescope, as shown photographically in Figure 8, was used to aid In matching the impedance of the acoustic bridge to the Impedance of the subject's ear.
Figure 8. The Zwislocki Acoustic Bridge with the monitoring stethescope.
Contralateral acoustic reflex. The instrumentation used to measure acoustic impedance was also used fo r the detection of the acoustic reflex with certain exceptions as shown in Figure 9* The stethescope monitoring tube was replaced by an Intensity-detectIon and recording network. In addition, a series of instruments was used to generate and present a white-noise signal to the contra lateral ear of each subject at 88 dB SPL. POWER SUPPLY WAVEFORM GENERATOR X PULSE GENERATOR SIGNAL RUBBER GENERATOR PULSE TUBE L POWER AMPLIFIER BAND | GENERATOR)- ! SUPPLYT REJECTION ^ FILTER-i—J WHITE-NOISg ELECTRONIC MICROPHONE GENERATOR SWITCH I LEVEL COMBINED RECQRDE AMPLIFIER, NOISE STIMULUS FILTER a EARPHONE STIMULUS VOLTMETER RECORD - PEN IMPEDANCE MATCHING RELAY TRANSFORMER I POWER SUPPLY
Figure 9. Instrumentation for the measurement of an acoustic reflex shown schematically 41
The intensity-monitoring and recording network consisted of
several components. A condenser microphone (Altec, Model 210)
with an associated power supply (Altec, Model 525-A) was coupled to
the output of the Y-tube of the acoustic bridge of a 12-Inch rubber
tube. The microphone output was amplified (Hewlett Packard, Model
450-A) and fed to a band-rejection filte r (Krohn-Hite, Model 360-A)
to attenuate the low-frequency noise. The signal was then amplified
and selectively filtered (Bruel and Kjaer, Type 2105) at the carrier
frequency of the acoustic bridge, 500 cps. The signal could be
visually monitored on a voltmeter and/or graphically recorded on a
level recorder (Bruel and Kjaer, Type 2304) at a paper-movement rate of 30 mm per second.
The white-noise signal (Grason-Stadler, Model 455-B) used as a
stimulus for the acoustic reflex was fed to an electronic switch
(Grason-Stadler, Model 829-0) controlled by pulsed voltages from two pulse generators (Tektronix, Types 161 and 163). The pulse generators were triggered at selected voltage levels by the output of a sawtooth waveform generator (Tektronix, Type 162). The line of equipment was programmed and calibrated to produce three-second bursts of white- noise having rise and decay times of five msec with an interval of seven seconds between bursts. The w hite-n oise signals were passed through an impedance-matching transformer to the stimulus earphone
(Beltone, M-3), which delivered the noise bursts to the ear at a level of 88 dB SPL via an insert with a tight-fitting sealing tip. 42
To record the onset and the termination of each noise stimulus,
the on and off pulses used to trigger the electronic switch were
recorded on the level recorder by a solenoid-marking stylus.
Calibratlon of the reflex recording system. As suggested by
Simmons (71), the time delays Inherent to the Instrumentation were
measured to determine more accurately the latency of the acoustic
reflex as indicated by a change of impedance.
One delay was determined by displaying the onset of the pulse
from the pulse generator and the onset of the signal at the input to
the solenoid-marking pen on two beams of an oscilloscope (Tektronix,
Type 504). By this means, a delay of approximately eight msec was
noted. By the same procedure, the delay between the onset of the
pulse generator and the peak energy of the noise stimulus was
determined to be approximately 20 msec as illustrated In Figure 10.
The delay of the stim ulus-record pen (see Figure 9) was determined with the oscilloscope and a photoelectric transducer. One beam of the
oscilloscope was used to display the onset of the pulsed voltage from
the pulse generator and the second beam to display the onset of the
output of the photoelectric transducer arranged to respond to an
increase in light intensity coincident with movement of the marking
pen. A delay of 25 msec was found to exist between the pulsed
voltage and the movement of the stimulus-marking pen. The delay of
the response pen was measured as 15 msec by a s im ila r procedure.
After determining each of these delays, a correction factor of 20 msec was established based on the delay of the stimulus pen (five msec) Figure 10. Calibration of the noise stimulus as viewed on an oscilloscope screen; time is represented horizontally, five msec per square, and relative Intensity is represented vertically. The lower trace (B) indicates the onset of the pulsed voltage to the electronic switch where the voltage increases abruptly for about eight msec. The upper trace (A) indicates the onset of the noise stimulus approximately 20 msec after the onset of the pulsed voltage of trace B. plus the response pen delay (15 msec). Figure 11 shows these delays schematically. The correction factor of 20 msec was then subtracted from the response times of the acoustic reflexes which are presented
in Chapter IV.
Procedures
Measurement of normal- hearIno s e n s itiv ity . The thresholds of hearing sensitivity were determined for 15 female and 15 male adults tj- pulse voltage uon,( t2- pulse arrives at S pen t 3- peak energy of S noise tif- S pen marks paper t j - response onset tfc- R pen marks msec msec
time In msec *
acoustic 15 ref 1 ex msec pen - h
Figure 11. A schematic diagram showing the analysis of Instrumentation time delays for the measurement of an acoustic re fle x as detected by a change of acoustic impedance. The upper line represents the stimulus pen circuit (see Figure 9) and the lower line represents the response pen. 45. in a randomly selected ear at the frequencies 250 cps, 500 cps, 750 cps, and 1000 cps. Measures were obtained for a 1r-conducted and bone- conducted stimuli. The bone-conductIon thresholds were obtained using
78 dB SPL of white noise In the opposite ear to prevent lateralization of the signal through the skull. Threshold values were checked by attenuating the level of the masking signal to determine that the level did not reduce the sensitivity in the measured ear.
Roach and Carhart (64) have suggested that the procedure of using normal-hearing subjects can be used for the calibration of a bone-conduction transducer. They report th at such co rrectio n values, obtained by subtracting the afr-conduction threshold from the bone- conduction threshold, are equivalent to correction values obtained from persons with a sensorineural hearing loss, a procedure suggested by Newby (5 7 ).
Based on the obtained correction values for bone-conduction sensitivity, a relative difference could be obtained for all subjects.
For normal-hearing subjects, this value was approximately 0 dB, whereas the value for persons with a conductive hearing loss would be greater than 0 dB. For subjects with a "pure" sensor[neural- hearing loss, the relative difference should also be near 0 dB.
Measurement of hearing fo r o to s c le ro tic and stapedectomized subjects. It should be mentioned at this point that not all of these subjects could be tested in the same sound-treated room in which all of the normal-hearing subjects were tested since many of the former subjects were private patients of otologists. This factor made it 46 .
necessary to test some persons tn locations other than the sound-
treated room. Being aware that such measures are less valid than
those obtained in a quieter environment, care was taken to control
the ambient-noise levels.
The subjects with otosclerosis and stapedectomy were tested by the same procedure that was used fo r the normal subjects. Bone- conduct ion and air-conduction threshold values were obtained for the frequencies 250 cps, 500 cps, 750 cps, and 1000 cps. These values were recorded and the correction factors determined from the normal subjects were applied to these data. The resultant scores obtained were relative differences in decibels between air-conduction and bone-conduction sensitivity to sinusoidal signals.
Measurement of acoustic impedance. The procedure to be described was utilized for all subjects with an exception that w ill be explained at the end of this section.
Before any measures were obtained a ll cerumen was removed from each subject's ear canal and the ear-drum was inspected to make certain that there were no perforations.
The subject's head was positioned on a firm pillow with the ear th at was to be measured d ire c tin g upward. A p la s tic sealing tip of an appropriate size (either small, medium, or large) was fitted to the ear speculum and coated with Vaseline to assure an air-tight seal.
The speculum was then placed in the subject's ear and directed at the ear drum as illu s tra te d in Figure 12 fo r the measurement of ear canal volume pictured in Figure 13* Figure 12* Placement of the Figure 13. Measuring of the ear speculum fo r the measure ear canal volume prior to the ment of acoustic impedance. measurement of acoustic impedance.
Zwislocki (87) stated th a t the volume o f the ear canal must be
determined accurately since the value of the volume Is essential for
the calc u la tio n of impedance. Figure 13 illu s tr a te s the manner by
which the ear canal volume was assessed with 70% ethyl alcohol
introduced via a 1 cc syringe calibrated in .01 cc increments. The
ear canal was considered full when the alcohol just reached the tip of
the speculum. Good lighting was essential so a ten inch head mirror and lamp were u t iliz e d fo r th is measurement. The volume was then
recorded and all alcohol was removed from the ear canal.
