S 2;1,~ ~? ,
J Am Acad Audiol 9 : 227-233 (1998)
Reliability Issues with the Synthetic
Sentence Identification Test
Kenneth C. Pugh*
Carl C. Crandell*
Scott K. Griffiths*
Abstract
This investigation examined the reliability of the Synthetic Sentence Identification (SSI) test .
An adaptive procedure was used to assess speech recognition thresholds (SRTs) for the SSI
lists over two separate test sessions . The commercially available Davy Crockett passage
and a multitalker babble were used as competition . Subjects consisted of 20 adults with
normal hearing sensitivity. Results indicated (1) significantly higher SRTs with the multitalker
babble, (2) significant differences in SRTs among SSI lists when using the Davy Crockett
competition, (3) no significant learning/practice or fatigue effects across trials in either noise
condition, and (4) high test-retest reliability across test sessions . Clinical implications of these
data are considered .
Key Words: Adaptive procedure, Davy Crockett passage, multitalker babble, reversal,
synthetic sentence identification
Abbreviations: SRT = speech recognition threshold, SSI =synthetic sentence identification,
SSI-ICIVI = synthetic sentence identification-ipsilateral competing message
he Synthetic Sentence Identification
(SSI) test developed by Speaks and
T Jerger (1965) is a well-recognized assessment procedure for the detection of central auditory nervous system lesions (Jerger and Jerger,
1975; Toscher and Rupp, 1978; Hayes and Jerger,
1979a; Cacace et al, 1984 ; Rodriguez et al, 1990 ;
Cooper and Gates, 1991, 1992 ; Fire et al, 1991 ;
Lew and Jerger, 1991 ; Marvel et al, 1992 ; Willeford and Burleigh, 1994). In addition, the SSI test
has been suggested for comparing differences in
performance between hearing aids (Hayes and
Jerger, 1979b; Kricos et al, 1987 ; Del-Dot et al,
1992) and assessing communicative efficiency
(Jerger and Hayes, 1976 ; Orchik and Roddy,
1980). Despite the widespread clinical use of
the SSI, a paucity of literature concerning the
reliability of the test remains, particularly in the
*Department of Communication Sciences and Disorders, Institute for the Advanced Study of Communication
Processes, University of Florida, Gainesville, Florida
Reprint requests : Kenneth C . Pugh, Institute for the
Advanced~Study of Communication Processes, 63 Dauer
Hall, P.O . Box 117425, University of Florida, Gainesville, FL
32611-7425 ; Tel : (352) 392-2113 ; Fax : (352) 846-0243
presence of the commercially available Davy
Crockett competing message.
The limited number of investigations examining the reliability of SSI test scores typically
have addressed learning/practice or fatigue
effects (Speaks and Jerger, 1965 ; Speaks et al,
1966 ; Speaks, 1967 ; Jerger et al, 1968 ; Beattie
and Clark, 1982 ; Dubno and Dirks, 1983) . The
majority of these investigations used subjects
with normal hearing sensitivity and low-pass filtered stimuli. For example, Speaks and Jerger
(1965) presented low-pass filtered SSI sentences
in quiet to six listeners with normal hearing.
Results indicated that learning effects could be
diminished by presenting 100 practice sentences
prior to test administration . In a similar investigation, Speaks et al (1966) used four individuals with normal hearing sensitivity and
reported that approximately 40 to 60 practice SSI
sentences were required to reduce learning
effects. Speaks (1967) indicated that two practice trials (20 sentences) were needed to decrease
practice effects in three normal hearers listening to low-pass filtered SSI sentences. Jerger et
al (1968) examined the learning effects of the SSI
test in the presence of a continuous discourse
(Davy Crockett passage) . Results indicated the
227
Journal of the American Academy of Audiology/Volume 9, Number 3, June 1998
learning effects were reduced when a minimum
of 30 practice sentences were presented. Beattie and Clark (1982) used a four-talker babble
to examine the practice effects on SSI performance. Subjects consisted of 16 normal hearers.
Results indicated that approximately 60 practice sentences were required before stable SSI
scores were obtained . Dubno and Dirks (1983)
investigated the reliability of the SSI for 33 subjects with mild-to-moderate degrees of sensorineural hearing loss . The SSI sentences were
presented in a background of cafeteria noise.
