A method of impedance reflexometry was used to examine 101 students with hearing impairment in order to clarify the interrelation between speech discrimination and the state of the middle ear muscles. Ability to discriminate speech signals depends to some extent on the functional state of intraaural muscles. Speech discrimination was greatly impaired in the absence of stapedial muscle acoustic reflex, in the presence of low thresholds of stimulation and in very small values of reflex amplitude increase. Discrimination was not impeded in positive AR, high values of relative thresholds and normal increase of reflex amplitude in response to speech signals with augmenting intensity

Bazarov, V. G.

Moroz, B. S.

Sachenko, S. V.

English

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NASA. TECHNICAL MEMORANDUM	 NASA TM-76408
ROLE OF THE MIDDLE EAR MUSCLE APPARATUS
IN ISMS OF SPEECH SIGNAL DISCRIMINWION
B. S. Moroz, V. G. Bazarov and S. V. Sachenko
Translation of "Mysheciinyy apparat srednego ukha
v mekhanizmakh raspoznaniya rechevykh signalov,"
Zhurnal Ushnykh, Nosovykh i Gorlovykh Bolezney,
No. 5, Sep-Oct 1979, pp 24-28
(NASA-TM-7b4Ud) RULE Ok THE MIDDLE EAR 	 Nbl-13018
MUSCLE APPAiiAIUS It) MECHANISMS OF SPEE.C:h
SIGNAL DISCRiMiNAIIUN (National Aeronautics
tiad Space Administratio =t) 	10 1=	 UuC.Laa
HC AJ2/MF AU 1
	 CSCL +JbP G5/52 4004
NATIONAL AERONAUTICS LAND SPACE ADMINISTRATION
WA.SHIlMUI, D. C. 20546
	 OCTOBER 1980
IAA TM-'10408
RcXX OF TILE MIDDLE EAR MUSCLE
	 October 1980APPARATUS IN MW IANISMS OF SPEE: SI(2M
DISCRIbIMATION
	 °"Jj- 1"',- ' -.V
13. S. tbroz, V. G. E3azarra and S. V. Sachenk0 
	
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Leo Kanner Associates
.F°r i"" ter, 't «+9t" i':..>,	 . rr^r.
itxh000d City, California 940b3
	 Translation
dational Aeronautics ukl Space Administration
Washington, D. C. 2054b
Translation of "Myshecluiyy apparat srednego ukha v mekhanizmakh
raspoznavaniya redievykh siclrkilov", .,hurnLal Uslinykh, Nosovykh i
k,orlovykh Poll-.%Wy, No. ` 1 , Sop-h^,,t	 f'1` : ^-.'t1
A " method of i1i"ance refle.xaro:try was usai to examine 101 students
	