The measured volume of the ear canal was set on the acoustic bridge as indicated in the instruction manual for this instrument (24).
The ear speculum was inserted in the same p o sitio n th a t was used fo r
the volume measurement.
The acoustic bridge was next inserted into the speculum, in a manner not to d is tu rb its p o sitio n as shown in Figure l^t. The Figure 1**. The Zwislocki Acoustic Bridge in position for measures of acoustic Impedance. acoustic impedance measurements were determined a t the frequencies of
250, 500, 750, and 1000 cps by the experimenter. This was accomplished by aurally monitoring the effect of adjusting the phase and amplitude of the signal in the matching-*impedance section of the acoustic bridge in comparison with the phase and amplitude of the signal in the tubular chamber to the ear of the subject. When the two slgnais were out of phase by 180 degrees, and when the amplitudes of the signals were equated, a null was detected by the experimenter. The adjusted volume and arbitrary resistance values obtained with the acoustic bridge at the null point were then recorded. 49.
A fte r the above measures were obtained a t the four d iffe r e n t
frequencies, the bridge was removed from the subject's ear* The ear
canal volume was then re-measured for only the 40 norma I-hearing
subjects. These measures were obtained in order to determine the
reliability of this measurement.
An exception to the above procedures was as follows: when
impedance of a subject was measured in a location other than in the
sound-treated room, the audio-signal generator (Hewlett-Packard
205-AG) was replaced by the audiometer (Beltone 10-C) used for the hearing measurements. Satisfactory agreement between these two
similar procedures was obtained In a pilot study which is described
in Appendix A of this study.
Measurement of the acoustic reflex. A change in acoustic
impedance was determined fo r ten of the 1*0 normal-hearing sub jects, fiv e males and fiv e females. This change in acoustic impedance
resulted from a white-noise stimulus in the opposite ear.
Each subject was positioned on a table with his head on a firm pillow and turned so that a randomly-selected ear could be prepared for the reflex measure. The insert earphone was placed in the opposite ear for presentation of the white-noise stimuli.
The canal of the te s t ear was examined and its volume measured as previously described. After removal of the alcohol, the speculum was replaced and held firmly in position by the supporting mechanism
illu s tra te d In Figure 15* The bridge was placed In the speculum and a null was obtained at the frequency of 500 cps. The aural-monltorIng Figure 15* The apparatus for supporting the acoustic bridge during recording of the acoustic reflex response. tube was replaced with a 12" rubber tube connected to the intensity- recording apparatus. The experimenter then checked the obtained null point with the volt meter to make certain that the impedance did not change as the result of movement on the part of the subject.
Six white-noise stimuli lasting three seconds were presented with an interval of seven seconds between successive noise bursts.
The impedance of the opposite ear was recorded on a level recorder
(B ruel-K jaer, Model 230*0 at a paper speed of 30 mm second. After the last noise burst had ceased, the ten normal-hearing subjects were prepared in the same manner for measurement of their opposite ear. The experimental procedures employed for the ten normal-hearing subjects were followed in the same manner for the test ears of the ten stapedectomized subjects. The noise-stimulus ear had normal hearing sensitivity as defined in Chapter I.
Summary
In this chapter the criteria for selecting subjects, the instrumentation, and the procedures were described. The explanation of the instrumentation included a description of calibration procedures for measurement of the acoustic reflex. CHAPTER IV
RESULTS AND DISCUSSION
The purpose of this study was to investigate certain parameters
of the function of the middle ear through measures of acoustic
impedance and hearing sensitivity. Forty subjects with normal-hearing
sensitivity, **0 with stapedectomy, and 20 with otosclerosis served as experimental subjects to determine whether measures of acoustic
impedance could be used to differentiate these groups. The relation ship between the re la tiv e air-bone gap and acoustic impedance was also
investigated for all subjects. In addition, the latency of the acoustic reflex, as determined by an impedance change, was studied for 10 subjects with norma I-hearing sensitivity and 10 stapedectomized subjects with normal-hearing sensitivity in the contralateral ear.
Three null hypotheses were formulated and tested. The results and discussion pertaining to each hypothesis will be presented In this chapter.
Hvpothesis I : Acoustic Impedance Measures. There is no difference between the acoustic-impedance measures fo r pairs of groups of subjects with (a) normal-hearing sensitivity and otosclerosis, (b) normal- hearing sensitivity and stapedectomy, and (c) otosclerosis and stapedectomy.
52. The measures of compliance In equivalent-air volume (cc) and
the arbitrary resistance units were converted to acoustic ohms (25).
Compliance scores were transformed Into ohms with the formula:
x = M3 x Ip6 2 trf x v2 where (X) represents reactance in acoustic ohms, (f) the measurement frequency, and (V2) the equivalent volume obtained for the acoustic bridge. The numerator is a constant conversion factor for the
Zwislocki Acoustic Bridge. The relationship between equivalent volume and acoustic reactance is shown graphically in Figure 16. Reactance units can be interpreted from the graph; however, the formula is more precise.
The measures of arbitrary units of resistance were converted to acoustic resistance with a c a lib ra tio n graph (25) that Is reproduced
in Figure 17. The acoustic resistance and acoustic reactance values were then combined by vector analysis of the determination of total
impedance as described in the firs t chapter. These data (compliance, arbitrary resistance, acoustic reactance, acoustic resistance, and to ta l impedance) are lis te d in Appendixes B, C. and D.
The data, as listed in the appendixes, were reduced statistically
(19) by determining the median, mean, and standard deviation of the values for each group of subjects at the four test frequencies, 250,
500, 750, and 1000 cps. The results of this analysis are presented in Table 1. It should be noted that the number of subjects (N) varies: the values of those subjects whose compliance exceeded the lim it
(5 cc) of the acoustic bridge was not included. 1K
u O z < f- o < Ui ft
100.
VOLUME (cc)
Figure 16. A graph showing the relationship between the equivalent volume measures obtained with the Zw!slock I Acoustic Bridge and reactive acoustic Impedance In acoustic ohms. «
I 4-i.