Data from this investigation indicated that a
minimum of 30 sentences were required to
reduce learning effects. In addition, results indicated that (1) practice trials should be administered only under relatively difficult listening
conditions, (2) practice trials should occur at
the beginning of each new testing session, and
(3) adaptive speech-recognition procedures
should be employed to assess SSI scores .
Although the aforementioned investigations
suggest that approximately 20 to 100 practice
sentences are required to reduce learning effects
in the SSI test, several methodological questions can be raised . First, a majority of previous
investigations examined SSI performance only
in quiet and/or low-pass filtered listening conditions (Speaks and Jerger, 1965 ; Speaks et al,
1966 ; Speaks 1967 ; Jerger et al, 1968). Typically, the SSI test is not administered in these
listening conditions within the clinical setting.
Only one investigation has addressed reliability issues in the SSI test using the commercially available Davy Crockett competition
(Jerger et al, 1968). Second, each of the previous investigations has used percent-correct
recognition procedures to assess learning effects.
It is well recognized that percent-correct procedures exhibit a number of potential difficulties,
including high intra- and intersubject variability and floor/ceiling effects (Plomp, 1986 ; Crandell, 1991 ; Crandell and Boney, 1998). Third, a
relatively small number of subjects were used
in past investigations to determine learning/practice effects . For example, Speaks (1967) and
Speaks and Jerger (1965) used only three and
six subjects, respectively.
In the-present investigation, the reliability
of the SSI test scores was examined both in the
presence of the commercially available Davy
Crockett passage and in the presence of multitalker babble . Inasmuch as the SSI test is commonly used to rule out central auditory processing disorder in listeners with normal hearing
sensitivity (Katz et al, 1992), adults with normal
228
hearing sensitivity served as subjects for this
investigation . To avoid difficulties with
percent-correct scores, an adaptive speechrecognition procedure was used to estimate 50
percent-correct performance level (Levitt and
Rabiner, 1967 ; Levitt, 1971 ; Plomp and Mimpen,
1979) . Adaptive procedures are employed to
avoid many of the problems inherent in traditional speech-recognition testing approaches .
Specifically, adaptive procedures are more sensitive in evaluating perceptual difficulties, provide estimates of subject reliability during a
single test administration, and avoid floor and
ceiling effects (Crandell, 1991 ; Crandell and
Boney, 1998) .
METHOD
Subjects
Twenty adult listeners (14 females, 6 males)
with normal hearing sensitivity served as subjects for this investigation . Subjects ranged from
18 years to 40 years of age, with a mean age of
24 years. All subjects met the following criteria :
(1) bilateral pure-tone air-conduction thresholds no poorer than 15 dB HL from 250 Hz to
8000 Hz in octave intervals, with no significant
air-bone gap (>10 dB) at any frequency; (2)
middle ear function within normal limits bilaterally, as indicated by tympanometry (+150
daPa); (3) English as a first language as reported
by the subject; (4) no prior experience with the
SSI test ; (5) no significant medical problems as
reported by the subject; and (6) absence of central auditory difficulties or speech perception difficulties in noise as reported by the subject.
Speech Stimuli
The SSI test was used to assess sentence
recognition . The SSI test consists of 10 sevenword sentences presented in a closed-set, continual discourse format . The sentences are
spoken by a male speaker with a general American dialect and no obvious speech anomalies
(Speaks and Jerger, 1965). A closed-set format
is used to reduce subject dependence on linguistic processing. Words for the SSI test were
selected from the Thorndike and Lorge (1944) list
of the 1000 most familiar words in the English
language . Synthetic sentence word sequence is
based on third-order approximations to English sentences, in that the third word of each sentence is dependent on the preceding first and
second words (Speaks and Jerger, 1965).
SSI Reliability/Pugh et al
A compact disc version containing nine different randomizations of the 10 SS1 lists is commercially available from the Department of
Veterans Affairs . The nine SSI lists are located
on tracks 27 to 35 . This version of the SSI test
was used in this investigation. A silent period of
approximately 7 seconds occurs between each
synthetic sentence to allow for the identification
task . The compact disc includes a 1000-Hz calibration tone equal to the root-mean-square
amplitude of all speech stimuli.
