The Effects of Probe-Tone Frequency on the
Acoustic-Reflex Growth Function
John J. Lutolf *
Honor O’Malley **
Shlomo Silman†
Abstract
Acoustic-reflex growth functions (ARGFs) were obtained from 20 normal-hearing listeners. Contralateral acoustic reflexes (ARs) were elicited with pure tones
of 2000 Hz. The magnitude of changes in static compliant susceptance (BA)
and conductance (GA) were monitored with probe-tone frequencies of 226
Hz, 678 Hz and 1000 Hz. ARGFs were obtained with six combinations of probetone frequency/admittance component: 226 Hz BA, 226 Hz GA, 678 Hz BA,
678 Hz GA, 1000 Hz BA, and 1000 Hz GA. Peak conductance (GA) and susceptance (BA) ARs were largest within the 678 Hz GA and 1000 Hz BA ARGFs,
respectively. Among high-frequency probe tones, the patterns of AR growth
were larger and less variable for the 678 Hz GA ARGF and the 1000 Hz BA
ARGF as determined by the magnitude of their linear (b1) and quadratic (b2)
polynomial coefficients and the value of their squared correlation coefficients
(R2).
Key Words: Acoustic reflex, acoustic-reflex growth function, probe-tone frequency, acoustic compliant susceptance, acoustic conductance, acoustic
admittance, acoustic compliant reactance, acoustic resistance, acoustic impedance.
Abbreviations: AR = acoustic reflex, ART = acoustic-reflex threshold, ARGF
= acoustic-reflex growth function, BA = acoustic compliant susceptance, GA
= acoustic conductance, YA = acoustic admittance, -XA = acoustic compliant
reactance, RA = acoustic resistance, ZA = acoustic impedance, MANOVA =
multiple analysis of variance, b1 = linear polynomial coefficient,
b2 = quadratic polynomial coefficient, b3 = cubic polynomial coefficient, SEB = standard
error of estimate of the regression coefficient, R2 = the squared multiple correlation, dB SL re: ART = dB sensation level re: the acoustic-reflex threshold.
Sumario:
Se obtuvieron funciones de crecimiento del reflejo acústico (ARGFs) de 20
sujetos con audición normal. Se generaron reflejos acústicos contralaterales
(ARs) con tonos puros a 2000 Hz. La magnitud de los cambios en la compliancia de susceptancia estática (BA) y en la conductancia (GA) se monitorizaron
con sondas de prueba a frecuencias de 226 Hz, 678 Hz y 1000 Hz. Los ARGF
se obtuvieron con seis combinaciones del componente constituido por la frecuencia de la sonda de prueba y la admitancia: 226 Hz BA, 226 Hz GA, 678
Hz BA, 678 Hz GA, 1000 Hz BA y 1000 Hz GA. Los AR obtenidos a conductancia (GA) y susceptancia (BA) pico fueron los mayores dentro de las ARGF
*St. John’s University, Jamaica, N.Y. 11439 and Audiology and Speech Pathology Department, Veterans Affairs New Jersey
Health Care System, East Orange, New Jersey 07018
**Department of Biobehavioral Sciences, Speech-Language Pathology and Audiology Program, Teachers College,
Columbia University, N.Y. 10027
† Department of Speech Communication Arts & Sciences, Brooklyn College, CUNY, Brooklyn, N.Y. 11210
Reprint Requests: John J. Lutolf, Department of Speech, Communication Sciences and Theatre, St. John’s University, 8000
Utopia Parkway, Jamaica, N.Y. 11439.
109
Journal of the American Academy of Audiology/Volume 14, Number 2, 2003
a 678 Hz GA y 1000 Hz BA, respectivamente. Entre los tonos de prueba de alta frecuencia, los patrones de crecimiento del AR fueron mayores y menos variables para los ARGF
a 678 Hz GA y los ARGF a 1000 Hz BA, determinados por la magnitud de sus coeficientes
de polinomio lineal (b1) y de polinomio cuadrático, y por el valor de sus coeficientes de
correlación al cuadrado (R2).
Palabras Clave: Reflejo acústico, función de crecimiento del reflejo acústico, frecuencia
de la sonda de prueba, susceptancia de compliancia acústica, conductancia acústica,
admitancia acústica, reactancia de compliancia acústica, resistencia acústica, impedancia acústica.