1000
to , i 4_ 3o 2 — s o o < 100. RESISTANCE (arbitrary unita) Figure 17. A graph showing the relationship between the arbitrary resistance measurements obtained w ith the Zw lslocki Acoustic Bridge and re s is tiv e Impedance in acoustic ohms. Table 1. A listing of means, standard deviations, medians and the respective N associated with each value determined from the measures of impedance, compliance, and resistance for a ll subjects. Com pliance values that exceeded the lim it (fiv e cc) of the acoustic bridge were excluded from the mean and standard deviation scores as indicated by the differen t values of N within groups. NORMALS STAPEDECTOMY OTOSCLEROSIS Mean N s.d. Med Ian N Mean N s.d. Median N Mean N s.d. Med i an N Ifl^pedance 250 cps 1939 40 182 1837 40 1287 40 800 879 40 3034 20 232 2298 20 500 cps 838 40 102 817 40 443 39 318 344 40 1411 20 201 1067 20 750 cps 530 40 63 455 40 408 22 287 162 40 760 18 450 506 20 1000 cps 413 38 170 355 40 400 14 171 200 40 432 18 282 335 20 Conpllance 250 cps .53 40 .15 .52 40 1.06 40 .55 1.07 40 .48 20 .34 .42 20 500 cps .69 40 .22 .68 40 1.87 39 1.31 1.50 40 .56 20 .40 .45 20 750 cps 1.07 40 .57 .85 40 2.07 22 1.55 4.80 40 .86 18 .83 .60 20 1000 cps 1.45 38 .75 1.61 40 2.00 14 1.60 5+ 40 1.11 18 .93 .78 20 Resistance 250 cps 23 40 2.34 23 40 30 40 5.79 30 40 24 20 5.36 25 20 500 cps 25 40 2.31 24 40 32 39 6.61 32 40 27 20 5.55 27 20 750 cps 27 40 3.51 27 40 31 22 5.19 30 40 30 18 5.33 30 20 1000 cps 27 38 3.10 27 40 27 14 3.82 27 40 32 18 5.77 34 20 \n 57* The mean and median scores of to ta l impedance as lis te d In Table 1 show decreasing values with increased frequency for ail three groups* This finding indicates that impedance decreases due to the acoustic properties of the middle ear. The standard deviations of the mean total impedance scores demonstrates the least amount of variability among the normal group* whereas the stapedectomized and the otosclerotic groups showed the most variability and an Intermediate degree of variability respectively. The mean and median values for equivalent compliance and arbitrary resistance for the three groups* as listed in Table 1* increase with frequency except for the resistance values for the stapedectomized group. In this instance* the mean resistance value is at a maximum of 32 fo r 500 cps* decreasing to 30 at 750 cps and to 27 at 1000 cps. In spite of this exception* arbitrary resistance seems to be more independent of the four frequencies tested than does equivalent compliance. These findings are in agreement with the definition and description of acoustic impedance as presented In the first chapter. The median scores of total impedance fo r the three groups are shown graphically in Figure 18. This figure demonstrates that the obtained values of the normal subjects fall between the other two groups. It also seems that the median values showed differences between the stapedectomized group and the other two groups. This differentiation is more apparent than the separation between the normal and otosclerotic groups. 58. 5K 1 K !i 100 250 500 750 1K FREQUENCY (cps) Figure 18. Median scores of to ta l Impedance from Table 1 fo r the normal-hearlog sensitivity subjects (n ), stapedectomized subjects (s) , and the otosclerotic subjects (o) are shown graphically as a function of the four test frequencies. 59. The mean scores of to ta l Impedance w ith some of the standard deviation scores are presented in graphic form in Figure 19. Again the values fo r the normal subjects f a l l between the other two groups; however, In this instance there appears to be better differentiation between the groups as compared to the median scores p lo tte d in the previous figure. This differentiation is most apparent at 500 cps. The median scores for equivalent compliance and arbitrary resistance are shown graphically in Figure 20. The compliance values for the normal subjects fall between the other two groups, however, the resistance values are not as clearly differentiated. In this instance the median scores for the otosclerotic subjects are inter mediate to the other two groups at 250 and 500 cps. At 750 cps and 1000 cps, the p attern is changed by the decreasing values of resistance for the stapedectomized group. These decreasing values may be an artifact resulting from the use of resistance values when precise compliance values could not be obtained. The mean scores of equivalent compliance and arbitrary resistance, as shown in Figure 21, indicate the intermediate positioning of values for the normal group and an overlapping of the distributions; the latter is Indicated by the standard deviations of the mean scores for the normal group. Although not shown in Figure 21 , the standard deviation values for the other two groups serve to substantiate the factor of overlap. Based on the preceding graphic representations of the data, there appears to be a distribution overlapping between measures of compliance, 60 5K in 1K E UJ <_> Z < Q UJ 0_ s 100 500 1 K250 FREQUENCY(cps) Figure 19. Mean scores of total impedance from Table 1 for the normal- hearing sensitivity subjects (n) , stapedectomized subjects (s) , and otosclerotic subjects (o) are shown as a function of the four test frequencies. Some standard deviation scores are Indicated by brackets. 5 0 40 g 10 3 * 2.0 < 4* 3 > 1.0 2 5 OS 0.8 & 07 o '<* * 0 5 “ 0 .4 UJ 4 0 o < 0 .3 D a s o 02 5 0 125 250 500 750 I k 125 2 5 0 5 0 0 7 5 0 I k 1.5k FREQUENCY IN CYCLES PER SECOND FREQUENCY IN CYCLES PER SECOND Figure 20. Hedjan scores of compliance and resistance from Table 1 for the normal hearlng- sen sitlvity subjects (n ). stapedectomized subjects ( s ) , and otosclerotic subjects (o) are shown graphically as a function of the four test frequencies. 50 4 0 § 3 0 2 0 20 z D > CC < 05 a. 0.6 t m 3 0 0.7 o: 0£ < 0 5 u 0 4 o z 4 0 £ (A (A UJ (E 02 50 125 250 500 750 I k 1.5k 125 250 500 750 IK FREQUENCY ti C Y a E S PER SECOND FREQUENCY IN C Y a E S PER SECOND Figure 21. IfeUl scores of compliance and resistance from Table 1 for the normal heartng- sensitlvlty subjects (o ), stapedectomized subjects (s ), and otosclerotic subjects (o) are shown graphically as a function of the four test frequencies. The standard deviations of the mean scores for the normal subjects are indicated by the brackets. 63 resistance and to ta l impedance* This fin din g is more apparent between the o to s c le ro tic and normal subjects than i t is fo r normal and stapedectomized subjects, and stapedectomized and otosclerotic subjects. The best differentiating measure under the conditions of this study appears to have been the to ta l impedance a t 500 cps. In order to determine whether there were significant differences between the mean values just described some of the data for total impedance, compliance, and resistance were statistically analyzed by used t,-tests for unrelated means (19). Values of compliance and resistance at 750 and 1000 cps were not analyzed with t.-tests due to the diminished number of scores and increased variability. These analyses are summarized in Tables 2 - k. The t,-values listed In Table 2 Indicate the following differences between mean scores fo r the various groups. The normal and stapedecto mized groups were differentiated for compl lance on the basis of t,- values obtained at 250 cps (_t observed ■ 5.78> £ .001 “ 3.^35, df = 78), and at 500 cps (t observed * 5.62> t >0Ql - 3.^35, df « 77). Mean compliance values for the stapedectomized and otosclerotic groups were differentiated on the basis jt-scores obtained at 250 cps observed " ‘*•*'‘>1 .00! " 3-'*76' df " 58) - and at 500 CPS observe<)- 4.2if>Jt “ 3 .