Competing Message Stimuli
Both the Davy Crockett passage and multitalker babble were used as noise competition.
The Davy Crockett passage is a chronicle of the
life and daily events of Davy Crockett . This
recorded dialogue is spoken by the same speaker
of the synthetic sentences (Jerger et al, 1968) .
At present, the Davy Crockett passage is the
most common commercially available competition for the SSI sentence lists and is also included
on the compact disc version of the SSI test .
The multitalker babble recording, provided
by Auditec of St. Louis, was generated by recording six adults (three males/three females) reading a passage in an anechoic chamber. The six
recordings were then combined with a second
recording of the same speakers, producing a 12speaker babble . A 1000-Hz calibration tone equal
to the root-mean-square amplitude of the multitalker babble is included on the high-quality
recorded cassette tape . This competition was
chosen for two reasons. First, multitalker babble exhibits minimal temporal cues associated
with connected discourse, which may serve
to facilitate identification . Second, multitalker
babble was chosen as an additional noise competitor because its spectral shape is similar to
the background noises commonly encountered
in "everyday" listening situations (Crandell,
1991).
Procedure
All testing was completed in a double-walled
sound-treated booth (IAC Model 403-A) . The
SSI stimuli were played on a Teac (Model PD80) compact disc player, routed through a Virtual (Model 320) audiometer, and presented via
TDH-49 earphones mounted in MX-41/AR supraaural cushions . All stimuli were routed to the
right ear of each subject. The Davy Crockett
competition was presented to each subject via the
second track of the compact disc in the same fash-
ion as the SSI sentences. The multitalker babble,
presented via high-quality recording tape, was
routed through a Realistic (Model SCT-24A)
tape recorder, through a Virtual (Model 320)
audiometer, and both forms of competition were
presented to the right ear of each subject. All subjects were given a hard copy numbered list of the
10 SSI sentences . Each subject's task was to
correctly identify the sentence by verbalizing
the corresponding number of the sentence .
An adaptive procedure described by Levitt
and Rabiner (1967) and modified by Plomp and
Mimpen (1979) was used to estimate the speechrecognition threshold (SRT) or 50 percent-correct performance level for the SSI sentences.
The following procedure was used to assess the
SRT:
1.
2.
3.
4.
Presentation of the first sentence began at
an inaudible level and was increased in 2dB steps until a synthetic sentence was
properly identified . Subjects were encouraged to guess when necessary.
The ensuing synthetic sentence on the list
was then presented at a level 2 dB lower
than the previous sentence .
If the ensuing synthetic sentence was correctly recognized, then the presentation
level for the third synthetic sentence was further decreased by 2 dB . If, however, the second synthetic sentence was not correctly
recognized, then presentation level was
increased by 2 dB for the third synthetic sentence.
The above steps were repeated for all synthetic sentences.
Aminimum of three reversals was required
for each trial . If three reversals were not
obtained, the SRT was not assessed for that
specific trial. Overall, 92 .2 percent of the trials
(332 trials of a total 360 trials) in Davy Crockett passage noise condition and 100 percent of
the trials (360 trials of a total 360 trials) in the
multitalker babble noise condition exhibited
three or more reversals (mean = five reversals
per list). Because of the enhancement of sensitivity and specificity in tests of central auditory
dysfunction obtained at higher presentation levels (Katz et al, 1992 ; Willeford and Burleigh,
1994), competing message stimuli were presented to the same ear as the SSI sentences
(SSI-ICM) and remained at a constant level of
80 dB HL .
A total of 36 trials were presented to each
subject over two separate test sessions sepa229
Journal of the American Academy of Audiology/Volume 9, Number 3, June 1998
rated by at least 3 days . Each test session consisted of 18 trials where either the Davy Crockett passage or the multitalker babble was used
as the competition. Within the 18 trials, the
nine different SSI lists were randomly assigned
so that each list was presented twice to each subject . To ensure subject attentiveness, frequent
breaks (approximately every 15 minutes) were
permitted within each test session.