Abreviaturas: AR = reflejo Acústico; ART = umbral del reflejo acústico; ARGF = función
de crecimiento del reflejo acústico; BA = susceptancia de compliancia acústica; GA = conductancia acústica; YA = admitancia acústica; -XA= reactancia de compliancia acústica;
RA = resistencia acústica; ZA = impedancia acústica; MANOVA = Análisis de variancia
múltiple; b1 = coeficiente polinomial lineal; b2 = coeficiente polinomial cuadrático; b3 =
coeficiente polinomial cúbico; SEB = error estándar del estimado del coeficiente de regresión; R2 = correlación múltiple al cuadrado; dB SPL re: ART = nivel de sensación en dB
con relación al umbral del reflejo acústico.
H
igh-frequency probe tones of 678 Hz
and 1000 Hz are now available on a
number of immittance meters used
in many clinics, among them, the Grason
Stadler model GSI-33 Version 2 Middle Ear
Analyzer and the, now discontinued, Virtual
model 310 Immitance Meter which is still
being used by many clinicians. While three
studies have addressed the use of a probe
tone of 660 Hz for measuring the ARGF
(Creten, Vanpeperstraete, Van Camp &
Doclo, 1976; Wilson & McBride, 1978; and
Sprague Wiley & Block, 1981), the use of a
probe-tone frequency of 1000 Hz to monitor the
generation of ARGFs has not been investigated.
The present study investigated the peak
magnitude and growth characteristics of
conductance ARGFs and compliant susceptance ARGFs, obtained with a probe tone of
1000 Hz, and compared them with compara-
Table 1 Mean Peak Acoustic-Reflex Magnitude
Probe Tone Frequency
226 Hz
(int.- peak)
Admittance
BA
-.183 # +
(@ 21.4)
GA
-.131 # +
(@ 19.7)
(SD) (% mean)
(SD/ int.- peak)
(.054) (29.5%)
(6.992)
(.056) (42.7%)
(6.165)
678 Hz
(int.- peak)
.346 # + *
(@ 12.1)
-.717 # * ^
(@ 18.2)
(SD) (% mean)
(SD/ int.-peak)
(.298) (86.1 %)
(6.504)
(.365) (50.9%)
(7.281)
1000 Hz
(int.- peak)
1.106 + * ^
(@ 16.8)
.418 # + * ^
(@ 14.0)
(SD) (% Mean)
(.515) (46.5%)
(SD/ int.-peak)
(8.089)
* Sig. diff. from both 226 Hz BA and 226 Hz GA ? = < 0.05
# Sig.diff. from 1000 Hz BA ? = < 0.05
+ Sig diff. from 678 Hz GA ? = < 0.05
^ Sig. diff. from 678 Hz BA ? = < 0.05
(.509) (121%)
(7.650)
Note. The acoustic-reflex activating stimulus = 2000 Hz. Values = mean change in admittance in acoustic millimhos (mmho)
at mean dB SL re: ART. N = 20. BA = compliant susceptance. GA = conductance. SD = standard deviation. int.- peak = intensity in dB SL re: ART at which the peak magnitude of the acoustic reflex was obtained. % mean = SD/mean X 100. SD/int.peak = standard deviation for the int.-peak value.
110
The Effects of Probe-Tone Frequency on the Acoustic-Reflex Growth Function/Lutolf et al
ble measures obtained with probe-tone frequencies of 226 Hz and 678 Hz. The study
sought to contribute to the development of a
normative base for ARGFs obtained with a
probe tone of 1000 Hz. It also sought to
expand upon the findings of prior investigators relative to the characteristics of ARs
obtained with a probe-tone of 660 Hz.
Defining the characteristics of the ARGF
for high-frequency probe tones in normals,
may prove of clinical value because the characteristics of the ARGF obtained with probe
tones of 678 Hz and 1000 Hz may be uniquely altered in the presence of pathological conditions (Sprague, et al., 1981). In addition,
they may be more sensitive to pathological
conditions than their 226 Hz counterpart.
METHOD
Subjects
The subjects for this study were twenty
young males with normal hearing. They
ranged in age from 21 to 41 years (mean =
27.8 yrs). In cases where data from only 16
subjects were analyzed, due to limitations
imposed by the repeated measures design,
the mean age was 28.6 yrs. Air conduction
and bone conduction thresholds were < 15
dB HL at octave frequencies of 250 Hz
through 8000 Hz, except at 4000 Hz where
they were < 20 dB HL. All air conduction
and bone conduction thresholds were within
± 10 dB HL. Tympanometry and peak-pressure function were within normal limits.
