Stimulus Type and Language Ability Impact SRT in Normal-hearing Children
Ishara Ramkissoon, Ph.D., CCC-A, & Julie M. Estis, Ph.D., CCC-SLP
University of South Alabama, Mobile, AL
INTRODUCTION
METHODS
Pediatric Speech Audiometry
Speech recognition threshold (SRT) tests measure hearing threshold for speech
signals based on a 50% recognition level. SRT is an integral part of audiological
evaluation in children. It is often the only complete test if the child is difficult-to-test
or otherwise uncooperative. In clinical practice, pediatric SRT protocols are often
modified (reduced set size, different response mode) to accommodate limited
attention span or unfamiliarity with test words. However, these practices are known
to result in inaccuracies like underestimating the hearing threshold for speech
(Meyer & Bilger, 1997). In this case, SRT does not match the pure-tone average
(PTA) within 5-6 dB as expected.
Stimuli
• Digits (1-9, excluding 7) & CID-W1 words recorded, 44100 Hz sampling rate,
CSL Model 4500, speaker was a female audiologist (native English speaker)
• Stimulus files edited with Adobe Audition. Digits were paired (e.g., 2-4, 9-3)
• Recorded stimuli edited to increase homogeneity of audibility:
• Mean duration = 2.08 for digit pairs, 2.01 for CID-W1 words
• Mean amplitude = 22.49 for digit pairs, 22.58 for CID-W1 words.
• Stimuli randomly presented, Windows Media Player (Dell PC), routed via GSI61 audiometer to binaural ER-3A insert earphones, 1000 Hz calibration tone.
SRT Test Materials
Bisyllabic words with equal stress on each syllable (spondees) are preferred for
speech threshold tests because they have the highest homogeneity of audibility
(Egan, 1948). The second important criterion is familiarity with the speech stimuli,
which is essential for SRT testing. Test material selection for SRT is crucial for
ensuring valid clinical practice by assessing auditory skills, not language or
education.
SRT testing in Children
‰ Word learning deficits and late acquisition of the first 50 words are hallmark
characteristics of children with specific language impairment (SLI) (Leonard, 1998).
SLI children may not be familiar with common words used in standard SRT testing.
Reduced word familiarity for SLI children may inflate speech thresholds, indicating
poorer hearing. Therefore, it would be useful to have an alternate SRT test for
children, especially those with language impairment.
‰ Children who are unfamiliar with English words may also have difficulty with some
test items. Some audiologists might use language specific tests, where SRT stimuli
are presented in the child’s native language. Success of this practice occurs if the
audiologist speaks the test language.
‰ Adults who are new learners of English from differing linguistic backgrounds
perform well on digit SRT (DRT) tests (Ramkissoon et al, 2002). DRT has not been
evaluated in children but might be appropriate for children with language
i
impairment.
i
t
‰ Numbers 1-10 are learned early and are highly intelligible (Miller, et al., 1951),
making them a suitable stimulus for speech threshold tests. Numbers are typically
well-known to children, even those with language impairment (LI).
Purpose of the Present Investigation
The purpose of the current study is to evaluate an alternate SRT test in children.
Specifically, the relationship between the Digit-SRT and the CID WI-SRT stimuli will
be investigated in two groups of normal-hearing participants: children with language
impairment (LI) and age-matched, typically developing children (TD).
RESEARCH QUESTIONS
1. Do digit stimuli adequately measure hearing threshold for speech in TD
children?
2. Do digit stimuli adequately measure hearing threshold for speech in LI children?
3. Do DRT and WRT measure the hearing threshold for speech equivalently for TD
and LI children, when compared to pure tone average (PTA)?
p
Tasks
Experimental
• One experimental session, normal hearing + middle ear status confirmed
• SRT study measured hearing threshold for speech, IAC booth, using two tests:
• WRT test - 27 spondaic stimuli (e.g., “airplane, baseball, cowboy”)
• DRT test - 56 spondaic stimuli (e.g., one-nine, three-five).
• Familiarization with all stimuli before measurement began.
• Threshold seeking procedure: Experiment 1
• Pure tone testing: audiologist-preferred, clinical procedure (ASHA, 1994),
• 5-dB increment size, one PTA per ear was measured (PTAc)
• DRT and WRT test began at 40 dB, two stimuli presented, decreased 5dB each time both words correct (100%) until both words missed (0%).
• level above this was considered threshold if 50% was achieved
• bracketing method: 2-dB and/or 1-dB increment to reach 50% level
• one DRT and one WRT per ear were determined (DRTc, WRTc)
•Threshold seeking procedure: Experiment 2
• Pure tone testing, routine clinical procedure (5-dB), then 2-dB step size
• Two PTAs per ear were determined (PTA2, PTA5)
• DRT and WRT tests: recommended procedure for SRT test (ASHA ,1988)
• determination of starting level, and use of a correction factor
•Two DRT and two WRT determined per ear (e.g., DRT5, DRT2)
• Counter-balanced presentation order of familiarization lists and step sizes
Participants
• Children aged 5;0 to 8;11 years.
