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

for listeners to correctly detect the occurrence of the BIC increased rapidly.
This elevation in the duration threshold was faster under the
headphone-stimulation condition than the loudspeaker-stimulation condition.
Also, the listeners reaction time in response to the BIC but not that to
a comparable silent gap elongated quickly with the increase in the intersound
delay from 1 to 8 ms. Thus the auditory memory of fine structures
fades rapidly after the sound waves are received. Work supported by
MSTC and NSERCC.
5aPP19. Evidence for a cancellation mechanism in perceptual
segregation by differences in fundamental frequency. John F. Culling,
Gareth M. Linsmith, and Tracy L. Caller School of Psych., Cardiff Univ.,
Tower Bldg., Park Pl. Cardiff, CF10 3AT, UK
Identification of target speech material is better when it differs in fundamental
frequency (F0) from interfering speech material. Two experiments
tested the idea that this effect is mediated by a cancellation process
that perceptually removes sound on one F0. Expt. 1 used monotonized
target speech at 112.5 Hz F0 against two monotonized interferers. The
F0s of the interferers were either both 112.5 Hz, both 126 Hz, or 100 and
126 Hz. Speech reception thresholds SRTs were about 3.5 dB lower
when the two interferers shared a 126 Hz F0 than in the other two conditions,
which differed by only 0.3 dB. These results are consistent with a
cancellation mechanism that is able to remove sounds at only a single F0.
Expt. 2 replicated and extended Expt. 1, testing whether the results were
affected by the allocation of the target and interferers to particular F0s.
When all sentences shared a common F0, SRTs were now 1–1.5 dB
higher than when they were all different. However, all 4 SRTs for interferers
sharing the same F0 differing from that of the target by 2 or 4
semitones were lower than all three of the SRTs for interferers with independent
F0s.
5aPP20. Effects of high-frequency amplification and training on
impaired-listeners’ ability to discriminate redundant cues. Blas
Espinoza-Varas, Shelagh Bowman-Edmundson, and Hyunsook Jang
Commun. Sci. and Disord., Univ. Oklahoma Health Sci. Ctr., Oklahoma
City, OK 73190
This paper examines effects of high-frequency amplification and training
on the ability to discriminate redundant duration increments added
simultaneously to the low (L) and high (H) frequency component of
two-component complexes. The frequency of L 500 or 1000 Hz, 80 ms
and H 2000 or 3127 Hz, 60 ms was chosen so as to stimulate simultaneously
normal- and impaired-sensitivity regions of high-frequency sensorineural
patients. The 3I/2AFC task displayed a standard followed by
two comparisons. Duration increments in L, H, or both (tL, tH,ortLH),
occurred randomly in comparison 1 or 2, and listeners had to decide which
had an increment. The training stages were: 1 no H amplification, with
L35, H5 dB SL and tL, tH, and tLH; 2 H amplification, same as
before but with H35 dB SL; 3 H amplification and tH discrimination
training, same as stage 2, but with tH only and H in isolation or together
with L; and 4 retest of stage 2, post tH discrimination training. Only in
stage 4 did redundancy yield a significant improvement in overall discrimination
accuracy; amplification alone yielded little improvement.
5aPP21. Wideband reflectance in normal and otosclerotic ears. Navid
Shahnaz and Karin Bork Univ. of British Columbia, School of Audiol. &
Speech Sci., 5804 Fairview Ave., Vancouver, BC, Canada V6T 1Z3,
nshahnaz@audiospeech.ubc.ca
For years immittance has been used in order to help diagnose middle
ear pathologies. Specifically, multi-frequency tympanometry MFT is
able to relate information regarding the mechano-acoustical characteristics
of the middle ear system. In the past two decades a new method of middle
ear measurement, wideband reflectance WBR, has been introduced.
WBR is the ratio of energy reflected from the surfaces of the ear canal and
middle ear on its way to the cochlea in relation to the energy that reaches
the surface, or incident energy. This ratio is known as energy reflectance.
This paper adds to the limited normative data available, as well as explores
whether these normative data have a clinical utility in the diagnosis
of otosclerosis. Descriptive statistics were gathered from 62 115 ears
Caucasian normal hearing adults as well as in seven patients seven ears
with otosclerosis. All of the otosclerotic patients in this study deviated
from the normative values on at least one of the four WBR parameters of
power absorption, admittance, susceptance, or conductance even when
their MFT results were within normal limits. Although only seven patients
were tested, these results provided evidence in favor of the utility of WBR
for diagnosis of otosclerosis.
5aPP22. Sensitivity to combined frequency and amplitude speech cues
by cochlear implant users. Eric W. Healy, Cheryl F. Rogers, and Allen
A. Montgomery Dept. of Commun. Sci. and Disord., Arnold School of
Public Health, Univ. of South Carolina, Columbia, SC 29208,
ewh@sc.edu
Although a considerable amount of work has been directed toward
examining the sensitivity of the cochlear implant CI user to various
acoustic cues, less has examined the ability to combine cues. The sensitivity
to concurrent cues was examined using an adaptive 3I-2AFC paradigm.
Stimuli were synthesized three-syllable words having middle syllables
that possessed an increase in fundamental frequency, amplitude or
both. Sensitivity to increments in the individual cues was first measured
for five subjects with a CI and five age-matched controls. These DLs were
then used to equate sensitivity to the two cues and create stimuli having
concurrent increments. It was found that the presence of the two cues
reduced the mean DL to half that of either cue alone, for both groups of
subjects. Thus, this combination of cues is similar across groups and simply
additive. Individual differences in the ability of CI users to combine
cues were more strongly predictive of performance on speech recognition
tests than was sensitivity to either cue alone. These results have implications
for the perception of the multiplicity of speech cues. Work supported
by NIDCD.
5aPP23. Recognition of vowels that have been spectrally warped
according to the frequency map for the spiral ganglion. Peter S.
Popolo and Christoper W. Turner Dept. of Speech Pathol. and Audiol.,
119 WJSHC, The Univ. of Iowa, Iowa City, IA 52242,
peter-popolo@uiowa.edu
The purpose of this study was to explore the effect of a specific spectral
warping on vowel recognition in cochlear implant users. The warping
was designed to simulate the misalignment of frequency-to-place stimulation
which occurs if the spiral ganglion cells are electrically stimulated
instead of the eighth-nerve dendrites in the organ of Corti. Simulated
CIS-processed vowel stimuli were generated in which the analysis and
carrier band center frequencies were shifted according to the projection of
the spiral ganglion cells onto the organ of Corti, derived from published
data A. Kawano, H. L. Seldon, and G. C. Clark, Ann. Otol. Rhinol.
Laryngol. 105, 701–709 1996. Similar spectral warping was applied to
unprocessed vowel stimuli. Listening experiments were conducted in
which normal hearing subjects were presented with four types of stimuli:
unprocessed-unwarped, processed-unwarped, unprocessed-warped, and
processed-warped. For each condition, performance was allowed to stabilize
over repeated trials with feedback, to allow for learning. Vowel recognition
scores averaged across listeners were drastically reduced for the
warped stimuli, regardless of whether the stimuli were CIS-processed or
not. The combination of spectral warping and reduced spectral resolution
resulted in the poorest intelligibility scores. These results may have implications
for the design of frequency-to-place maps in cochlear implants.
2600 J. Acoust. Soc. Am., Vol. 117, No. 4, Pt. 2, April 2005 149th Meeting: Acoustical Society of America 2600