Instrumentation
Acoustic-Reflex Activation System
Contralateral acoustic-reflex growth
functions were elicited with 2000 Hz puretones. These activators were generated with
a Tektronix model 501 Function Generator
with a rise/fall time of 25 ms, a duration of 1
s, and an inter-stimulus interval of 4 s. A
stimulus train of 23 presentations was used
to generate each ARGF. The intensity of the
reflex-activating stimulus was presented in
an ascending format from 74 dB SPL to 118
dB SPL in increments of 2 dB SPL. In addition, four silent presentation periods, each
with a duration of 4.9 s, were incorporated in
the stimulus train to facilitate recording of
the AR. These silent periods occurred before
the sixth, eleventh, sixteenth, and twenty-
first stimulus presentations in the ARGF.
The temporal characteristics and the intensity parameters of the acoustic-reflex activating stimuli as well as the silent periods
in the stimulus train were controlled by
logic modules from the Coulbourn model C-1
Modular Instrument System.
Simultaneously with the onset of signal
generation, the Middle Ear Analyzer was
triggered. This input activated the reflexrecording circuit of the GSI-33 Version 2 for
a period of 1000 msec in order to record the
magnitude of the acoustic reflex.
Four silent periods, each of 4.9 s were programmed within each trial. These silent periods occurred before the presentation of the
reflex eliciting stimuli at the following intensity levels: 84 dB SPL, 94 dB SPL, 104 dB
SPL, and 114 dB SPL. These silent periods
were necessary because of constraints in the
reflex-recording program of the Grason
Stadler Model GSI 33 Version 2 Middle Ear
Analyzer. They coincided with the time periods during which the acoustic-reflex recording
circuit of the GSI-33 Version 2 was being reset
to begin a new line on the recording screen.
Acoustic-Reflex Recording System
Changes in static acoustic compliant
susceptance or static acoustic conductance
at the plane of the tympanic membrane
resulting from the AR, were monitored with
probe tones of 226 Hz, 678 Hz and 1000 Hz.
The acoustic-reflex recording system of the
Grason Stadler model 33 Version 2 Middle
Ear Analyzer was used to measure and
record these changes in compliant susceptance and conductance. This recording system permitted generation of ARGFs incorporating six probe-tone frequency/admittance
combinations, namely: 226 Hz BA, 226 Hz
GA, 678 Hz BA, 678 Hz GA, 1000 Hz BA, and
1000 Hz GA. It also provided a display of
these ARGFs in both graphic and digital formats. The order of presentation of each
probe-tone/admittance combination was randomly selected to avoid order effects. Right
and left ears were also counterbalanced.
Graphic and Digital Responses
The reflex recording circuit of the
Grason Stadler GSI-33, Version 2, provided
a graphic recording of the response and a
numerical value equivalent to the peak mag-
111
Journal of the American Academy of Audiology/Volume 14, Number 2, 2003
Table 2. Summary of Average Trend Coefficients (Value in mmho)
226 Hz BA
(SD)
(SE)
(N)
Outliers = 3
Linear
b1
-.0069
(.0024)
(.0014)
(N = 3)
Quadratic
b1
-.0164
(.0036)
(.0013)
(N = 7)
Cubic
b1
.0091
(.0078)
(.0045)
(N = 3)
b2
.0004
(.0001)
(.00006)
b2
-.0027
(.0004)
(.0002)
b3
.00006
(.00004)
(.00002)
Sample Average - 226 Hz BA (N = 16)
Curve fit to Sample ARGF
Average of Sample Quad Coeffs.
Quadratic
Quadratic
b1
b2
b1
b2
.0111
.0002
-.0110
.00020
SD (.0071)
(.00038)
SEB (.0006)
(.00003)
[R2 = .995 (SE = .0034)]
[R2 = .897 (SD = .0886)]
226 Hz GA
(SD)
(SE)
(N)
Outliers = 2
Linear
b1
-.0063
(.0032)
(.0016 )
(N = 4)
Quadratic
b1
.0163
(.0101)
(.0033)
(N = 9)
b2
.0005
(.0003)
(.0001)
Cubic
b1
-.0161
(.0000)
(N = 1)
b2
.0014
(.0000)
-
b3
-.00004
(.0000)
-
Sample Average - 226 Hz GA (N = 16)
Curve fit to Sample ARGF
Average of Sample Quad Coeffs.