^ 76, df » 5 7 ). The normal and o to s c le ro tic groups could not be differentiated on the basis of the mean compliance measures a t 250 or 500 cps. No attempt was made to determine d if f e r ences between the mean compliance measures for any of the groups at 750 or 1000 cps due to the diminished number of scores and the Increased variability indicated by the standard deviation values. 64. Table 2. Values associated with _t-tests showing the differences between the comparisons of mean measures of equivalent compliance volume (cc) for normal hearing subjects, stapedectomized subjects, and otosclerotic subjects. The number of subjects in each group is indicated by the numerals in parentheses. 250 cps 500 cps Normals vs. ( 4 0 , 4 0 ) (4 0 , 39) Stapedectom i zed t *» 5 . 7 8 t = 5.62 d f ** 78 d f * 77 p < .0 0 1 p <.001 Normals vs. ( 4 0 , 2 0 ) (4 0 , 20) Otosclerotic t = 0 . 7 7 t = 1.54 d f = 5 8 d f ** 58 P < * 5 0 • 20> p> .10 Stapedectomized vs ( 4 0 , 2 0 ) (3 9 . 20) Otosclerot ic t - 4 . 2 4 t = 4.34 df - 58 df ■ 57 p < .001 p < .001 65. The t,-values listed In Table 3 indicate differences between the mean arbitrary resistance scores for the groups. The mean resistance values fo r the normal and stapedectomized groups were found to be d iffe r e n t on the basis of _t-scores obtained at 250 cps (t0|>served ~ 6,88 >t, ^qqj = 3.^35, df B 76) and 500 cps (^observed 0 6.57^ t, ^qq]~ 3.^35, df * 77). Mean resistance values for the stapedectomized and otosclerotic groups were shown to differ on the basis of obtained ^-values at 250 cps ^observed “ 3.79> t #00l » 3.W , df - 58) and 500 cps = 3.06>it *= 2.663, df « 57). These differences tended to be less significant for the latter pair of group comparisons as was the case for the mean compliance values. Again the values at 750 and 1000 cps were not compared because of the diminished number of scores obtained and increased variability at these frequencies. In Table b, the .t-values fo r mean to ta l - impedance scores are listed for each of the four test frequencies. In this instance the mean scores obtained at 750 and 1000 cps were compared to demonstrate the effect of using the decreased number of variant scores In this type of analysis, a procedure that can be viewed as violating the assump tions underlying this test (19). The t,-values 1 isted in Table b indicate certain significant differences between the mean total impedances for the three groups. The mean scores for stapedectomized and normal groups were found to be different at 250 cps (t0j,serve<| “ 3«48> t, Q01 - 3.^76, df » 78) and 500 cps (tobserved = 6.20>t, 00, - 3.576, df - 77). The t value fo r 750 cps indicated less difference (iQbserygd " |q “ 1 * 6 7• df = 60) 6 6 . Table 3. Values associated with t,-tests showing the differences between the comparisons of mean measures of arbitrary resistance for the normal hearing subjects, stapedectomized subjects, and otosclerotic subjects. The number of subjects in each group is indicated by the numerals in parentheses. 250 cps 500 cps Normals vs. (40, 40) (4 0 , 39) Stapedectomized t * 6.88 t “ 6.57 df - 78 df - 77 p < . 001 p < .0 0 1 Normals vs. (4 0 , 20) (40, 20) Otosclerotic t * 0.91 t = 1.95 df » 58 df *= 58 .40> p> .30 .10>p> Stapedectomized vs. (4 0 , 20) (3 9 , 20) Otosclerot1c t = 3.79 t * 3.06 df «* 58 df - 57 p < .0 0 l p < .01 67 Table 4. Values associated with t^-tests showing the differences between the comparisons of mean measures of to ta l impedance (ohms) for normal hearing subjects, stapedectomized subjects, and oto s c le ro tic subjects. The number of subjects in each group Is indicated by the numerals in parentheses. 250 cps 500 cps 750 cps 1000 cps Normals vs. (40, 40) (40, 39) (40, 22) (38, 14) Stapedectomized t = 3.48 t = 6.20 t * 1.92 t = 0.24 df = 78 df = 77 df = 60 df = 50 PC.001 p <.001 .1 0 > p > .0 5 n.s. Normals vs. (40 , 20) (40, 20) (40, 18) (38, 18) Otosclerot ic t * 2.72 t = 2.86 t * 2.64 t * 0.31 df = 58 df » 58 df = 56 df => 54 PC.01 p< .01 .05>p > .01 n.s. Stapedectomized vs. (40, 20) (39, 20) (22, 18) (14, 18) Otosclerotic t = 3.91 t * 4.68 t * 2.89 t = 0.36 df * 58 df = 57 df = 38 df » 30 p < .001 p< .001 P < .01 n.s. 68. and no statistical difference at 1000 cps (t . . = 0.24 The mean Impedance scores were d iffe re n tia te d on the basis of the ^-scores listed in Table 4 for the normal and otosclerotic groups. These differences were decreaslngly significant at 250 cps (Observed “ 2-V2> J. .01 - 2-669. df = 58), 500 cps (tcbscrved - 2.86>t - 2.669, df - 5 8 ), 750 cp, - 2 .6 4 ^ t, ^ = 2 .0 0 , df “ 5 6 ), and 1000 cps Uobserved e ° ^ ! < 1 .50 " O*68* df * 54) • The stapedectomized and o to s c le ro tic mean t o t a l‘■impedance values were found to be significantly different at 250 cps (to5SerVed ” 3.91> 1 .001 ■ 3- 1*7 6 ' df = 58) * 500 cps - 1t.6 8 > t , 001 - 3 .^ 7 6 , df ** 57) , and 750 cps (tobserved - 2.89> t Q] - 2.724, df - 38). The obtained _t-score for 1000 cps was not significant (J^bgerygd “ 0.36 t, “ 0.683, df - 30). As suggested by Ferguson (19), when assumptions for the _t-test cannot be met, a non-parametric statistic should be considered since they are 11 independent of the shapes of the distributions In the popula tions from which the samples are drawn." For this purpose, the Kruskal-Wal1 Is one-way analysis of variance (71) was employed in the analysis of all data for the three subject groups. This procedure was especially applicable since values that exceeded the lim it of the acoustic bridge could be used In the analysis since they were assigned a ranked value. Siegel (71) indicates that when a significant number of tied values occur, the resultant value of the analysis, H, tends to become less sensitive to group differences. When corrected for ties, 69. the values of H become more significant; however, in this study all values of H were significant (p<.001) and correction for ties was not necessary. These analyses are summarized in Table 5* To exemplify the significant differences obtained for all compared scores by the previously mentioned non-parametric procedure, one example is presented. The to ta l impedance values fo r the normal and stapedec- tomized groups were found to be from different populations on the basis of the H-values obtained at 250 cps (H0t>servecj * 1^3*82->X^ #goi « 10.83, d f - 1 ), 500 cps (Hobserved - I4 8 .4 I> X Z -0 0 , = 10.83, d f = I ) . 750 cps ^observed “ ^.70> X2 -00| - 10.83, df - I , and 1000 cps 137-9^ X ool ” ,0*83, df = 1). The remaining comparisons can be interpreted in the same contextual manner from the values listed in Table 5. The fin d in g , as previously ind icated , that the impedance values at 500 cps were apparently the best differentiating measures is substan tia te d by the H-values of Table 5 , e s p e c ia lly between the normal and stapedectomized subjects. In other words the graphic analyses, some of the t.