Statistical Analyses
Analysis of variance (ANOVA) and Pearson
product-moment correlation procedures were
used to measure the effect of the categorical
variables (i .e ., nine separate SSI lists, two types
of competition, and two repetitions for a total 36
trials) on SSI scores . Analyses were carried out
using the Statistical Application Software (SAS
version 6.11) program. In each analysis, the criterion (alpha level) of p < .01 was used for judging statistical significance .
RESULTS
T
he mean SRTs for the SSI lists in the presence of both the commercially available
Davy Crockett passage and the multitalker
babble listening conditions are presented in
Figure 1 . Error bars indicate -1 standard error
of the mean. Repeated measures ANOVA indicated that the multitalker babble condition made
it significantly more difficult for subjects to identify synthetic sentences (F = 32 .39; df = 1, 19 ;
p = .0001) . That is, subjects obtained
significantly higher SRTs with the multitalker
babble (average SRT = 66 .24 dB) than with
the Davy Crockett competition (average SRT =
46 .35 dB).
10
Davy Crockett Passage
® Multitalker Babble
0
z
-20
-30
-40
ir
Figure 1 Mean SSI SRT scores (in dB SIN) in each noise
condition.
230
SSI List
Number
1
2
3
4
5
6
7
8
9
Davy Crockett
Passage
Multitalker
Babble
Mean
SD
Mean
SD
-33 .43
8 .82
-13 .87
7 .85
11 .63
9 .38
7 .79
-13 .24
-13 .83
-12 .94
6 .60
7 .96
7 .03
-13 .34
-12 .51
8 .52
3 .58
-35.56
-32.63
9.08
13 .97
-37.67
9 .56
-34 .06
-35 .26
-32 .69
-37 .08
-20 .92
9 .27
5 .75
-13.74
-12 .76
-14 .20
8.49
6.67
7.62
Table 1 illustrates SRT scores and standard deviations across the various SSI lists .
These data are collapsed across the 18 trials
for each noise condition. Analysis of variance
indicated nonsignificant differences in SRT
scores across lists with the multitalker babble
(F = 1.34; df = 8, 19 ; p = .23) . Conversely, significant differences were observed in SRT scores
across lists with the commercially available
Davy Crockett passage (F = 69 .20 ; df = 8, 19 ;
p = .0001) .
Post hoc pairwise comparisons using the
Tukey Multiple Comparison Test indicated that
Table 2 Mean SSI SRT Scores (in dB S/N)
across Trials in the Presence of Noise at
80 dB HL (Collapsed across Lists)
Davy Crockett
Passage
SSI Trial
Number
Mean
SD
1
-29 .50
11 .30
3
-32 .10
11 .25
2
4
-10
U)
Table 1 Mean SSI SRT Scores (in dB S/N)
across Lists in the Presence of Noise at
80 dB HL (Collapsed across Trials)
5
6
7
8
9
10
11
12
13
14
15
16
17
18
-31 .20
-31 .21
-28 .68
-33 .29
-32 .82
-29 .85
-34 .36
-39 .15
-35 .85
-39 .98
-40 .10
-37 .97
-36 .03
-36 .01
-37.66
-32 .46
Multitalker
Babble
Mean
SD
-9 .60
0 .82
-11 .22
0 .73
11 .75
-11 .56
12 .86
-11 .09
11 .93
11 .39
11 .86
11 .89
11 .02
2 .36
8 .93
1 .37
2 .20
2 .47
7 .21
6 .53
1 .77
7 .17
1 .85
1 .59
-10 .67
-11 .07
-10 .89
-10 .78
-11 .67
-13 .68
-13 .42
-14 .99
-15 .63
-13 .40
-15 .50
-15 .37
0 .65
1 .38
1 .49
1 .34
1 .19
10 .43
6 .20
8 .25
8 .68
7 .97
9 .97
9 .00
-15 .13
9 .91
-12.78
4 .39
SSI Reliability/Pugh et al
co
z
Davy Crockett Passage
Multitalker Babble
Figure 2 Test-retest repeatability of mean SRT scores
(in dB SIN) across test sessions .
list 9 (mean SRT = 59 .08) produced a significantly different SRT than each of the remaining
SSI lists in the Davy Crockett condition. In addition, post hoc analyses indicated that list 3
(mean SRT = 47 .37) was significantly different
from lists 9, 8, and 7. Conversely, in the multitalker babble noise condition, no significant
differences were obtained across SSI lists.