Quadratic
Quadratic
b1
b2
b1
b2
-.0124
.0004
-.0124
.00034
SD (.0089)
(.00034)
SEB (.0010) (.00005)
[R2 = .9836 (SE = .0052)]
[R2 = .9071 (SD =.0657)]
Note. SD = standard deviation. SE = standard error of estimate. N = number of subjects. BA = compliant susceptance. GA =
conductance. b1 = linear coefficient. b2 = quadratic coefficient. SEB = standard error of estimate of the regression coefficient.
R2 = squared multiple correlation coefficient.
nitude of the response adjacent to the graphic representation of the acoustic reflex in its
standard recording mode. The reflex recording circuit also permitted a digital read out
of each acoustic reflex response.
Response Criteria
Two criteria were established to determine whether a response was considered an
acoustic reflex. First, the minimum change
in static conductance or compliant susceptance had to equal or exceed the following
values when monitored with the following
probe-tone frequencies:
1. 0.015 mmho for a probe-tone frequency
of 226 Hz,
2. 0.055 mmho for a probe-tone frequency
of 678 Hz. and
3. 0.085 mmho for a probe-tone frequency
of 1000 Hz.
112
(Wilson, 1979; Grason-Stadler, Inc., 1998, p-30).
Second, the magnitude of all subsequent
responses must equal or exceed these minimum values. These minimum threshold values were those suggested by the manufacturer. The stipulation that all subsequent
values in the ARGF meet or exceed those
values was a conservative requirement
imposed by the design of the study to insure
against accepting a random false-positive
change in admittance as a response.
Calibration
Prior to each test session, the reference
intensity levels, the frequency of the probe
tones, and the linearity and the frequency of
the reflex-eliciting 2000 Hz stimuli were calibrated using a Bruel and Kjaer (B&K) type
2235 Precision Sound Level Meter, a B&K
type 1625 1/3-1/1 Octave Filter, A Beckman
The Effects of Probe-Tone Frequency on the Acoustic-Reflex Growth Function/Lutolf et al
Table 3. Summary of Average Trend Coefficients (value in mmho)
678 Hz BA
(SD)
(SE)
(N)
Outliers = 3
Linear
b1
.0322
(.0116)
(.0069)
(N = 3)
Quadratic
b1
.0778
(.0191)
(.0110)
(N = 3)
Cubic
b1
.1117
(.0366)
(.0163)
(N = 5)
b2
-.0032
(.0007)
(.0004)
b2
-.0110
(.0034)
(.0015)
b3
.00032
(.00008)
(.00003)
Sample Average - 678 Hz BA (N = 16)
Curve fit to Sample ARGF
Average of Sample Quad Coeffs.
Quadratic
Quadratic
b1
b2
b1
b2
.0465
-.0018
.0463
-.0018
SD (.0294)
(.0014)
SEB (.0049)
(.0002)
[R2 = .9531 (SE = .0242)]
[R2 = .6796 (SD = .2327)]
678 Hz GA
(SD)
(SE)
(N)
Outliers = 2
Linear
b1
-.0368
(.0277)
(.0138 )
(N = 4)
Quadratic
b1
-.0154
(.0594)
(.0266)
(N = 5)
b2
.0033
(.0021)
(.0009)
Cubic
b1
-.1360
(.0361)
(.0208)
(N = 3)
b2
.0114
(.0030)
(.0017)
b3
-.0003
(.0001)
(.00006)
Sample Average - 678 Hz GA (N = 16)
Curve fit to Sample ARGF
Average of Sample Quad Coeffs.
Quadratic
Quadratic
b1
b2
b1
b2
-.0728
.0019
-.0761
.0021
SD (.0428)
(.0020)
SEB (.0045) (.0002)
[R2 = .9928 (SE = .0224)]
[R2 = .8794 (SD =.1452)]
Note. SD = standard deviation. SE = standard error of estimate. N = number of subjects. BA = compliant susceptance. GA =
conductance. b1 = linear coefficient. b2 = quadratic coefficient. SEB = standard error of estimate of the regression coefficient.