-tests and the non-parametr ic Kruskal-Wal 1 is one-way analysis of variance, all indicated that the most significant difference occurred a t 500 cps fo r to ta l impedance. On the basis of the preceding statistical analyses, the firs t null hypothesis was rejected. In line with the stated rejection of this hypothesis, the results from one subject diagnosed as having otosclerosis by an otologist should be discussed. This particular subject was confirmed as having this condition during surgery. The 7 0 . Table 5. H values associated with the Kruskal-Wal1 is one-way analysis of variance showing the differences between the comparisons of mean measures of to ta l impedance, compliance, and resistance fo r 40 normal hearing subjects, 40 stapedectomlzed subjects, and 20 otosclerotic subjects at the four test frequencies of 250, 500, 750, and 1000 cps. Tabled values greater than H ■ 10.83 are significant, p <.001 (X^, 1 df). IMPEDANCE C0MPLIANCE RES I STANCE cps (ohms) (v o l. cc) (a rb itra ry ) Normals vs. 250 143.82 143.67 149.13 Stapedectomized 500 148.41 151.19 149.00 750 146.70 144.33 133.85 IK 137.94 142.97 129.88 Normals vs. 250 56.33 86.56 39.18 Otosclerot ic 500 57.76 65.76 56.86 750 5 6 .0 8 56.90 58.38 IK 64.17 56.32 59.65 Stapedectomized vs. 250 69.49 119.96 77.58 O tosclerot ic 500 62.83 107.36 58.63 750 61.04 116.84 57.66 IK 55.37 108.80 54.99 71. otologist stated that the footplate of the stapes was "extremely fixed." The scores to be discussed for the otosclerotic subject MB are listed in Appendixes D and E for Subject 5. Subject MB displayed an air-bone gap that has been associated with otosclerosis by many workers, for example Newby (57). As listed in Appendix E, the air-bone gaps for this subject were found to be 50 dB a t 250 cps and 45 dB a t 500 cps. The acoustic-impedance measures of this subject did not coincide with the typical otosclerotic values th a t have been described by Zwislocki (89) and Feldman (16) or the mean values that were obtained In the present study. For the reader's reference, mean values for normal subjects as taken from Table I w ill be given after Subject MB’s scores in order to demonstrate the p o s s ib ility of m is in te rp re ta tio n of the acoustic Impedance resu lts alone. The equivalent compliance scores for MB were as follows: 250 cps, .50 (.5 2 ); 500 cps, .60 (.£ 2 ) ; 750 cps, U20 (1 .0 7 ): and 1000 cps, 1.80 (1 .45). The arbitrary resistance scores for MB were as follows: 250 cps, 22 (2 3 ); 500 cps, 25 (2 £ ); 750 cps, 28 (2 2 ); and 1000 cps, 36 (22). The total impedance scores in acoustic ohms for MB were as follows: 250 cps, 1893 (1937); 500 cps, 836 (838); 750 cps, 363 (5 30 ); and 1000 cps, 183 (4 13 ). In all instances, MB's scores approximated the mean values of the normal subjects, and his scores were always directionally deviant from the values of the normal subjects that in turn were more like the stapedectomized subjects. For example, his to ta l impedance score a t 250 cps (1893) is less than the mean normal value of 1937> whereas 72. the mean value for the stapedectomized group was 303^ (from Table 1). MB is one of four subjects tested, with confirmed otosclerosis at surgery, who demonstrated acoustic impedance values that were indica tive of values obtained from normal or stapedectomized subjects. Again, the measures obtained from this subject are presented to emphasize the importance of not u t iliz in g acoustic Impedance measures as a definite indication of otosclerosis. Hypothes is 11; Hear ing Sens Itiv itv and Impedance. There is no relationship between the acoustfc-impedance measures and the relative differences between air-conduction and bone-conductIon sensitivity for subjects with (a) normal-hearIng sensitivity, (b) otosclerosis, and (c) stapedectomy. This hypothesis was tested by correlating total - impedance values with relative air-bone gap values (as listed in Appendix E) for all subjects at 250 and 500 cps. Scatter diagrams and correlation values obtained with the Pearson Product-Moment correlation procedure (19) are presented In Figures 22 and 23. No attempt was made to correlate the measures obtained at 750 and 1000 cps due to the increased variance and the diminished number of scores obtainable. The correlation values, r, obtained at 250 cps (r. t , = .312> r ni = -256, N * 100) and at r obtained *01 500 cps (retained “ *209>r ^ «■ .197, N » 99) were moderately s ignlfleant. The c o rre la tio n s between these two measures were not as high as might be anticipated based on theoretical grounds. For example, subjects with otosclerosis (with a fixed stapes as reportedly described 73. 10 Krr r-.312_ J? f — t— X _ -XA- j X Ix A X * -xxx- XX XX X ; X XXX in XX. t E n * 1 K - 1 _ AX -A- O z t < i A Q LU A $ 0. A 4 £ 46 A 4 4 O H I--- x m EE 100 L : 1 : m - 1 0 O 10 20 30 40 RELATIVE AIR-BONE GAP (dB) Figure 22. A s catter diagram of measures of impedance (ordinate) vs relative air-bone gap (abscissa) for AO subjects with normal-hearIng sensitivity, 40 with stapedectomy, and 20 with otosclerosis obtained a t 250 cps. 74. 10 K V) E < LL1Q t t . < ee» O 100 RELATIVE AIR-BO NE GAP (dB) Figure 23. A s c a tte r diagram of measures o f Impedance (o rd in ate) vs relative air-bone gap (abscissa) for 40 subjects with normal-hearIng sensitivity. 39 with stapedectomy, and 20 with otosclerosis obtained at 500 cps. by Goodhill in Chapter II) should demonstrate an air-bone gap (57) and high acoustic impedance (89)• This combination of measures should place the representation of otosclerotic subjects in the upper right quandrant of the scatter diagrams in Figure 22 or 23. In some instances this Is the case, as can be observed for some of the otosclerotic subjects in these figures. On the other hand, the normal subjects might be expected to group around the mean total Impedance and mean a ir- bone gap values, which they do as shown in Figures 22 and 23. The co-ordinate loci of the stapedectomized subjects could be expected to f a ll near the normal subjects, provided that the Impedance values returned toward the mean values of the normal subjects and that the air- bone gaps diminished to values within the range obtained for the normal subjects. The second null hypothesis was rejected on the basis of statisti cal analysis. However, because of the low c o rre la tio n values, measures of acoustic impedance should be carefully interpreted In relation to hearing s e n s itiv ity . In other words impedance measures appacently do not provide a means of predicted hearing sensitivity. The importance of the above finding relates to the individual subject (MB) described under the discussion of the firs t null hypothesis. If a subject can be presumed to have otosclerosis and the stapes is fixed, theoretically high impedance could be expected as described by Zwislocki (89), in addition to an air-bone gap. The high impedance value can be anticipated, according to Zwislocki, since the impedance at the stapes footplate Is increased by its fixation. Then If the ossicular chain was able to relay th is increased impedance to the eardrum, it could be detected as an abnormal increase in acoustic impedance. Such high impedance measures were obtained from some otosclerotic subjects (see for exampie the high values of otosclerotic Subject 1, CS, as listed in Appendix D). As pointed out in the discussion of the f i r s t hypothesis, the values of acoustic impedance obtained from confirmed otosclerotic subjects, were not necessarily high in magnitude. Therefore some factors are apparently causing acoustic-impedance measures obtained from some o to s c le ro tic subjects to approximate values obtained from normal subjects, in spite of the air-bone gap exhibited by the subjects with otosclerosis. Hvoothes is 111: Acoust tc Ref 1 ex Time Delay. There is no d iffere n c e between the delay of a change in acoustic impedance in response to a noise stimulus In the contralateral ear for subjects with (a) normal-hear ing sensitivity and (b) stapedectomy. Recordings of 120 acoustIc-reflex responses from 10 subjects w ith normal-hearing s e n s itiv ity were measured w ith a m illim e te r ru le calibrated to .1 mm in order to determine the distance between the onset of the stimulus In the opposite ear and the onset of an impedance change in the Impedance-measured e a r. The 120 measurements (s ix from each ear) obtained from the ten subjects with normal-hearIng sensitivity are listed In Appendix F. For comparison, one typical response from a normal subject (JO) and one typ ical response from a stapedectomized subject (CB) , are presented in Figure 2*f. innnnnnnnnnnnnnnnnnnnnnnnnn nrin n n JO © -XopenKogeri^ Type "Op 2351 - Com r-^ c - C-C C t C < < C C^C 1 1 I mm" .'