Table 2 illustrates the SRTs and standard
deviations across trials (i .e., learning/practice and
fatigue effects) . These data are collapsed across
the nine separate randomizations of synthetic
sentence lists . With the adaptive procedure,
administration of the SSI test produced no significant evidence of learning/practice or fatigue
effects across repeated trials in either noise
condition (Davy Crockett passage: F = 0 .94;
df = 16,18; p = .53; multitalker babble : F = 1 .35;
df = 16,18; p = .17) .
SRTs were also compared across test sessions to assess test-retest reliability (Fig. 2) .
Pearson product-moment correlation coefficients
revealed a highly significant relation between
SRT scores obtained in the first and second test
sessions (Davy Crockett passage: r = 0.98, p =
.0001; multitalker babble : r = 0.97, p = .0001) .
DISCUSSION
he present investigation examined reliabilT ity of SSI test scores using an adaptive procedure . SRTs were obtained from 20 adults with
normal-hearing sensitivity and no prior SSI
experience . Results indicated the following: (1)
significanntly higher SRTs with the multitalker
babble, (2) significant differences in SRTs among
SSI lists when using the Davy Crockett compe-
tition, (3) no significant learning/practice or
fatigue effects across trials in either noise condition, and (4) high test-retest reliability across
test sessions in both noise conditions .
The use of multitalker babble greatly influenced SRTs on the SSI test . In order for subjects
to correctly identify synthetic sentences in the
multitalker babble condition, elevated presentation levels were required (multit.Alker babble
SRT = 66 .24 dB ; Davy Crockett passage SRT =
46 .35 dB). This finding was expected as multitalker babble, more so than the Davy Crockett competition, reduces the acoustic/linguistic
redundancy of the message, which makes recognition of speech more difficult. Conversely, the
Davy Crockett competition allows for increased
acoustic/linguistic redundancy as it contains a
number of temporal gaps or periods of reduced
amplitude. The observed differences in SRTs
across noise conditions would suggest that gaps
contained within the connected discourse served
to facilitate identification .
A similar conclusion was reported by Martin and Mussell (1979), who examined the effects
of speech noise and the Davy Crockett discourse
on SSI scores in 30 subjects with normal hearing sensitivity. Results of their investigation
indicated that pauses in the Davy Crockett discourse enabled correct identification of synthetic
sentences solely on the intelligibility of a single
word heard within the sentence . Martin and
Mussell (1979) suggested that a clinically useful alternative for SSI administration would be
the use of a combined Davy Crockett passage and
speech noise competitor, which would serve to
eliminate the pauses while preserving the subject's perception of continuous discourse. This
modification in diagnostic application of the SSI
test would make the task of identifying synthetic sentences more difficult (i .e ., would result
in elevated SRTs), but should serve to minimize
interlist differences . The authors of the present
study are currently investigating the clinical
implementation of this procedure.
With the commercially available Davy
Crockett passage, there was a significant effect
in SRTs across SSI lists. It was revealed that list
9 produced the most significant difference (average SRT = 59 .08), indicating that it was more difficult to identify than the remaining SSI lists.
List 3 (average SRT = 47 .37) was also significantly different than lists 9, 8, and 7. These
results suggest that portions of the Davy Crockett continuous discourse that coincide with these
two lists possibly contain different temporal/spectral energy patterns than portions coinciding
231
Journal of the American Academy of Audiology/Volume 9, Number 3, June 1998
with the other SSI lists. These findings make
questionable the clinical use of lists 3 and 9
(SSI tracks 29 and 35) on the compact disc, as
the observed differences across SSI lists could
influence clinical test results . For example, a
score obtained during administration of the commercially available SSI test may not represent
a reliable measure of central auditory processing when the two SSI lists in question are used .