R2 = squared multiple correlation coefficient.
model 6240 Frequency Counter, a Hewlett
Packard model 465-A amplifier, and a B&K
model ASM 2cc Coupler. At the onset of the
study, the probe-tone frequencies were also
evaluated for harmonic distortion. In addition, the manufacturer’s calibration cavities
and the internal calibration program on the
Grason Stadler GSI-33 Version 2 Middle Ear
Analyzer were used to calibrate the middle
ear analyzer before each test session.
A Gilmont model 1200 2.0 Micro-Liter
Syringe was used to verify the volume and
linearity of the equivalent air-volume
changes associated with millimho changes
in the middle-ear static compliance during
reflex contraction.
Statistical Analysis
The peak AR magnitude (in mmho units),
and the intensity level (in dB SL re: ART) at
which the AR with the largest magnitude
occurred were identified from the individual
ARGFs. Mean and standard deviations were
calculated and the data were submitted to
multiple analysis of variance (MANOVA).
The individual ARGFs for each subject
were submitted to an analysis of trend
employing the curve-fitting program available in SPSS for Windows (M.J. Norusis
(1993), p.372). Within a given probe-tone frequency/admittance condition, subjects were
classified according to the linear, quadratic
or cubic polynomial model that provided the
best fit to the data and the largest R2 value.
The individual coefficients and R2 values for each member of a polynomial subgroup, within a given probe-tone frequency/admittance condition, were then averaged
and a mean and standard deviation were
obtained (Table 2, 3 and 4).
The ARGFs for all subjects within a
113
Journal of the American Academy of Audiology/Volume 14, Number 2, 2003
Table 4 Summary of Average Trend Coefficients (Values in mmho)
1000 Hz BA
(SD)
(SE)
(N)
Outliers = 3
Linear
b1
.0549
(.0179)
(.0103)
(N = 3)
Quadratic
b1
.1611
(.0545)
(.0206)
(N = 7)
Cubic
b1
.2523
(.0887)
(.0512)
(N = 3)
b2
-.0055
(.0018)
(.0007)
b2
-.0211
(.0049)
(.0028)
b3
.0005
(.00011)
(.00006)
Sample Average - 1000 Hz BA (N = 16)
Curve fit to Sample ARGF
Average of Sample Quad Coeffs.
Quadratic
Quadratic
b1
b2
b1
b2
.1016
-.0028
.1077
-.0027
SD (.0943)
(.0045)
SEB (.0057)
(.0003)
[R2 = .9939 (SE = .0281)]
[R2 = .8709 (SD = .1389)]
1000 Hz GA
(SD)
(SE)
(N)
Outliers = 2
Linear
b1
.0241
(.0173)
(.0123 )
(N = 2)
Quadratic
b1
.0764
(.0451)
(.0184)
(N = 6)
b2
-.0033
(.0020)
(.0008)
Cubic
b1
-.0314
(.0055)
(.0039)
(N = 2)
b2
.0070
(.0002)
(.000157)
b3
-.0002
(.0000)
(.0000)
Sample Average - 1000 Hz GA (N = 16)
Curve fit to Sample ARGF
Average of Sample Quad Coeffs.
Quadratic
Quadratic
b1
b2
b1
b2
.0423
-.0014
.0422
-.0013
SD (.0532)
(.0027)
SEB (.0049) (.0002)
[R2 = .9603 (SE = .0244)]
[R2 = .6978 (SD =.2503)]
Note. SD = standard deviation. SE = standard error of estimate. N = number of subjects. BA = compliant susceptance. GA =
conductance. b1 = linear coefficient. b2 = quadratic coefficient. SEB = standard error of estimate of the regression coefficient.
R2 = squared multiple correlation coefficient.
given probe-tone frequency/admittance condition were averaged and the polynomial model
which best fit the average ARGF, as determined by significance level and R2 value, was
identified. This was invariably a quadratic
trend (Table 2, 3 and 4).
Finally, as with the subgroups, the coefficients from the individual quadratic models
for all 16 subjects were averaged. A polynomial model was generated which contained
mean b1 and b2 coefficients and a mean R2
value as well as the standard deviations associated with those measures. The coefficients of
these polynomial models were used as a measure of average slope.