«* ■ ' ' - '0 O O 0 0 U O O G C O 0 O 0 O O O O G 0 C C O C O 0 C 0 D O o CM-JgL -irfcr BrOeTSi Kjaer - Copent ’- O C Figure 24. Examples of single Impedance change responses from one normal hearing- sen sitivity subject and one stapedectomized subject. Stimulation In the opposite e*> we* 88 dB SPL of white noise; stimulus onset Is Indicated by the arrow. 78. The mean delay determined from the above measures was 5.8 mm. This value was multiplied by the paper speed (30 mm/sec) resulting In a mean delay time of 17*+ msec. Subtraction of the delay time of the instrumentation (20 msec), which was described in the previous chapter, yielded the mean delay time of 15*+ msec. This time represents the amount of time between the stimulus (88 dB SPL of white noise) onset In one ear and impedance change in the opposite ear. The same type of recordings for 10 stapedectomized subjects did not reveal any responses as detected with the instrumentation employed in the present study. On the basis of these findings the third null hypothesis was rejected. The absence of an acoustic reflex in man has been reported by several Investigators (13, 33, 62). In general, they proposed that the tensor tympani muscle does not respond to acoustic stimulation. On the other hand, Weiss and others (81) reported responses to acoustic stimu lation that, according to them, indicated a response from the tensor tympani muscle in subjects with normal-hearing sensitivity. In addition they reported a response from a stapedectomized subject that suggested a response from the tensor tympani muscle, even though the stapedius muscle could no longer affect the impedance measured at the eardrum. The results of this study appear to be In agreement with the former point of view at least when the stimulation intensity of the opposite ear is 88 dB SPL. No Inferences can be made regarding higher intensity levels; however, the responses obtained from the ten 79. stapedectomized ears used in this study tend to indicate that continually changing impedance characteristics, as suggested by Simmons (72), are not in evidence as found in subjects with normal middle-ear structures. CHAPTER V SUMMARY AND CONCLUSIONS The purpose of this study was to investigate some aspects of middie-ear functioning on the basis of measures of acoustic impedance from 40 subjects with normal-hearing sensitivity, 40 with stapedectomy, and 20 with otosclerosis. The relationship between total impedance and relative air-bone gap, and the nature of an acoustic reflex after severance of the tendon of the stapedius muscle were also investigated. Measures of acoustic impedance and hearing sensitivity to a ir - conducted and bone-conducted stimuli were determined at the frequencies of 250, 500, 750, and 1000 cps for a ll subjects. The delayed onset of reflexive middie-ear impedance changes in response to a series of six 88 dB SPL white-noise stimulations in the opposite ear were also determined at the carrier frequency of 500 cps for 10 subjects with normal-hearIng sensitivity and for 10 subjects with stapedectomy. The statistical analysis of the obtained data indicated significant differences between mean total impedance values of the three subject groupings, especially at 500 cps. Significant differences were also noted between mean equivalent compliance and arbitrary resistance measures. A modestly significant relationship between total impedance and air-bone gap was noted at 250 and 500 cps using the pooled data of 100 subjects. 80. 81. The average of 120 responses from 10 subjects with normal- hearing sensitivity indicated a 15** msec delayed onset of impedance change following contralateral acoustic stimulations. This mean response differed from the responses of the stapedectomized subjects since the latter group did not demonstrate a measurable impedance change under the same experimental conditions. On the basis of the results of this study, several conclusions are presented. a) Mean total-impedance measures, especially at 500 cps, differentiated the three states of middle-ear functioning better than the separate mean measures of equivalent compliance and arbitrary resistance. In comparison with mean impedance for subjects with normal hearing sensitivity, otosclerotic subjects demonstrated higher impedance values, whereas stapedectomized subjects showed lower values of impedance. b) The relationship between total impedance and relative a ir- bone gap was such that impedance values should not be inferred on the basis of hearing sensitivity. For example, when a subject demonstrated a substantial conductive hearing loss that was attributable to otoscle rosis, the acoustic Impedance measures from this subject could be relatively "normal" rather than the higher values that might be predicted from the mean impedance scores for otosclerotic subjects. These two measures were found to be more meaningful when displayed co-ordinately on the same graph. c) The findings of this study also support the notion that the tensor tympani muscle does not respond to moderate acoustic stimula tion when the stapedius tendon of the same ear has been severed. However this finding is based only on a white-noise stimulus of 88 dB SPL. Future experimentation based on this study could determine the precise frequency at which compliance values exceed the volume lim it of the Zwislocki Acoustic Bridge for stapedectomized subjects. This procedure could be accomplished by adjusting a continuously variable osscillator and the bridge until a null point is obtained at a volume of 5 cc and some resistance value. Measures obtained in this manner may be of some value in determining abnormal functioning of an altered middle ear. Another experiment might establish a response from the tensor tympani by tac tile stimulations as suggested by Klockhoff (30) and Ojupesland (12); subsequently more intense acoustic stimuli could be used to determine whether the tensor tympani muscle w ill respond under these conditions. 83. APPENDIX A. The results of test-retest measures of acoustic impedance. As mentioned in Chapter I I I , some subjects were not tested in the sound-treated room. In addition, the audio-signal generator was replaced by a portable audiometer (Beltone, Model 10-C) as the signal source for the acoustic bridge. Under such conditions two main sources of error might be expected: (a) increased ambient noise and (b) frequency differences between the signal sources. To determine the relationship between the measures obtained under these two conditions, the following p ilo t study was conducted. Ten subjects of the 40 normal-hearing subjects were randomly selected and retested in an environment that was classified as not sound treated, that is, the ambient noise level of the environment was not specifically controlled. Such conditions were anticipated for the testing of those subjects that would be seen In the offices of the several cooperating otologists. Each subject was prepared, as described in Chapter I I I , for the measures of acoustic impedance as though this was the fir s t test occasion. The experimenter was not aware of any of the previous impedance measures, size of sealing tip used, etc. The retest scores were recorded in equivalent volume (cc) for compliance and arbitrary units for resistance. These data were then correlated with the scores obtained from the same subjects In the sound-treated room using the Spearman rank correlation (71). Table 6 is a listing of the resultant correlation 8k. coefficients for compliance and resistance at the four test frequencies, 250 cps, 500 cps, 750 cps, and 1000 cps. Table 6. Spearman rank correlation coefficients for test retest compliance and resistance measurements. 250 cps 500 cps 750 cps 1000 cps Compliance in equivalent volume (cc) rho ® . 8 5 p < * 0 1 . 9 7 P < . 0 1 . 8 8 p< .01 . 9 3 p < . 0 1 Resistance in arbitrary units rho » .91 P <.01 . 