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Biomedical subjects

G Kidd

Publications and source records attributed to G Kidd.

34 records · Page 2Linked to original sources
PubMed1986

Auditory profile analysis of irregular sound spectra.

The discrimination of changes in the shapes of sound spectra is reported. The change was always an intensity increment to the 948-Hz component of a multitone complex. First, the ability of naive listeners to learn to discriminate a change in a "regular" background or reference spectrum (equal-level tones equally spaced in logarithmic frequency) was measured as a function of the number of trials. On the average, threshold improved about 10 dB over 3000 trials, with about 50% of the decrease in threshold occurring during the first 750 trials. In a subsequent series of experiments, the overall pattern of spectral shape of the background was varied randomly. Two kinds of perturbations in spectral shape were employed: Randomly choosing the frequencies of the reference spectra and randomly choosing the amplitudes of the components of the reference spectra. The experimental manipulations involved fixing the random spectra across a block of trials, varying the reference spectra from interval to interval of each trial, and providing extensive practice in discriminating specific randomly perturbed reference spectra. The results of the spectrum-learning and random perturbation experiments provide insight into the roles of critical band filtering, sensory variability, and short-term and long-term memory representations in auditory profile analysis. Further, the appropriateness of the generalization of a simple energy detection model is discussed.

Acoustic Stimulation↗
PubMed1984

Profile analysis and level variation.

This study examines the effects of random level variation, a method used in studies of profile analysis [3-6,14,15]. Presentation levels for a complex of sinusoids are varied randomly on each interval of a two-interval, forced-choice detection task in which subjects are required to detect an increment on one of the sinusoidal components of the complex. Three experiments are reported. The first experiment examines the effect of the range of level variation. The second is concerned with the effects of the median level about which the presentation levels vary. The third experiment is designed to provide a within-trial analysis of the effect of the differences in presentation levels. As the range of level variation is increased, ability to detect the increment decreases. The results indicate that detection performance is best at moderate intensity levels and decreases at lower and higher levels. Finally, the difference in levels within a single trial has little if any effect.

Acoustic Stimulation↗
PubMed1984

Temporal integration of forward masking in listeners having sensorineural hearing loss.

Findings are described from three experiments that were designed to contrast estimates of auditory time and frequency analysis in highly practiced, young adult subjects having sensorineural hearing loss of cochlear origin with subjects having normal hearing. In one experiment, pure-tone detection threshold was measured for two durations of tones. For the hearing-impaired subjects, smaller differences were found between thresholds for the two durations of tones than were found for the normally hearing subjects at test frequencies where the sensitivity loss was greatest. In a subsequent forward masking experiment, masked thresholds were obtained at 3 kHz as a function of masker level at several masker durations. The results indicated that, for the range of values tested, masked probe thresholds changed less as a function of masker duration for the hearing-impaired subjects than for normally hearing subjects. However, forward masking grew as a function of masker level more steeply for the hearing-impaired listeners than for the normally hearing listeners. We believe that this result indicates abnormal temporal processing of sequential sounds. In a third experiment, psychophysical tuning curves were measured in a forward masking procedure for two maskers that differed in duration by approximately an order of magnitude. Again, the hearing-impaired subjects demonstrated less change in forward masking as a function of masker duration than normally hearing subjects. Further, the sharpness of the tuning curves from the hearing-impaired listeners was markedly reduced as compared to normal. It is believed that the results reflect a disruption of the normal temporal and spectral representation of sounds in the hearing-impaired subjects.

Auditory Threshold↗
PubMed1984

Profile analysis: critical bands and duration.

The detection of an increment in the intensity of the central component of a multi-component complex was measured as a function of the frequency spacing of the components and the duration of the presentation. The overall intensity of the complex was randomly varied on each presentation of the stimulus. Curiously, the increment becomes easier to hear as the range and density of the surrounding complex is increased. This increase in range and density is also effective in improving the detectability of the increment when there is no random variation in intensity, i.e., a conventional Weber fraction experiment. This is unlike the results obtained in many other critical-band experiments where energy remote from the signal frequency has little or no effect. Measurement of the effects of signal duration showed that when presentations were shorter than about 100 msec a greater increment in intensity was required than for longer durations. These results with duration are similar to those obtained in other intensity-discrimination tasks.

Discrimination Learning↗
PubMed1984

Some effects of rhythmic context on melody recognition.

