Recent Abstracts
From the 151st meeting of the Acoutical Society of America (2006):
Response-related patterns
in discrimination of FM narrowband noise
Jinyu Qian and Virginia M. Richards
Department of Psychology, University of Pennsylvania
Noise stimuli were used to investigate weighting patterns for detecting
dynamic frequency changes. For one stimulus set, a tonal glide was
modulated by a narrow band of noise (gliding narrowband noise, GNBN,
condition). For the second set, the glide was preceded and followed
by steady-state tones before modulation (SS condition). The task
was to indicate whether the stimulus had a frequency glide or not.
Weighting patterns (as a function of time) were derived for each
subject based on a linear classification model. First, the deviation
of the instantaneous carrier for each stimulus was calculated and
then weighted by the squared envelope of the stimulus. This was
followed by the linear classifications of the squared-envelope-weighted-deviation-of-instantaneous-carrier
(SEWDOIC) according to the subject’s responses [A. Ahumada,
J. Vis., 2, 121-131 (2002)]. The weighting patterns were consistent
across subjects although individual differences in pattern details
were observed. The comparison between the patterns from the GNBN
and SS conditions indicates the use of dynamic information rather
than only comparing the beginning and ending frequencies, consistent
with Lyzenga et al. [J. Acoust. Soc. Am., 116, 491-501 (2004)].
Similar weighting patterns were also estimated when the center frequency
of the stimuli was random.
From the 29th midwinter meeting of the Association for Research
in Otolaryngology (2006):
Simultaneous Two-Channel
Signal Detection, revisited
Gerald Kidd Jr.1, Virginia M. Richards2, Christine R. Mason1, Frederick
J. Gallun1, and Rong Huang2
1Department of Speech, Language and Hearing Sciences and Hearing
Research Center, Boston University, Boston, MA
2Department of Psychology, University of Pennsylvania
This study examined the ability of listeners to monitor events occurring
simultaneously in two widely spaced frequency regions. The task
was to detect the presence of a low frequency (558 Hz) tone and
a high frequency (1791 Hz) tone presented in a 2- interval 4-alternative
forced-choice procedure. On every trial, each signal was presented
in either the first or second interval independently and the listener
was required to indicate the interval of presentation for each signal.
The level of each signal was varied separately according to an adaptive
tracking procedure to obtain threshold estimates. As a control,
thresholds for both signals were also obtained for single-signal
presentation. Comparison of thresholds in single- and dual-signal
presentation conditions provided an estimate of the costs of monitoring
and responding to events in two frequency channels. Signal thresholds
were obtained in quiet, in double-notch-filtered Gaussian noise,
and in random-frequency multitone maskers. Much larger costs (difference
between dual- and single-tone tasks) were found for the masked conditions,
especially for the multitone masker. These results suggest that
the costs of dividing attention along a particular stimulus dimension
depends on both the resources required to solve the task in each
signal channel and also the resources required to ignore competing
stimuli in nonsignal channels. [Work supported by AFOSR and NIH/NIDCD]
From the 149th meeting of the Acoutical Society of America (2005):
Effect of signal frequency
uncertainty for random multi-burst maskers
Rong Huang and Virginia M. Richards
Department of Psychology, University of Pennsylvania
The detectability of a sequence of equal-frequency tone pips masked
by random multi-burst complexes may depend on the perceptual segregation
of the signal stream from the random masker. If so, detection thresholds
may be independent of whether the signal frequency is known versus
uncertain. In this experiment observers detected a signal stream
of 8 sequential equal-frequency 30 ms tone pips embedded in a random
masker composed of 8 sequential bursts. A yes/no procedure was used,
and the independent variable p (probability a tone was played at
a particular time-by-frequency location) governed the number of
masker tones in each burst. The dependent variable was d. Threshold
values of p were obtained for signal streams at 5 different frequencies.
Sensitivity was superior for the mid-frequency signal, and decreased
as the signal frequencies approached the edge of the frequencies
the masker tones occupied (200--5000 Hz). When the frequency of
the signal stream was randomly varied from trial to trial, sensitivity
was poorer than for any of the fixed-frequency signals. Thus, the
detectability of a sequence of tone pips is reduced when the signal
frequency is uncertain compared to certain. Additionally, sensitivity
increased when the signal stream was delayed relative to the masker
bursts.
From the 149th meeting of the Acoutical Society of America (2005):
Comparing linear regression
models applied to psychophysical data
Zhongzhou Tang1, Andrew Shih2 and Virginia M. Richards1
Dept. of Psychology1, Dept. of Bioengineering2, University of Pennsylvania
Relative weights for a profile analysis task were obtained using
four regression/classification models; correlation coefficients,
linear regression, logistic regression and probit regression. The
aim of the study was to examine the impact of the choice of model
on the accuracy and the efficiency with which the relative weights
were determined. A yes/no task was used with observers indicating
whether or not there was an increment in level to the central component
of an 11-component standard. On each presentation the amplitudes
of the individual components of the complex were randomly perturbed
using draws from a normal distribution. When a large number of trials
(1250) were used to estimate the relative weights, the four methods
generated nearly identical weight estimates. When smaller numbers
of trials were used (112), the different methods generated patterns
of relative weights that were largely similar, and the patterns
deviated only modestly from the large-number solution. In terms
of efficiency, the error boundaries of the different methods were
nearly indistinguishable. All in all, the number of trials needed
to obtain statistically significant weights is sufficiently large
that there is no apparent advantage of using one method over the
others. [Work supported by NIH/NIDCD.]
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