8 8 p <*01 . 8 6 p < .0 ! . 8 8 pC.Ol On the basis of the foregoing results, it was fe lt that there was sufficient agreement between the two testing environments to ju s tify using data obtained from both* 85. APPENDIX B. Raw scores for compliance, in equivalent volume (c c ), and the arbitrary resistance values for the 40 normal hearing subjects. These data are also listed in acoustic ohms as reactance and resistance. The combined total impedance as determined by vector analysis is also shown. The values are listed for each of the four test frequencies. 250 cps Compliance Res istance Reactance Res istance n/ Subject cc volume arb i trary ohms ohms ohms 1. JS .52 22 1752 500 1322 2. 0T .30 25 3036 350 3056 3. JS .65 27 1401 300 1433 4. YT .70 27 1301 300 1335 5. JG .48 24 1879 400 1921 6. KA .40 20 2277 600 2355 7. CL .44 22 2070 500 2130 8. BM .40 20 2277 600 2355 9. CA .80 23 1138 450 1224 10. VS .60 25 1518 350 1553 1 1 . BG .60 20 1518 600 1632 12. SB .73 25 1248 350 1296 13. LT .58 21 1570 550 1664 14. KW .50 22 1826 500 1893 15. 02 .65 24 1401 4oo 1457 16. SS .52 20 1752 600 1852 17. JO .31 27 1000 300 1044 18. SP .80 22 1138 500 1243 19. BW .40 18 2277 800 2413 20. DG .30 24 3036 400 3062 21. BG .30 20 3036 600 3095 22. RW .83 26 1097 330 1146 23. JF . 60 22 1518 500 1593 24. JK .40 23 2277 450 2321 -£ *. JO .50 23 1826 450 1881 26. PC .55 25 1656 350 1693 27. JG .45 21 2024 550 2097 28. TM .30 20 3036 600 3095 29. LS .60 25 1518 350 1558 30. MS .55 19 1656 700 1798 3U GS .30 20 3036 600 3095 32. BS .33 22 2760 500 2805 33. RB .55 20 1656 600 1761 34. LC .45 25 2024 350 2054 35. RH .50 22 1826 500 1893 36. MR .55 24 1656 400 1704 37. SW .60 22 1518 500 1598 38. PM .6 5 26 1401 330 1439 39. RD .40 23 2277 450 2321 40. PR .52 20 1752 600 1852 86. 500 cps Comp]iance Res I stance Reactance Res istance n t Subj ect cc volume arbitrary ohms ohms ohms 1. JS .54 22 843 500 930 2. OT .52 23 876 450 985 3. JS .85 26 536 330 629 4. YT .85 27 536 300 614 5. JG .55 28 828 260 868 6. KA .80 22 569 500 757 7. CL . 60 24 759 400 858 8. BM .55 24 828 400 920 9. CA 1.00 24 455 400 606 10. VS .63 27 723 300 783 11. BG .30 25 569 350 668 12. SB .95 26 479 330 582 13. LT .80 24 569 400 696 14. KW .60 24 759 400 858 15. DZ 1.00 27 455 300 545 16. SS .55 22 828 500 967 17. JO 1 .10 27 414 300 511 18. SP 1.30 28 350 260 436 19. BW .50 23 911 450 1016 20. DG .30 25 1518 350 1558 21. BG .40 25 1136 350 1139 22. RW .95 28 479 260 545 23. JF .65 23 701 450 333 24. JK .50 24 911 400 995 25. JO .70 24 651 400 764 26. PC .65 28 701 260 748 27. JG • 70 22 651 500 821 28. PM .40 23 1136 450 1222 29. LS .80 30 569 220 610 30. MS .80 21 569 550 791 31. GS .30 23 1518 450 1583 32. BS .40 26 1136 330 1183 33. RB .60 24 759 400 858 34. LC .50 28 911 260 947 35. RH .70 24 651 400 764 36. MR .62 25 735 350 814 37. SW .85 24 536 400 669 38. PM 1.00 27 455 300 545 39. RD .50 26 911 330 969 40. PR .80 20 569 600 827 87. 750 cps Compliance Res istance Reactance Res istance /Z/ Subject cc volume arb i trary ohms ohms ohms 1. JS .73 23 416 450 613 2. OT 1.40 24 217 400 455 3. JS 1.05 25 289 350 454 4. YT 1 .10 25 276 350 446 5. JG .72 28 422 260 496 6. KA 2.20 24 138 400 423 7. CL .66 25 460 350 578 8. BM .70 25 434 350 558 9. CA 1.22 27 249 300 390 10. VS .95 28 320 260 412 11. BG 1.40 26 217 330 395 12. SB 1.55 27 196 300 358 13. LT 1.50 23 202 450 493 14. KW 1.65 25 184 350 395 15. DZ 1.80 24 169 400 434 16. SS .55 22 552 500 745 17. JO 1.25 29 243 240 342 18. SP 2.60 30 117 225 254 19. BW . 60 24 506 400 645 20. BG • 30 27 1012 300 1055 21. BG .45 25 675 350 760 22. RW 1.20 31 253 210 329 23. JF .70 25 434 350 558 24. JK .60 24 506 400 645 25. JO 1.00 26 304 330 449 26. PC .85 28 357 260 442 27. JG 2.50 21 121 550 563 28. TM .50 22 607 500 786 29. LS 1.65 32 184 190 264 30. MS .85 20 357 600 698 31. GS .30 25 1012 350 1071 32. BS .50 27 607 300 677 33. RB 1.20 25 253 350 432 34. LC .85 30 357 225 422 35. RH 2.10 30 144 225 267 36. MR .80 27 380 300 484 37. SW .85 25 357 350 500 38. PM 1.30 28 234 260 350 39. RD , 60 30 506 225 554 40. PR .65 17 467 900 1014 88 1000 cps Compliance Resistance Reactance Resistance /Z / Subject cc volume arb i trary ohms ohms ohms I. JS • 74 24 307 400 504 2. 0T 2.40 24 95 400 411 3. JS 2.00 27 114 300 321 4. YT 1 .80 25 126 350 372 5. JG 2.10 28 108 260 232 6. KA 2.40 28 95 260 277 7. CL • 71 28 321 260 413 8- BM .95 28 240 260 354 9. CA 1.70 27 140 300 331 10. VS 1.55 32 147 190 240 11. BG 1.80 29 126 240 271 12. SB 1.95 28 117 260 285 13. LT 1.70 22 140 500 519 14. KW 2.40 23 95 450 460 15. DZ 1.95 25 117 350 369 16. SS .55 25 414 350 542 17. JO 2.55 36 89 140 166 18. SP 3.80 33 60 170 180 19. BW 1.10 27 207 300 364 20. DG .30 28 759 260 802 21. BG .45 24 506 400 645 22. RW 1.60 30 142 225 266 23. JF 2.55 26 89 330 342 24. JK .40 24 569 400 696 25. JO 1.30 27 175 300 347 26. PC 1.20 27 190 300 355 27. JG 1.60 24 142 400 423 28. TM .60 22 379 500 627 29. LS 5+ 30 225 30. MS • 95 21 240 550 600 31. GS .35 27 651 300 717 32. BS 1.00 28 228 260 346 33. RB 4.80 28 47 260 264 34. LC 2.00 30 114 225 252 35. RH 5+ 30 225 36. MR 1.25 29 182 240 301 37. SW .90 28 253 260 363 38. PM 1.90 27 120 300 323 39. RD .70 24 325 400 515 40. PR .80 18 285 800 849 89 APPENDIX C. Raw scores for compliance, in equivalent volume (cc) , and the arbitrary resistance values for the 40 stapedectomized subjects. These data are also listed in acoustic ohms as reactance and resistance. The combined to ta l impedance as determined by vector analysis is a lso shown. The values are listed for each of the four test frequencies. 250 cps Comp)iance Res istance Reactance Res istance m Subj ect cc volume arbitrary ohms ohms ohms 1. HT 1.05 30 867 225 396 2. JS .30 20 3036 600 3095 3. LM .70 26 1301 330 1342 4. ES .90 28 1012 260 1044 5. DA .40 24 2277 400 2311 6. DA .40 25 2277 350 2304 7. FT 1.10 32 828 190 850 8. AN .50 26 1826 330 1856 9- CB .90 32 1012 190 1030 10. BR 1.10 33 828 170 845 11. RM 1.30 30 701 225 736 12. MD 1.30 31 701 210 732 13. KM 1.60 35 569 150 588 14. MM .30 17 3036 900 3167 15. MK 1.20 30 759 225 792 16. EC 2.20 40 414 105 427 17. EM 1.15 27 792 300 847 18. FH 1.40 30 651 225 858 20. JB .80 26 1138 330 1185 21. EM 1.90 41 **79 100 489 22. CS .20 20 4554 600 4593 23. FM 1.80 29 506 240 560 24. IP 1.30 33 701 1 70 721 25. FC 1.70 40 536 105 546 26. MY .80 28 1138 260 1167 27. AN .75 23 1214 450 1295 28. MG .60 27 1518 300 1547 29. RM .80 30 1138 225 1160 30. OB 2.00 34 454 160 481 31. MO .75 30 1214 225 1235 32. MJ .80 30 1138 225 1160 33. MK 1.20 30 759 225 792 34. DC 2.50 40 364 105 379 35. FT 1.40 37 650 130 663 36. HT .90 32 1012 190 1030 37. ES .40 27 2277 300 2296 38. JS .20 16 4554 1000 4663 39. LM 1.10 29 828 240 862 40. BR 1.90 37 479 130 496 90. 500 cps Compllance Res 1 stance Reactance Res istance /Z/ Subject cc volume arbi trary ohms ohms ohms 1. HT 3.25 36 140 140 198 2. JS .35 21 1301 550 1412 3. LM 1.50 30 304 225 373 4. ES 1.20 32 380 190 425 5. Da • 50 26 911 330 969 6 . DA .50 27 911 300 959 7. FT 1.50 35 304 150 339 8 . AN .65 29 701 240 741 9. CB 1.00 37 455 130 473 10. DR 1.40 39 325 110 343 11. RM 3.00 32 152 190 243 12. MD 2.00 28 228 260 345 13. km 3.00 35 152 150 214 14. MM .50 22 911 500 1039' 15. MK 1.80 30 253 225 339 16. EC 4.00 45 114 75 136 17. EM 1.20 23 380 450 589 18. FH 2.20 35 207 150 256 19. RF 2.20 34 207 160 262 20. JB 1.10 29 414 240 479 21. EM 4.80 45 95 75 121 22. CS .35 22 130 500 517 23. FM 4.60 33 99 170 197 24. IP 3.50 34 130 160 206 25. FC 4.10 43 111 90 143 26. MY . 1.60 30 285 225 363 27. AN 1.00 27 455 300 545 28. MG .80 25 569 350 668 29. RM .90 30 506 225 554 30. OB 3.50 40 130 105 167 31. MO .90 32 506 190 540 32. MJ 1.00 35 455 150 479 33. MK 2.10 32 217 190 288 34. DC 5+ 45 75 35. FT 2.10 40 217 105 241 36. HT 1.00 35 455 150 479 37. ES .40 28 1136 260 1165 38. JS 4.80 42 95 95 134 39. LM 4.00 34 114 160 196 40. BR 3.40 39 134 110 173 91 750 cps Compliance Res istance Reactance Res istance /!