The effects of rhythmic context on the ability of listeners to recognize slightly altered versions of 10-tone melodies were examined in three experiments. Listeners judged the melodic equivalence of two auditory patterns when their rhythms were either the same or different. Rhythmic variations produced large effects on a bias measure, indicating that listeners judged melodies to be alike if their rhythms were identical. However, neither rhythm nor pattern rate affected discriminability measures in the first study, in which rhythm was treated as a within subjects variable. The other two studies examined rhythmic context as a between subjects variable. In these, significant effects of temporal uncertainty due to the number and type of rhythms involved in a block of trials, as well as their assignment to standard and comparison melodies on a given trial, were apparent on both discriminability and bias measures. Results were interpreted in terms of the effect of temporal context on the rhythmic targeting of attention.

Adult↗
PubMed1983

Successive versus simultaneous comparison in auditory intensity discrimination.

The ability to discriminate between two brief sounds having identical frequency components, but differing in the intensity of one or more of the components, is studied. The stimulus manipulations include randomizing the overall intensity of the sounds, varying the number and spacing of the components, and varying the interval of time between the sounds. The results from the experiment in which interstimulus interval is manipulated clearly support a profile analysis mechanism that computes two rough spectral analyses, stores a classification of these spectra in memory, and compares the two stores. This profile mechanism involves a simultaneous comparison of different components of the complex, some remote from the signal frequency, rather than a successive comparison of the difference in intensity at the signal frequency. The simultaneous comparison process is more sensitive when the profile is composed of many components spaced over a wide frequency range.

Discrimination, Psychological↗
PubMed1983

Further studies of auditory profile analysis.

The discrimination of a change in the intensity of a component or components of a multitone complex is reported as a function of a number of experimental variables. In one experiment, changes in the shape of the spectrum were explored to determine which kinds of changes are more easily detected. Although different signal spectra produced different thresholds, the change in a single component produced the lowest threshold on an energy basis. Various binaural conditions were tested to determine if the shape or profile of the stimulus could be supplied by the ear opposite the one in which the signal was presented. Conditions where spectral contrasts were available to both ears simultaneously (diotic conditions) were much more sensitive than conditions where the spectral contrasts occured for opposite ears (dichotic conditions). Finally, the level of the component at the signal frequency was varied relative to the other, equal amplitude, components to form a "pedestal" upon which the signal was added. Detection of the signal was roughly the same for pedestal levels within about +/- 12 dB of the background except for conditions where masking was apparent.

Auditory Threshold↗
PubMed1981

Patterns of residual masking.

"Residual masking' was measured in a tonal forward masking paradigm. In one experiment, psychophysical tuning curves and masking patterns were obtained at several frequencies and levels for a fixed masker-probe time delay. In a second experiment, tuning curves and masking patterns were measured as masker-probe time delay was varied. Our results indicate that tuning curves and masking patterns are sharpest at low levels, high frequencies and brief masker-probe time delays. In addition, we observed that masked probe threshold returned to the level of unmasked probe threshold at approximately the same post-masker time regardless of masker level or the probe-to-masker frequency relationship. These findings suggest that frequency, level and time delay all affect the degree of frequency selectivity observed with these measures.

Adult↗
PubMed1981

Evidence for rhythmic attention.

Three studies compared effects of different rhythmic contexts on order judgments of targets embedded in auditory patterns designed to manifest auditory stream segregation. Of interest was the effect of rhythmic structure upon the frequency-based captor effect, wherein tones in one stream "capture" those of similar frequencies from another. Three rhythmic structures were studied. Experiment 1 compared a rhythm conducive to pairwise-target stream formation with one conducive to a four-tone stream, and one based on an isochronous rhythm in a within-subjects design. Patterns embedding the target tone pair contained a preliminary string of captor tones at frequencies either close or far from frequencies of distracting tones that flanked the target pair. No effect of captor distance was found. Experiments 2 and 3 varied rhythm between subjects using 9- and 11-tone patterns, respectively. In general, the magnitude of the captor effect was found to vary with temporal predictability of flanking and/or target tones. The pairwise rhythm was most likely to improve order judgments by facilitating frequency-based capture. Results are discussed in terms of a rhythmic attentional hypothesis.

Attention↗
PubMed1981

Psychophysical scaling of distorted speech.

Magnitude estimation and magnitude production procedures were used by ten normal-bearing subjects to scale the perceived distortion corresponding to the systematically varied physical distortion of a speech signal. The combined function based on the results of the two procedures exhibited a slope of 0.83, indicating that perceived distortion grows more slowly than physical distortion.

Adult↗