This issue warrants further investigation. Conversely, recall that using the SSI test with
a noise competition such as the multitalker
babble eliminated these interlist differences .
It is important to note that the authors are
not necessarily recommending clinical use of
multitalker babble in place of the commercially
available Davy Crockett passage . Instead, the
authors are suggesting a need to develop competition materials such as those recommended
by Martin and Mussell (1979) that could aid in
increasing the overall reliability of the obtained
SSI score . An important consideration in the
creation of any new competition is the maintenance of a perceivable continuous discourse,
which must be disregarded in order to perceive
the synthetic sentence . If new competition materials were to lose their discourse quality, the
utility of the SSI test in assessment of central
auditory processing skills would be suspect.
Using the SSI test in either noise condition
resulted in no significant learning/practice or
fatigue effects. These findings run contrary to
previous investigations of the SSI test, where
learning/practice effects were noted to persist
over 20 to 100 trials (Speaks and Jerger, 1965 ;
Speaks et al, 1966 ; Speaks, 1967 ; Jerger et al,
1968 ; Beattie and Clark, 1982 ; Dubno and Dirks,
1983). Possible reasons for this discrepancy may
include the adaptive procedure, the larger number of subjects, or the obscuring effect of collapsing across SSI lists in the Davy Crockett
noise condition (for which there were significant list differences) . Whether this finding holds
true for hearing-impaired persons remains to be
seen, although the data from Dubno and Dirks
(1983) would suggest that subjects with hearing
impairments do not require a greater number of
practice trials than subjects with normal hearing sensitivity.
Finally, the test-retest reliability of the SSI
test using an adaptive procedure was quite high .
Previous investigations of the SSI test that have
used percent-correct procedures have not
reported test-retest reliability. Although it
remains uncertain whether the adaptive procedure influenced this finding, the methodology
232
used in this investigation provided high interand intrasession reliability.
Considering the results of this investigation, the authors offer the following recommendations for clinical use of SSI test materials.
First, a clinically useful alternative for SSI
administration could be to combine the Davy
Crockett passage with an additional noise or
use of an alternate noise competitor. As indicated
by Martin and Mussell (1979), this clinical modification would serve to fill the temporal gaps
while preserving the subject's perception of continuous discourse. The authors concur with this
recommendation and are presently investigating its clinical implementation . Second, if the SSI
test is administered in its most commercially
available format, then it should be recognized
that list differences may exist, which could have
an effect on test results. Third, if competing
noise materials such as the commercially available Davy Crockett passage or an alternate
noise competitor are used, along with an adaptive procedure, then practice lists may not be
required . Finally, recall that this investigation
used subjects with normal hearing sensitivity;
thus, any implications extrapolated from these
data apply only to this population . However, it
must also be stated that persons with central
auditory processing difficulties typically exhibit
normal hearing sensitivity (Katz et al, 1992).
These data suggest the need for future
empirical research in the following areas: (1)
the effectiveness of the SSI in identifying central auditory pathology when using different
competition materials, (2) inter- and intrasubject reliability with listeners with hearing impairment, (3) practice/learning or fatigue effects in
listeners with hearing impairment, and (4)
test-retest reliability using adaptive versus percent-correct procedures .
Acknowledgments. We thank VivekAjmani and Wayne
King for their statistical contributions to this project.
Portions of this paper were presented at the 7th
Annual Meeting of the American Academy of Audiology,
Dallas, TX, April 1995 .
REFERENCES
Beattie RC, Clark N. (1982) . Practice effects of a fourtalker babble on the synthetic sentence identification
test . Ear Hear 3:202-206 .
Cacace AT, Goldstein JC, Parries SM, Satya-Murti S,
Wolpaw, JR . (1984) . Psychoacoustic and electrophysiologic effects of partial eighth nerve damage . Am J
Otolaryngol 5 :43-48 .
SSI Reliability/Pugh et al
Cooper JC, Gates GA. (1991) . Hearing in the elderlythe Framingham cohort, 1983-1985: Part II . Prevalence
of central auditory processing disorders. Ear Hear
12 :304-311 .
Cooper JC, Gates GA. (1992) . Central auditory processing in the elderly: the effects of pure tone average and
maximum word recognition . Ear Hear 13 :278-280 .