• Participants met the following inclusion criteria:
• passed a pure tone audiometric screening,
• normal cognitive abilities (scored 85 or > on Leiter International Performance Scale)
• no report of frank neurological or social-emotional impairments
• native English speakers.
• case history questionnaires - speech, language, and medical history
• omnibus, standardized language assessment (PLS-4/ CELF: Preschool 2/ CELF- 4).
• TD: language skills within one standard deviation (SD) of the mean
• LI: Total Language Score at least 1
1.25
25 SD below mean
Data Analysis
• Analysis I: N=25 children completed experiment 1
• Analysis II: N=22 children completed experiment 2
• Analysis III: N=12 children completed experiments 1 & 2
LI=9, TD=16
LI=4, TD=18
LI=2, TD=10
•NOTE: Data collection is ongoing in Experiment 2. Preliminary analyses are reported here.
Analysis I
Mean Thresholds (dB) for Each Group
Across Test Conditions
RESULTS
Analysis I
• A mixed model (Group, Tests) ANOVA with repeated measures on Tests (PTAc,
DRTc WRTc) revealed no significant difference between tests or groups (TD
DRTc,
(TD, LI)
LI).
• Due to differences in threshold seeking procedure in experiment 1, ANOVA run with
two tests (DSRT, W1SRT) revealed a significant difference (p=.022) due to mean
DRTc being higher (8.6 dB) than mean WRTc (7.4 dB) across 25 participants.
• Pearson correlation analyses revealed:
•All three tests highly correlated across 25 participants
• PTAc x DRTc = .71, PTAc x WRTc = .65, and DRTc x WRTc = .77.
•Significant difference (p=.000) between PTAc x DRTc (r=.81) and PTAc x WRTc
(r=.74) in TD children, however, no significant differences in LI children.
Analysis II (preliminary)
• A mixed model (Group, Tests) ANOVA , repeated measures on Tests (PTA2, DRT2,
WRT2, PTA5, DRT5, WRT5) revealed:
• Significant (p=.014) Group by Test interaction
• Significant main effects of Tests (p=.007) and Group (p=.003)
• Pairwise comparisons revealed significant differences between following Tests:
• PTA2-DRT2, PTA2-WRT2, PTA2-PTA5, and WRT2-WRT5.
•Group by Test interaction:
• No significant differences among Tests for the LI children (N=4)
• Significant (p=.004) difference among Tests in TD children (N=18)
•Pearson correlation analyses revealed :
• TD children: WRT x PTA (r=.66) significantly higher correlation than DRT x PTA
(r=.5 to .57), for both 5dB and 2dB tests.
• LI children: no significant difference in how WRT or DRT correlated with PTA.
Analysis III (preliminary)
• Two-factor (group, tests) ANOVA, repeated measures on Tests: no significant
differences for LI or TD children who completed experiment 1 and experiment 2.
Analysis II
Mean Thresholds (dB) for Each Group
Across Test Conditions
DISCUSSION
• Overall mean thresholds across Tests (6) are much higher (poorer) in LI than TD
children. Also, standard errors are lower and the range is narrower for TD than LI
children.
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threshold measurements.
• In LI children, WRT2 mean threshold is much higher than any other test.
• For the 2-dB Tests, LI children had lower (better) mean thresholds for DRT (11.79 dB)
than WRT (16.13 dB), whereas TD children had similar mean thresholds for DRT (9.36
dB) and WRT (8.36 dB). Clinically, this might be important as the LI children perform
better with digits (better match to PTA) than CID-W1 words.
• For the 5-dB Tests, TD children had lower (better) mean thresholds for WRT (7.08
Table
dB) than DRT (9.28 dB), whereas LI children
had1:similar mean thresholds for DRT
(11.75 dB) and WRT (11.88 dB). The decibel difference between digits and words in
TD children likely has minimal clinical/practical significance
significance. Of note
note, the standard error
is smaller and the range is narrower for the digit stimuli than the CID-W1 stimuli in
determining hearing threshold for speech in TD children.
• Data collection is ongoing for Experiment 2. Analysis will be completed for TD and LI children.
SELECTED REFERENCES
American Speech Language Hearing Association (ASHA) (1994). Omnibus Survey. Rockville, MD: ASHA.
ASHA (1988)
(1988). Guidelines for Determining the Threshold Level for Speech
Speech. ASHA,
ASHA 3: 85-88
85-88. Available:
www.asha.org/policy
Egan, J.P. (1948). Articulation testing methods. The Laryngoscope, 58, 3-31.
Leonard, L. B. (1998). Children with specific language impairment. Cambridge: MIT.
Meyer, T.A. & Bilger, R.C. (1997). Effect of set size and method on speech reception thresholds in noise. Ear and
Hearing, 18, 202-209.
Miller, G.A., Heise, G.A., & Lichten, W. (1951). The intelligibility of speech as a function of the context of the test
materials. Journal of Experimental Psychology, 41, 329-340.
Ramkissoon, I., Proctor, A., Lansing, C., & Bilger, R. (2002). Digit Speech Recognition Thresholds (SRT) for NonNative Speakers of English. American Journal of Audiology, 11, 1-6.
CONTACT: [email protected]