/ Subject cc volume arbitrary ohms ohms ohms 1. HT 4.00 34 76 160 177 2. JS .35 24 867 400 955 3. LM 5+ 25 350 4. ES 1.20 25 253 350 432 5. DA 1.00 28 304 260 400 6. DA .80 29 380 240 449 7. FT 3.50 35 87 150 173 8. AN 1.65 27 184 300 352 9. CB 2.10 42 144 95 173 10. BR 3.90 37 78 130 152 11 . RM 5+ 22 500 12. MD 5+ 32 190 13. KM 5+ 35 150 14. MM .70 22 434 500 662 15. MK 3.50 32 87 190 209 16. EC 5+ 35 150 17. EM 4.90 35 62 150 162 18. FH 5+ 30 225 19- RF 5+ 30 225 20. JB 5+ 28 260 21. EM 5+ 33 170 22. CS .30 25 1012 350 1071 23. FM 5+ 28 260 24. IP 5+ 35 150 25. FC 5+ 30 225 26. MY 5+ 30 225 27. AN 1.65 27 184 300 352 28. MG 1.50 29 202 240 314 29. RM 1.00 35 304 150 339 30. OB 5+ 30 225 31. MO 2.50 35 121 150 193 32. MJ 4.00 35 76 150 168 33. MK 4.80 31 63 210 2)9 34. DC 5+ 30 225 35. FT 5+ 42 95 36. HT 1.20 35 253 150 294 37- ES .50 30 607 225 647 38. JS .40 18 759 800 1103 39. LM 5+ 24 400 4+0. BR 5+ 35 150 92. 1000 cps Compliance Res istance Reactance ResIstance /Z/ Subject cc volume arb i trary ohms ohms ohms 1. HT 4.80 25 47 350 353 2. JS .40 • 28 569 260 626 3. LM 5+ 22 500 4. ES 1.00 27 228 300 377 5. DA 1.20 30 190 225 294 6. DA 2.30 30 99 225 246 7. FT 5+ 32 190 8. AN 4.50 27 51 300 304 9. CB 5+ 35 150 10. BR 4.50 30 51 225 231 ] I . RM 5+ 20 600 12. MD 5+ 25 - 350 13. KM 5+ 30 225 14. MM l .50 22 150 500 522 15. MK 5+ 27 300 16. EC 5+ 30 225 17- EM 5+ 27 300 18. FH 5+ 27 300 19. TJ 5+ 25 350 20. JB 5+ 28 260 21. EM 5+ 25 350 22. CS .30 25 759 350 836 23. FM 5+ 25 350 24. IP 5+ 28 260 25. FC 5+ 25 350 26. MY 5+ 25 350 27. AN 5+ 21 550 28. MG 3.80 25 60 350 355 29. RM 1.20 31 190 210 283 30. 08 5+ 25 350 31. MO 5+ 30 225 32. MJ 5+ 30 225 33. MK 5+ 28 260 34. DC 5+ 27 300 35. FT 5+ 30 225 36. HT 1.20 38 190 115 222 37. ES .70 34 325 160 362 38. JS . 60 23 379 450 588 39. LM 5+ 21 550 40. BR 5+ 30 225 93. APPENDIX D. Raw scores for compliance, arbitrary resistance, react ance, acoustic resistan ce, and to ta l impedance fo r 20 o to s c le ro tic subjects. These data are also listed in acoustic ohms as reactance and resistan ce. The combined to ta l impedance as determined by vector analysis is also shown. The values are listed for each of the four test frequencies. 250 cps Compliance Res istance Reactance Res istance a / Subject cc volume arbitrary ohms ohms ohms 1. CS .10 12 91 10 2000 9327 2. RH .20 18 4554 800 4624 3. RH .20 20 4554 600 4593 4. SB .10 11 9110 2200 9372 5. mb .50 22 1826 500 1893 6. MB .45 23 2024 450 2073 7. JM .60 25 1518 350 1558 8. JM .50 25 1826 350 1859 9. HM .90 31 1012 210 1034 10. HT • 70 32 1301 190 1315 11. NW 1.70 30 536 225 581 12. NW .60 27 1518 300 1547 13. MD .30 21 3036 550 3085 14. LS .40 25 2277 350 2304 15. MJ .40 25 2277 350 2304 16. FC .20 21 4554 550 4587 17. MO .40 28 2277 260 2292 18. J8 .50 27 1826 300 1350 19. FH .35 25 2602 350 2625 20. JB • 50 25 1826 350 1859 500 Cps 1. CS . 10 15 4554 1200 4709 2. RH .25 21 1822 550 1903 3. RH .20 21 2277 550 2342 4. SB .10 18 4554 800 4624 5. MB .60 25 759 350 836 6. MB .60 24 759 400 858 7. JM .80 30 569 225 612 8. JM .50 25 911 350 976 9. HM 1.40 33 325 170 367 10. NW 1.70 36 268 140 302 11. NW .90 29 506 240 560 12. HT .90 35 506 150 528 13. MD .30 25 1518 350 1558 14. LS .40 28 1136 260 1165 15. MJ .40 25 1136 350 1570 94 Compliance Resistance Reactance Resistance /Z / Subject cc volume arbitrary ohms ohms ohms 500 cps continued 16. FC .3° 24 1518 400 17. MO .40 30 1136 225 If 18 18. JB .55 30 328 225 858 19. FH .35 35 1301 150 1310 20. JB .60 30 759 225 792 750 cps 1. CS .20 17 1518 900 1765 2. RH .30 28 1012 260 1045 3. RH .25 25 1214 350 1263 4. SB .20 19 1518 700 1671 5. mb 1.20 28 253 260 363 6. MB .75 30 405 225 463 7. JM 1.40 35 217 150 264 8. JM • 70 35 434 150 459 9. HM 5+ 30 225 10. NW 5+ 30 225 11. NW 3-5 35 87 150 173 12. HT 1.50 35 202 150 252 13. MD .30 30 1012 225 1037 14. LS .40 30 759 225 792 15. MJ . 60 30 467 225 513 16. FC .40 25 759 350 836 17. MO . 60 35 467 150 490 18. JB .60 34 467 160 493 19. FH ,40 40 759 105 766 20. JB .80 30 1012 225 1037 1000 cps 1. CS .20 19 1140 700 1338 2. RH .50 28 455 260 524 3. RH .50 30 455 225 507 4. SB .30 25 759 350 836 5. MB 1.80 36 126 140 188 6. MB .85 34 268 160 312 7. JM 2.70 45 84 75 113 8. JM .70 35 325 150 358 9. HM 5+ 30 225 10. HW 5+ 25 350 95. Compliance Resistance Reactance Resistance /Z/ Subject cc volume arbitrary ohms ohms ohms 1000 cps continued 11 NW . 3.50 35 65 150 163 12. HT 2.50 34 91 160 184 13. MD .50 35 14. LS ^55 150 479 .55 35 ^ 150 440 15. MJ .60 25 380 350 517 16. FC .60 32 380 190 425 17. M0 .90 35 253 150 294 I S. JB .90 37 253 130 284 19. FH .40 40 569 105 579 20. JB 2.00 31 114 210 239 96 APPENDIX E. Raw scores of relative air-bone gap the normal, stape- dectomized, and otosclerotic subjects at the frequencies, 250 cps and 500 cps. A constant of +15 has been added to all scores to eliminate negative values. Normal Subjects Stapedectomized Subjects Subject 250 cps 500 cps Subject 250 cps 500 < 1. JS 10 05 1. HT 40 45 2. 0T 20 10 2. JS 25 15 3. JS 15 15 3. LM 20 40 4. YT 20 25 4. ES 30 15 5. JG 25 10 5. DA 15 15 6. KA 15 30 6. DA 15 15 7. CL 25 35 7. FT 20 25 8. BM 20 10 8. AN 15 15 9. CA 15 10 9. CB 25 15 10. VS 15 10 10. BR 15 10 11. BG 10 05 11 . RM 10 25 12. SB 15 20 12. MD 60 15 13- LT 25 20 13. KM 20 10 14. DW 10 20 14. MM 10 25 15. DZ 20 25 15. MK 20 55 16. SS 15 15 16. EC 15 15 17. JO 30 15 17. EM 60 60 18. SP 15 15 18. FH 25 25 19. BW 15 15 19. RF 15 15 20. DG 25 10 20. JB 10 15 21. BG 10 05 21. EM 20 60 22. RW 05 05 22. CS 10 10 23. JF 25 20 23. FM 15 10 24. JK 15 15 24. IP 30 20 25. JO 20 20 25. FC 10 15 26. PC 15 20 26. MY 20 15 27. JG 20 15 27. AN 15 10 28. TM 10 10 28. MG 25 15 29. LS 15 10 29. RM 15 40 30. MS 15 15 30. OB 15 15 31. GS 30 15 31. MO 15 35 32. BS 20 05 32. MJ 15 20 33. RB 05 15 33. MK 10 25 34. LC 15 15 34. KC 15 15 35. RH 15 15 35. FT 35 40 36. MR 15 15 36. HT 15 15 37. sw 15 20 37. ES 35 10 38. PM 20 15 38. JS 40 25 39. RD 20 15 39. LM 15 15 40. PR 25 20 40. BR 15 20 97. APPENDIX E continued Otosclerotic Subjects Subject 250 cps 500 cps 1. CS 70 70 2. RH 45 35 3. RH 50 55 4. SB 55 50 5. MB 50 45 6. MB 50 55 7. JM 40 45 8. JM 45 50 9. HM 55 55 10. HT 55 70 11. NW 50 35 12. NW 55 85 13. MD 55 65 14. LS 60 65 15. MJ 60 70 16. FC 45 55 17. MO 55 40 18. JB 60 55 19. FH 35 30 20. JB 45 55 98. APPENDIX F. Raw scores of the measured delayed onset of a change fn acoustic impedance in response to an acoustic stim u latio n in the contralateral ear. The listed scores are in mm and were obtained from both ears of ten subjects with normal-hearing sensitivity, six responses being obtained from each ear. 1. 7.0 31. 5.0 61. 4.0 91. 6.0 2. 8.0 32. 6.0 62. 6.5 92. 5.0 3. 8.0 33. 5.2 63. 6.5 93. 6.5 4. 7.9 34. 5.5 64. 5.5 94. 7-0 5. 8.0 35. 6.0 65. 5.0 95. 5.0 6. 8.5 36. 6.0 66. 4.8 96. 7.5 7. 5.0 37. 8.2 67. 3.0 97* 5.0 8. 6.5 38. 8.0 68. 6.0 98. 6.5 9. 8.0 39. 7.8 69. 5.5 99. 7.0 10. 7.0 40. 8.5 70. 5.5 100. 7.0 11. 6.0 41. 8.5 71. 5.5 101. 6.5 12. 7.0 42. 7.5 72. 4.0 102. 6.8 13. 7.0 43. 4.5 73. 7.0 103. 5.0 14. 5.5 44. 6.5 74. 5.5 104. 6.0 15. 5.8 45. 5.0 75. 5.5 105. 5.5 16. 4.5 46. 5.5 76. 6.0 106. 7.0 17. 5.8 47. 6.0 77. 5.5 107. 6.0 18. 5.5 48. 4.0 78. 6.0 108. 7.0 19. 5.3 49. 4.0 79. 6.0 109. 5.5 20. 6.5 50. 5.5 80. 5.5 110. 5.3 21. 8.0 51. 6.0 81. 6.0 111. 5.5 22. 5.5 52. 5.5 82. 5.5 112. 5.3 23. 4.8 53. 6.8 83. 6.5 113. 5.0 24. 3.2 54. 5.0 84. 4.0 114. 4.8 25. 4.2 55. 3.5 85. 5.5 115. 5.0 26. 4.5 56. 4.0 86. 7-0 116. 5.0 27- 4.8 57. 4.2 ’ 87. 6.0 117. 5.2 28. 4.0 58. 4.0 88. 8.0 118. 4.8 29. 4.7 59. 3.5 89. 8.2 119. 4.5 30. 4.5 60. 4.5 90. 7-0 120. 4.5 BIBLIOGRAPHY 1. 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