FRIDAY MORNING, 20 MAY 2005 REGENCY E, 8:30 A.M. TO 12:00 ...

nificant impact on the intelligibility of speech compared to a normal F0
contour: the SRT for the flattened F0 contour being only 0.7 dB higher.
The SRT for the inverted contour, however, was 1.6 dB higher than for the
normal F0 contour. When the sentences were played against a singletalker
interferer, the overall effect was greater, with a 2.1 dB difference
between the normal and flattened conditions, and 3.3 dB between the
normal and inverted F0 contours. There was found to be no effect of
altering the F0 contour of the interferer, indicating that any abnormality of
the F0 contour serves to mask the intelligibility of the target speech, but
does not alter the effect of the interfering speech. Future research will
investigate the impact on speech intelligibility of similar manipulations of
a low-pass-filtered F0 contour.
the other varied from da-to-ja. Several dependent measures were derived
based on d’from signal detection theory. These measures were used
to assess category boundaries and to indirectly assess sensitivity to phonetic
changes in labeling category tokens along each continuum. The SLI
group showed less consistent identification performance along the ba-
wa series relative to the TD group, as well as reduced sensitivity to
phonetic changes along the continuum. On the da-ja continuum, the
SLI group revealed less consistent identification performance on the short
FTD end, but similar identification levels to the TD group at the long FTD
end. The overall results support the view that children with SLI reveal a
deficiency in the processing of speech sounds at the level of segmental
identity.
5aSC20. Perceptual strategies for identifying vowels produced by
speakers with dysarthria. Kate Bunton Dept. of Speech, Lang., and
Hearing Sci., Univ. of Arizona, P.O. Box 210071, Tucson, AZ 85721
It has been previously reported that changes to the fundamental frequency
contour of vowels influences their identification e.g., H. Traunmuller,
J. Acoust. Soc. Am. 69, 1465–1475 1981. Similar changes in
vowel identification have been demonstrated for some listeners when the
F0 contour of a dysarthric speaker has been modified e.g., flattened or
enhanced Bunton 2004. These listeners appear to rely on F0F1
space for identification of vowel height; this strategy is consistent with a
perceptual model of vowel recognition described by A. Syrdal and H.
Gopal J. Acoust. Soc. Am. 79, 1086–1100 1986. Other listeners, however,
appear to utilize different acoustic cues to identify a given vowel.
This study focused on defining those perceptual strategies. Multidimensional
plots of acoustic cues likely to influence vowel perception are
used to illustrate perceptual strategies that may have been used by these
listeners for identification of vowels in the speech of individuals with
dysarthria associated with Parkinson disease. Work supported by NIH
R03 DC005902.
5aSC21. Perception of coarticulation in gated words by dyslexic and
non-dyslexic children. Patricia Keating UCLA, Los Angeles, CA
90095-1543, Frank Manis, Jennifer Bruno, and Jonathan Nakamoto
USC, Los Angeles, CA 90089-1061
In an auditory word gating task, listeners are presented with portions
of words, and try to identify these acoustic fragments as lexical items. It
has been shown that children need more acoustic information than adults
to succeed, and that dyslexic children can require more information than
other children. It is also known that adults can use early acoustic cues to
identify features of upcoming segments. For example, in English anticipatory
vowel nasalization implies that a nasal consonant will follow, and
similarly anticipatory lateralization. Our study asked whether dyslexic
children are impaired in their perception or use of such anticipatory coarticulatory
information. Successive gates from test words that ended in a
nasal 8 words or /l/ 4 words, or control words with final oral stops,
were blocked by length and presented to 26 dyslexic and 26 non-dyslexic
children. Responses were audiorecorded and later transcribed; responses
were scored re both the full word and the nasality/laterality of the final
consonant. Dyslexics as a group required more gates to identify nasality,
but not whole words. Language-impaired dyslexics required more gates to
identify whole words as well as nasality. Performance on the gating task
significantly predicted reading ability when age and IQ were controlled.
5aSC22. Phonetic labeling along a formant transition duration
continuum in children with specific language impairment. Harvey M.
Sussman, Elizabeth Burlingame, Ronald B. Gillam Dept. of Commun.
Sci. & Disord., Univ. of Texas, Austin, TX 78712, and Jessica F. Hay
Univ. of Texas, Austin, TX 78712
Fifteen children diagnosed with specific language impairment SLI
and fifteen typically developing TD children were tested for identification
performance on two synthetic speech continuua varying in formant
transition durations FTDs. One continuum varied from ba-to-wa and
5aSC23. Classification of dysarthric and non-impaired speech based
on prosodic features. Greg Kochanski Oxford Univ., 41 Wellington
Square, Oxford OX1 2JF, UK, gpk@kochanski.org and Rupal Patel
Northeastern Univ., Boston, MA 02115
Prosodic differences between dysarthric and healthy speakers were
studied. Six acoustic properties that are plausibly more influenced by suprasegmental
aspects of speech e.g., emphasis than the segmental details
of the words were measured. The time course of these properties were
analyzed over each utterance by fitting Legendre Polynomials. The resultant
Legendre coefficients were then fed to linear- and quadraticdiscriminant
classifiers. All of the six properties were individually capable
of distinguishing dysarthric speech from healthy speech. Based on one
acoustic property measured over a single short sentence, we could correctly
classify a speaker as healthy or dysarthric 55–75% of the time,
depending on the acoustic property used. More complex classifiers that
used all the acoustic properties correctly classified the speaker 97% of the
time based on nine utterances. The strongest difference between normal
and dysarthric speech was in loudness. Dysarthric speakers did not reliably
produce the loudness patterns associated with stressed syllables. They
also had a wider range in amplitude, greater voicing variability, smaller
excursions of fundamental frequency, and less final lengthening compared
to healthy speakers. The classification we demonstrated may be extended
to a become a graduated measurement of severity, thereby contributing to
diagnostics and intervention in dysarthria.
5aSC24. Effects of hearing impairment on the perception and neural
representation of time-varying spectral cues. Ashley W. Harkrider,
Patrick N. Plyler, and Mark S. Hedrick Dept. of Audiol. and Speech
Pathol., Univ. of Tennessee, 457 South Stadium Hall, Knoxville, TN
37996
Differences in phonetic boundaries versus normal controls suggest that
listeners with hearing impairment HI have difficulty categorizing stop
consonant place of articulation based solely on the dynamic spectral information
present in the second formant transition (F2), even when the
stimuli are amplified. This may be due to a degraded ability of the central
auditory nervous system to process time-varying spectral cues despite ensuring
overall audibility. However, increasing the overall level of the
stimuli may not result in improved audibility of F2. To determine if spectral
shaping of F2 improves performance of listeners with HI, psychometric
functions and N1-P2 cortical responses were compared in 10 older
listeners with normal hearing versus 10 older listeners with HI. Stimuli
were synthetic consonant-vowels along a /ba/-/da/-/ga/ place-ofarticulation
continuum in an unshaped and shaped condition. Generally,
behavioral and N1-P2 results indicate that, with shaping, categorization
of /d/ and /g/ improves. These findings suggest that enhanced audibility of
F2 through spectral shaping does improve perception of stop consonant
stimuli. However, categorical boundaries for the individuals with HI are
shifted lower in frequency with shaping for all phonemes versus normal
controls, indicating that enhancing audibility improves but does not completely
normalize categorization performance.
5a FRI. AM
2607 J. Acoust. Soc. Am., Vol. 117, No. 4, Pt. 2, April 2005 149th Meeting: Acoustical Society of America 2607