w
with hearing impairment in order to clarify the interrelation between
speech disc;riinination aril the state of the middle ear muscles. It spas
shcxni that ability to discriminate speech signals depends to some extent
on the functional state of intraaural muscles. -speech discrimination
was greatly impaired in the absence of stapedial muscle acoustic reflex ;m
(AR) , in t1)e presence of low thresholds of stimulation (up to 20 dB) and
in very small values of reflex amplitude increase. Discrimination was
not ht^eded in positive AR, high values of relative: thresholds (40 dB
or more) and normal increase of reflex amplitude in response to speech
sigwls wit ti augmeminq intensity.
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I4)W OF THh: MIDDI EAR MUSCLE APPAI2ATW IN
K)CHANISMi OF SPEMI SI('ML DISCRIMINM`21ON
B. S. Moroz, V. G. Bazarov and S. V. Saenko
Laboratory of Clinical AWiology and Vestibulology (Ilead, V. G, Bazarov)
of the Kolamiycluriko Scientific Resoarcti Institute for Otolaiyng+olex)y, Kiev
In the e>piniun of most investigators the basic physiological role of the mu- !)-4*
scalar apparatu s of Uie middle ear is related to protection of the receptor form-
ations o1 the ooc hlea against the adverse effect of local sounds (Moller, 1962;
Perlman, 1970; V. S. Olisov et al., 1976; B. M. Sagalovich et al., 1977; S. N.
Khecliinashvili, 1978). This is aChi.eved by reflex contraction of the intraaural
voscles and the accompanying diminution in the amount of acoustic energy reaching
the inner ear.
A nunbe:r of authors feel that, along with this prutaetive fEunction, the iris-;-
rles of the middle ear play a real role in creating optimal conditions for the ana-
lysis and discrimination of helpful signals as contrasted to noise (Simmons, 1964;
S. N. Kheclinashvili, 1978). Due to their action in frequency selection muscular
contractions facilitate dyiowl- , changes in they freLpyancy characteristic of the
transmission system of the middle ear, r educe the masking effect of low frequency
sounds and by tl^ vary fact create more favorable conditions for the emergence of
required sound signals. It has bieen theorized that the middle ear muscles parti-
cipate directly in binaural de-termination of sound source localization (Mollerr,
1963; Simmons, 1964; B. M. Sagalovich and A. A. Drozdov, 1973).
It is very interesting to con sider the data in respect to the effect of in-
ternal muscles on the piss of the reception and analysis of saws in the speech
spectrum. The research of Niemeyer (1971) , McCandless and Miller (1972), Dore and
Zakrisson (1973) has shown, that when the normal functioning of the middle ear mu-,
soles is impaircyl there is real. &-terioration in the intelligibility of speech,
especially for signals of great intensity -- on the order of 80 dB and higher.
These observations may be important in the practice of surgery for improving 1mr-
ing, in acoustic prosthesizing and in mt.,dical evaluation of hearing impairment.
* N rn xxs in the margin indicate pagination in tl),- foreign text.
1
Fig. 1. Graph of subject distribution
as a funct?.cm of the value of the re-
lative threshold for acoustic reflex
(AR) with stimulation by a 500 hz
tone for 800 microsec and of speech
intelligibility: a) value for acous-
tic reflex threshold (Ala) when ^^-I'p
< 20 dBt b) when - 21-40 dB, c) wh o
? 40 dB; N - number of subjects;
white column - good speech discrimin-
ation, shaded - poor.
1 ' 4
C
fl
co
F
c
Fig. 2. Graph of eject distribution as a
function of the value of the relative Al2l.'
' th tinnnslaticlnwhite sound and of
however, there has not yet been enough
^
ea
study done on participation of the m
scular apparatus of the middle r in
the mechani.sins for reception of speech
signals.
In this study we considered it im-
portant to clarify the existence of an
interrelation between speech sound dis-
crimination capability and the condi-
tion of the muscular apparatus of the
tympanic cavity in persons with neuro^-
sensory hearing .impairment. The solu-
tion of the problem may oper up new
possibilities in the area of acoustic
prosthesis, since the treatment of
such patients is still ineffectual and
is related basically to the prescrip-
tion of the proper hearing aid.
Vet: studied 101 students of grades
9 to 11 who were hard of hearing at
ages 17 to 21. In all of then. the de-
gree of impairment was practically
the same. 90% traced their condition
back to childhood in the wake of in-
W	 s	 by	 fectious diseawes (measles, pa otitis,
speech discrimination. Rest as above.
scarlet fever, flu) or followd.ng ad-
ministration of ototoxic antibiotics (streptmMcin, moncmycin, etc.) . When testing
was done audi.cmetrically in a soundproof booth on the -Fast German MA-30 apparatus.,
the loss of iznal hearing over a range of 125-8000 liz was from 50 to 90 d1l. White
sound thresholds in the subjects varied from 55 to 80 dB. In 57 spee&t test intel-
ligilibity was from 75 to 100%) in the other 43 it did not reach 75% even: with ma-
ximum strength signals (up to 110 dB) .
In otoscopy all subjects printed mobile unim-
paired tympanic diaphragms with clear oontours and
typical normal coloration. Persons with symptoms	 25
of bilmired function in sound conduction (scarred
tympanic diaphragm, perforations, tumefaction, etc.)
did not take part in the study.
Further a determination was made of the func-
tional condition of the adaptive muscular apparatus
of the middle ear on the basis of data obtained for
the threshold and amplitude of {the acoustic reflex
of the stapes muscle. For the examination we usea
e-Dapment of our own construction intended for dyna-
laic vqyeiance measurements (I3. S. Moroz and V. G. $a-
zarov, 1979). We measured the absolute acoustic
reflex threshold (ART a) in response to various Sound
stituli: square waves for wide band noise, tones
at 500 iiz lasting 800 microsec. For the ART we used
the decibel intensity of an acoustic stimulus that
ti
	
ti
w^.
h ^
i
t ` i
Fig. 3. Graph of subject
distribution as a fun--
tion of value for incre-
ment in amplitude of re-
flex anti sl	 i discrim-
ination; a) normal AR,
increment of amplitude,
b)higher SIR amplitude
values, lower values or
fence of acoustic re-
flex. white column for
good speech Ldscrimina-
tion, shaded for poor.
would cause contraction of the stapes muscle and we noted the change in the acoustic
impedance of the middle ear by 0.2-0.3 dB as conpared with the initial value. Here
the stylus went up 5-8 mm frau the baseline.
After determ lung the ART  we measured the amount of increment for AR amplitude
in percent when there was an increase in stimulus intensity by 10 dB above the thresh-
old of the reflex value, using the formula:
I ^ AlU ^ AU
	