RESULTS
Peak Acoustic Reflex Magnitude
The mean peak acoustic-reflex magni-
114
tudes obtained with the six combinations
of probe-tone frequency/admittance component for the twenty subjects are listed
in Table I. The peak magnitudes of the
ARs for 226 Hz B A and 226 Hz G A were
not significantly different. Peak conductance ARs assessed with a probe tone of
678 Hz were approximately five times
larger than the peak conductance ARs for
226 Hz and twice as large as peak conductance ARs monitored with a probetone frequency of 1000 Hz. Conversely,
peak compliant susceptance ARs monitored with a probe tone of 1000 Hz were
approximately six times larger than
those monitored with a probe tone of 226
Hz and three times larger than those
assessed with a probe-tone frequency of
678 Hz. In addition, they showed a rapid
growth rate within 10 dB SL re: ART
(Fig. 1).
The Effects of Probe-Tone Frequency on the Acoustic-Reflex Growth Function/Lutolf et al
Acoustic-Reflex Growth Function
The mean ARGFs for all six experimental conditions were best fit with a quadratic
polynomial model (Figure 1, Table 2, 3 and
4). The smaller rates of growth, as defined
by the mean b1 coefficient, were associated
with the 226 Hz BA and 226 GAA ARGFs.
The growth of compliant susceptance (BA)
ARGFs was larger than the growth of conductance (GA) ARGFS for the probe tone of
1000 Hz. The reverse was true for a probetone frequency of 678 Hz. The
678 Hz BA
ARGFs and the 1000 Hz GA ARGFs were
characterized by extremely high variability
and have no potential for clinical applications (Table 3 and 4).
The average rate of growth for 1000 Hz
BA ARGFs was approximately ten times
larger than that of the 226 Hz BA ARGFs
.The mean deceleration in growth, as indicated by the absolute value of the mean b2
coefficient, was thirteen times larger for the
1000 Hz ARGFs than the 226 Hz BA ARGFs
(Table 2 and 4). The mean slope of the conductance ARGFs monitored with a probe
tone of 678 Hz was approximately six-fold
larger than that for the 226 Hz GA ARGFs.
The average deceleration in growth was also
approximately six-times larger for the 678
Hz GA ARGFs (Table 2 and 3).
DISCUSSION
Acoustic Reflex Magnitude
The peak 678 Hz GA AR magnitudes for
eleven subjects were recorded at the highest
available SPL of the reflex eliciting stimulus.
Therefore, these reflect maximum AR magnitudes rather than peak AR magnitudes
which may have been obtained at > 118 dB
SPL. This same characteristic of the data
was also noted in the other five probe-tone
frequency/admittance conditions but for a
smaller number of subjects in each group.
Peak conductance ARs assessed with a
probe tone of 678 Hz were approximately six
times larger than the peak conductance ARs
for 226 Hz and twice as large as peak conductance ARs monitored with a probe-tone
frequency of 1000 Hz (Table 1). A probe-tone
frequency of 678 Hz approaches a middle ear
resonance for many subjects. As such this
probe-tone frequency will be more sensitive
to changes in middle-ear acoustic resist-
Figure 1. Mean acoustic reflex-growth functions
(ARGFs) for six probe-tone frequency/admittance conditions. Each point is based on 16 observations from 16 subjects. Note. BA =compliant susceptance. GA = conductance. dB SL = dB Sensation Level re: acoustic reflex
threshold.
ance/conductance which accompany the AR
than will probe-tone frequencies of 226 Hz
or 1000 Hz (Moller, 1961, 1964; Bennett &
Weatherby 1979; Bennett, 1984). This factor
may explain the larger peak conductance
ARs obtained with a probe tone of 678 Hz.
The peak compliant susceptance ARs
monitored with a probe tone of 1000 Hz were
approximately six times larger than those
monitored with a probe tone of 226 Hz and
three times larger than those assessed with
a probe-tone frequency of 678 Hz (Table 1).
These findings are in agreement with
those of Bennett & Weatherby (1979) who
reported median values for changes in static
compliant reactance when ARs for BBN
were obtained at 10 dB SL re: ART. These
values were 2.7 acoustic ohms for a probetone frequency of 700 Hz and -0.1 acoustic
ohms for a probe tone of 1000 Hz.
These results may be explained in part
by the findings of Moller (1964) who
observed that the AR was accompanied by a
decrease in the static impedance when monitored with a probe tones above 900 Hz.
Moller (1961) also noted that the middle-ear
resonance near 800 Hz was abolished by the
presence of an acoustic reflex. However, the
higher middle-ear resonance at 1200 Hz was
unaffected by acoustic-reflex contraction.