Levitt H. (1971) . Transformed up-down methods in psychoacoustics . JAcoust Soc Am 49 :467-477 .
Levitt H, Rabiner LR . (1967) . Use of sequential strategy
in intelligibility testing. JAcoust Soc Am 42 :609-612 .
Lew H, Jerger J. (1991) . Effect of linguistic interference
on sentence identification . Ear Hear 12:365-367 .
Crandell C. (1991) . Individual differences in speech-recognition ability: implications for hearing aid selection. Ear
Hear 12:100-108 .
Martin FN, Mussell SA . (1979) . The influence of pauses
in the competing signal on synthetic sentence identification scores . J Speech Hear Disord 44:282-292 .
Crandell C, Boney S. (1998) . Speech recognition in the
clinical setting: an alternative approach . Paper submitted to Am J Audiol .
Marvel JB, Jerger JF, Lew HL . (1992) . Asymmetries in
topographic brain maps of auditory evoked potentials in
the elderly. JAm Acad Audiol 3:361-368 .
Del-Dot J, Hickson LM, O'Connell B . (1992) . Speech perception in noise with BICROS hearing aids . Scand Audiol
21 :261-264 .
Dubno JR, Dirks DD . (1983) . Suggestions for optimizing
reliability with the synthetic sentence identification test .
J Speech Hear Disord 48 :98-103.
Fire KM, Lesner SA, Newman C. (1991) . Hearing handicap as a function of central auditory abilities in the
elderly. Am J Otolaryngol 12 :105-108 .
Hayes D, Jerger J. (1979a). Low-frequency hearing loss
in presbycusis. Arch Otolaryngol 105:9-12.
Hayes D, Jerger J. (1979b) . Aging and the use of hearing aids . Scand Audiol 8:33-40 .
Jerger J, Hayes D. (1976) . Hearing aid evaluation : clinical experience with a new philosophy. Arch Otolaryngol
102:214-225 .
Jerger J, Speaks C, Trammell J. (1968) . Anew approach
to speech audiometry. J Speech Hear Disord 33:318-328 .
Jerger S, Jerger J. (1975) . Extra- and intra-axial brain
stem auditory disorders . Audiology 14 :93-117 .
Katz J, Stecker N, Henderson D, eds. (1992) . Central
Auditory Processing: A Transdisciplinary View . St. Louis:
Mosby Year Book .
Kricos PB, Lesner SA, Sandridge SA, Yanke RB . (1987) .
Perceived benefit of amplification as a function of central auditory status in the elderly. Ear Hear 8:337-342 .
Orchik DJ, Roddy N. (1980) . The SSI and NU-6 in clinical hearing evaluation . J Speech Hear Disord 45 :401-407 .
Plomp R. (1986) . A signal-to-noise ratio model for the
speech-reception threshold of the hearing impaired . J
Speech Hear Res 29 :146-154 .
Plomp R, Mimpen AM . (1979) . Improving the reliability
of testing the speech reception threshold for sentences .
Audiology 18 :43-52 .
Rodriguez GP, DiSarno NJ, Hardiman CJ. (1990) . Central
auditory processing in normal-hearing elderly adults .
Audiology 29 :85-92.
Speaks C. (1967) . Intelligibility of filtered synthetic sentences, J Speech Hear Res 10 :289-298 .
Speaks C, Jerger J. (1965) . Method for measurement of
speech identification . J Speech Hear Res 8:185-194 .
Speaks C, Jerger J, Jerger S. (1966) . Performance-intensity characteristics of synthetic sentences . J Speech Hear
Res 9:305-312 .
Thorndike EL, Large I. (1944) . The Teachers'Word Book
of 30,000 Words. New York: Columbia University Press.
Toscher MM, Rupp RR . (1978) . A study of the central
auditory processes in stutterers using the synthetic sentence identification (SSI) test battery. JSpeech Hear Res
21 :779-792 .
Willeford JA, Burleigh JM . (1994) . Sentence procedures
in central testing. In : Katz J, ed . Handbook of Clinical
Audiology. 4th Ed . Baltimore: Williams and Wilkins,
256-268.