100
0
where: I is the iaicr nt value for AR amplitude, A 0 is t e AR amplitude on the incep-
tion threshold (5-8 imi) and A10 is the AR amplitude in mni when the threshold is sur-
passed by an intensity of 10 uB.
At the same time we studied the relative thresholds for the acoustic reflex
(ART 0 ) typical of the value for acoustic pressure above the audibility threshold(AT) of sound reg ui red for the reflex to set in. The ARr 0 value was found with the
formula:	 ALUO =t ARPa - XT (dB) .
3
As a result of the nxk1surenwts for absolute threshold values of the AR we
establistwd that in 211 of the subjects the ART 
a 
values were 80-9U db i, i. e. they
matched the physiological norm. In b3% there was a variation in the range of
1OU-120 dB. The otlpr lb% Uf the students hard of hearing shawled no AR that we
succeeded in recording, a fact associated with severe hearing loss.
itesults analysis revealed that in 43 subjects gradual intensification of the
stimulus was accoapanied by a correspot)LAi pj linear in=tvmt in AR amplitude (I - /26
8U-15US) . while the other 58 persons showed no such proportional relationship be-
tween AR aniplittvAe and stimulus intensity. 71= t in a number of subjects we re-
corded a nonproportionally high inerenent in AR aaVlitude in response to a caipa-
ratively small increase in acoustic stimulus intensity (I - 3U0-400%),, whereas in
the other, on the contrary, the AR anVlitude increased very little w1m acoustic
intensity was inexeaseLi (I 0­4'0t).
w +_	 la	 f U-Je who e L SUDJresults far re-1 Ume W.I.,	 that out o	 1 10' subjectsect
22 presented ART, values equal to or less than 2U dB and 40 showed a threshold of
20-40 dB while 3-.1 showed 40 d1l. The indices obtained were convared with the data
from spo_KJ-i audicnetry (Figures 1. 2, 3). We were intrigued by the question: is
there any relationship wnatever between a person's ability to distinguish speech
sounds and t1w functional condition of the protective-adaptive mechanism of the
middle ear muscles?
Irm results shown in the 3 figures indicate the presence of a definite 131* be-
tween capacity to distinguish speech signals and the data from impedance reflexo-
metry. Thus, in the group under study in which we recorded low ART 0 values (to 20
dB), the number of pers(xis finding it hard to discriminate speech sounds was from
10 to 12 time=s greater than the number 14-so found it easy (Fig. la, 2a). Among the
persons whose MU 0 indices were in the range of 20-40 d13 (Fig. lb,, 2b) tlx--re were
no significant quantitative differences in respect to good or poor discrimination
of speech sourils. Yinally, in the group with high ART 0 values (above 40 dB) the
number of persons with food speemi discrimination was many times higher than the
number of those in -Axxn it was poor (Fig. 1c, 2c).
In analyzing results we also noted a definite relationship between speech dis-
crimination and the AR amplitude iix=emnt value (Fig. 3) . Thus, in the group in
4
which showed norrml physiological values for AR amplitude increment in response to
more and more intense stimuli (I - 51-150S) the number of persons with good speech
discrimination was 3 tines large: than those with poor. And contrariwise, among
subjects showing high AR amplitude increment values (I - 300-400%) or extremely lea
values (I - 0-50%) or no AR at all the number of persons with poor spec^;:h discrimin-
ation was larger than tnes number in whom it was good.
For further int -rpr:etatio ti of our results we rely upon t •.ne following literates
data.
1. The dynamic ran(je of clearly discriminated speech is 45-50 du (Yu. B.27
Preobrazhenskiy and L. S. Lkk inn 1973; M. M. Ffrusi, 1975) .
2. Maximal sjae4^n discrhTCL nation is achieved at sound levels equal to the
absolute values for tine ART (Rappaport, Tait . 1976) , which is on the whale only
10-15 dB 'glow discomfort level (McCanbless, biller, 1972) or a-10 dB above ttae
comfort level for loud spe€ i Wantis et al . , 19 x 6) .
3. The value for the relative VU that typifies the level of acoustic pressure
above t1w AT level required to trigger the AR nearly coincides or is slightly below
(by 10-15 dB) the value of thc: dynamic auditory range (Liden et al., 1973). Normal-
ly the relative ART is 66-75 dB (Moller, 1978) .
4. When the intensity of audiosignal,s is quite high the incipient contraction
of middle ear muscles irxluces further distortion of the sound and this results in
weaker speech discrimination (Liden et al., 1973; Rappaport, Tait, 1976).
on the basis of the literature data it is clear that quality reception and un-
derstanding of conversational speech requires a definite dynamic audiorange of 45-