The variability associated with measures
of peak AR magnitude was high. When the
standard deviation was expressed as a percent of the mean (SD/mean x 100), the smallest variability was observed for the 226 Hz
BA and 226 Hz GA Peak ARs (29.5% and
42.7% respectively) (Table 1). The variability
for 678 Hz GA and 1000 BA peak ARs approximated 50% while that for their 678 Hz BA
and 1000 Hz GA counterparts exceeded 85%.
115
Journal of the American Academy of Audiology/Volume 14, Number 2, 2003
Figure 2.
(a) 678 Hz GA acoustic-reflex growth functions (ARGFs)
for subjects, 1-8.
Figure 3.
(a) 1000 Hz BA acoustic-reflex growth functions (ARGFs)
for subjects, 1-8. (b)
(b) 678 Hz GA ARGFs for subjects 9-16. . GA = conductance.
1000 Hz BA ARGFs for subjects 9-16. BA = compliant
susceptance.
Acoustic-Reflex Growth Function
GA ARGFs of fifteen of sixteen subjects
(93.7%) which contained a total of 149
biphasic ARs (mean = 9.3). By comparison,
biphasic ARs were noted in the 1000 Hz BA
ARGFs of seven of sixteen subjects (43.7%),
for which a total of 45 biphasic ARs (mean =
6.4) were observed.
The largest change in static admittance
within a biphasic response, whether positive
or negative, was recorded as the value of the
AR at a given intensity increment within the
ARGF. It is therefore possible that higher
incidence of biphasic ARs may have contributed to the greater variability identified
in the growth patterns of the 678 Hz BA and
1000 Hz GA ARGFs. The presence of multiphasic ARs was offered as an explanation by
Wilson & McBride (1978) for the restricted
pattern of growth observed in their mean
660 Hz ARGF.
Variability
In general, large inter-subject variability seems an unavoidable feature of the
ARGF (Silman, et al., 1978; Wilson, 1979,
1981; Silman & Gelfand (1981); Sprague et
al., 1981). Although data from the present
study suggest that the 678 Hz GA ARGF and
the 1000 Hz BA ARGF were accompanied by
smaller inter-subject variability than their
counterpart 678 Hz Bv and 1000 Hz Gv
ARGFs (Tables: 2, 3 and 4), nevertheless, the
relatively better variability associated wth
the 678 Hz GA and 1000 Hz BA ARGFs still
exceeds that which would be permissible for
clinical applications.
It is interesting to note that biphasic
responses were recorded in the 678 Hz BA
ARGFs of fifteen subjects (93.7%) who
reported a total of 118 biphasic ARs (mean =
7.8). Conversely, biphasic ARs were noted in
the 678 Hz GA ARGFs of six of sixteen subjects (37.5%) for whom a total of 43 biphasic
ARs were observed (mean = 7.2). Biphasic
AR responses were also noted in the l000 Hz
116
Probe-Tone Frequency/Admittance
Effects
A small difference was noted between
the slopes of the 226 Hz BA and the 226 Hz
GA ARGFs. Variability was also similar, as
The Effects of Probe-Tone Frequency on the Acoustic-Reflex Growth Function/Lutolf et al
indicated by the measures of standard deviation and standard error (Table 2). However,
interaction effects were noted between the
probe-tone frequency and the admittance
component when compliant susceptance
ARGFs and conductance ARGFs were
obtained with probe-tone frequencies of 678
Hz and 1000 Hz.
The steepest slope of initial growth for
compliant susceptance ARGFs and the
largest subsequent deceleration in their pattern of growth was observed for ARGFs
obtained with a probe-tone frequency of 1000
Hz (Table 4), (Figure 3). These relationships
are similar to those observed in the peak AR
magnitude and are consistent with the fact
that growth in the magnitude of the compliant susceptance AR is proportional to the
probe-tone frequency (Moller, 1961,1964).
In contrast to the compliant susceptance
ARGF, the growth of the conductance ARGF
was largest when monitored with a probetone frequency of 678 Hz (Table 3), (Figure.
1). The findings regarding the growth of the
conductance ARGF mirror those for peak AR
magnitude measures and are compatible
with prior studies showing that the middleear transmission system is conductance
/resistance dominated in the probe-tone frequency region of 678 Hz (Moller, 1961, 1964;
Creten, et al., 1976; Wilson & McBride, 1978;
Sprague, et al., 1981)).