60 dB. In this context one may explain the facts of poor speech discrimination in
student subjects when this audiorange was compressed (Fig. la, 2a). When they pre-
sented a wirier range, evidenced by the increase of the ARV  to 40 dB and higher
(Fig. lc, 2c), there was a considerable increase in their ability +x comprehend and
show good discrimination of speech signals. A similar explanation may be invoked
for the fact that in the group of the hard of hearing with a normal AR anpliitude
increment there is a predominance of persons with good speech discrimination (Fig. 3a) .
5
Evidently in this case the appearance of the AR IbIlowing muscular contraction
in the middle ear provides for better reception and better discrimination of speech
sounds. On the contrary, poor discrimination was observed in subjects without AR
­r in those where the reflex appeared but did not change in amplitude in response
to stimuli of varyin4 intensity (Fig. 3b).
At the same time
	 has also 4Lndi.cated that the ability of subjects to
discriminate speech ,somda is detenramed i!ot only by the dynamic audiorange and
the condition of the middle ear's muscular apparatus but it likewise a function of
other mechanisms. Thus, sans subjects with a narrow dynamic audiorange and nega
t,Lve All were found in our study to show good speech discrimination. At the same
time in the group of subjects with positive AR and relatively good dynamic audio
characteristics there were those wkao osould not discriminate speech signals very
well (Fig. lc, 2c) . Such discrepancies may be associated with r?dividual, quali- 	 /n8
ties of the CNS, particularly with the wmdition of the cortical portion of the
sound analyzer.
on the basis of the data obtained we may conclude that impedance reflexome-
try makes possible objective typing of the condition and reserves of residual
hearing in the hearing impaired and may find an application in working with hear-
ing aids. For example, on the basis of impedance changes we may decide on the
appropriate type of hearing aid for an individual patient as well as the proper
diet and type of work to be clone and we may make judgements about the need of
compression and about sound pressure levels.
Our research indicates,in persons lord of hearing yet having good dynamic
audio characteristics and speech discrimination, effective audi prosthesis may be
achieved by using those hearing aids which amplify speech signals linearly and
by frequency selection. Persons whose speech discrimunation is unsatisfactory and wIIO
nave poor dynamic characteristics need most of all special exercise:.z to develop
whatever hearing they have left using hearing aids which, while providing fre-
quency selection amplification, can set up a spectral combination, provide com-
pression of amplified sounds and also effect other acoustic transformations for
acYi.eving maximal screech understanding.
Thus, the results obtained open up new possibilities for increasing the effec-
a
tiverms of esthetic help for perwxw with serious foxes of nmrosertmory hearing
inVairment. Dare it seem proper that there be further study of the role of the
paddle ear muscles an the machmiam of speech sound discrimination.
7
1
.t
 Borg. E. 
r
and J. Za
.
krisson,	 o^;J. Aost. Soc. Amer.	
t 
525•-527 (197,,
,
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. i.ametry) , Mooccw, Enargiya Press , 1975.
3. Jantis, P, J. Millin and J. Shapixo, J. Sj ch Bear. Pes. 9, 178-193 (1966).
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5. Liden, G., B. Nordlund aixl I. Harkins, Acta Otolaryny. (Suppl.) 188, 275•-279
(1973) .
66 McCandless, C. A. and D. L. Miller, Ntl, a3ar. Aid J. 25, 7 (1972)
7. Moller, A. K., J. Aaoust. Soc. Amex. 34, 1524-1534 (1962).
B. Moroz, B. S. and V. G. j3azarov, zimm. ushn. nos. i Vrl. bolezney, 1, 115.117v
(1974).
9. Niemeyer, W., Audiology 10, 171-176 (1971) .
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i gorl. bolezney, 2 17-22 (1976).
11. Perlmann, h. B., Arch. Otoi^m 72, 201 .206 (197U).
12. i.'rL razhenskiy, Yu. B. and L. S. Godin, 2 novy s1^^ LrotezirovaniY-a
deteY (PrincIples of Bearing Ails for CTu 1dren] , Yosscow t Meditsina Press,
13. Rappaport, Z. and A. Tait, Arch. tkolaryng. 102, 129-132 (1976) .
14. Sagalovii 1, B. M. and A. A. Druzdov,v sb: Fizioiocji)2 i 4 21 qi a sluklka[in the collection Pgysiology and Patiwloyy of Hearing), Ito. ^8, 	 X76,
Moscow.
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16. Sizmis, F., elm. : W1.1 (St. L(xis) 73, 724 (1964) .
8


Role of the middle ear muscle apparatus in mechanisms of speech signal discrimination

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