The data suggest that a probe-tone frequency of 678 Hz is better for monitoring the
growth of conductance (GA) ARs while a
probe-tone frequency of 1000 Hz is preferable for monitoring the growth of the susceptance (BA) AR. In both cases, the growth
characteristics are larger and the variability, as defined by measures of standard deviation and standard error is smaller for these
probe-tone frequency/admittance conditions.
However, the magnitude of variability associated with these measures is unacceptable
for clinical applications.
CONCLUSION
Peak AR
The 678 Hz GA peak AR were approximately five times larger than peak 226 GA
AR and twice as large as the peak 1000 Hz
GA AR. Conversely, the 1000 Hz BA peak AR
was six times larger than the 226 Hz BA
peak AR and three times larger than the 678
Hz BA AR. The 678 Hz GA and 1000 Hz BA
peak ARs have greater potential for diagnostic applications. However, at present, they
are far too variable for clinical use
ARGF
The 1000 Hz BA ARGF and the 678 Hz
GA ARGF had the steepest pattern of growth
(as indicated by the b1 coefficient) and the
largest deceleration in growth (as indicated
by the b2 coefficient). Among the higher frequencies, the 1000 Hz BA and 678 Hz GA
probe-tone frequency/admittance combinations provided ARGFs with less variability.
However, the degree of variability was too
large to encourage clinical application of
these measures at the present time.
Acknowledgment: We wish to thank Drs. Jane Monroe
and David Krantz of Columbia University for their assistance with statistical analysis. We also wish to thank Mr.
Edward Yeung, Graduate Center City University of New
York for assistance with equipment design and programming. A note of appreciation is also extended to Mr.
Charles “Chuck” Comitto, Northeastern Technologies
Corporation, Mr. Robert Guinta, R&R Guinta Associates,
and Mr. Randy Veillette, Nicolet-Grason Stadler
Corporation for their help with equipment and modifications. We also wish to express our gratitude to the reviewers for their constructive comments and valuable suggestions. The data reported are partially based upon the
Ph.D. dissertation of the lead author under the sponsorship of Prof. Honor O’Malley, Columbia University and
the guidance of Shlomo Silman, Ph.D. (Lutolf, 1996). The
study was made possible by the generosity of Mr.
Sigmond K. Schwartz through the Dr. Joanne Schwartz
Memorial Scholarship Fund.
REFERENCES
Bennett MJ & Weatherby LA. (1979). Multiple probe frequency acoustic reflex measurements. Scandinavian
Audiology, 8, 233-239.
Bennett MJ. (1984). Impedance concepts relating to the
acoustic reflex. In S. Silman ed. The Acoustic Reflex: Basic
Principles and Clinical Applications. New York: Academic
Press, (pp. 35-61).
Creten WL, Vanpeperstraete PM, Van Camp KJ & Doclo JR.
(1976). An experimental study on diphasic acoustic reflex patterns in normal ears. Scand Audiol 5:3-8.
Grason-Stadler Inc. (1998). Grason-Stadler GSI 33, Version 2
Middle Ear Analyzer: Instruction Manual 1733-0120, Rev.5.
Milford, New Hampshire.
Moller AR. (1961). Network model of the middle ear. J Acoust
Soc Am 33:168-176.
Moller AR. (1964). The acoustic impedance in experimental
117
Journal of the American Academy of Audiology/Volume 14, Number 2, 2003
studies on the middle ear. Internat Audiol 3:1-13.
Silman S, Popelka GR & Gelfand SA. (1978). Effect of sensorineural hearing loss on acoustic stapedius reflex growth
functions. J Acoust Soc Am 64:1406-1410.
Silman S & Gelfand SA. (1981). The relationship between
magnitude of hearing loss and acoustic reflex thresholds. J.
Speech Hear Disord 46:312-316.
Sprague BA, Wiley TA & Block MA. (1981). Dynamics of
acoustic reflex growth. Audiol 20:15-40.
Wilson RH & McBride LM. (1978). Threshold and growth of
the acosutic reflex. J Acoust Soc Am 63:147-154.
Wilson RH. (1979). Factors influencing the acoustic immittance characteristics of the acoustic reflex. J Speech Hear Res
22:480-489.
Wilson RH. (1981). The effects of aging on the magnitude of
the acoustic refkex. J Speech Hear Res 24:406-413.
118