Biomedical subjects

H S Colburn

Publications and source records attributed to H S Colburn.

At least 19 recordsLinked to original sources

PubMed1994

Reducing informational masking by sound segregation.

Informational masking was reduced using three stimulus presentation schemes that were intended to perceptually segregate the signal from the masker. The maskers were sets of sinusoids chosen randomly in frequency and intensity on each stimulus interval or, in some conditions, on every masker burst in a series of bursts within intervals. Masker components were excluded from the frequency region surrounding the 1000-Hz signal to minimize the energetic masking. Masked thresholds as great as 60-70 dB above quiet threshold were observed for some subjects in some conditions. It was shown that this informational masking could be reduced as much as 40 dB by: (1) presenting the masker to both ears and signal to one ear; (2) playing different masker samples sequentially in each interval of every trial; or (3) presenting the signal in alternate bursts of multiple, identical masker samples. For the binaural manipulation, informational masking was reduced because the masker and signal were perceived as originating from different interaural locations. In the latter two manipulations, a difference in the spectral or temporal pattern of the signal and masker provided the detection cue. These effects were interpreted as evidence of the importance of perceptual segregation of sounds in noisy listening environments where signal reception is not limited by energetic masking.

Acoustic Stimulation↗

PubMed1992

Frequency dependence of binaural performance in listeners with impaired binaural hearing.

Binaural performance was measured as a function of stimulus frequency for four impaired listeners, each with bilaterally symmetric audiograms. The subjects had various degrees and configurations of audiometric losses: two had high-frequency, sensorineural losses; one had a flat sensorineural loss; and one had multiple sclerosis with normal audiometric thresholds. Just noticeable differences (jnd's) in interaural time, interaural intensity, and interaural correlation as well as detection thresholds for NoSo and NoS pi conditions were obtained for narrow-band noise stimuli at octave frequencies from 250-4000 Hz. Performance of the impaired listeners was generally poorer than that of normal-hearing listeners, although it was comparable to normal in a few instances. The patterns of binaural performance showed no apparent relation to the audiometric patterns; even the two subjects with similar degree and configuration of hearing loss have very different binaural performance, both in the level and frequency dependence of their performance. The frequency dependence of performance on individual tests is irregular enough that one cannot confidently interpolate between octaves. In addition, it appears that no subset of the measurements is adequate to characterize the performance in the rest of the measurements with the exception that, within limits, interaural correlation discrimination and NoS pi detection performance are related.

Acoustic Stimulation↗

PubMed1992

Test of a model of auditory object formation using intensity and interaural time difference discrimination.

A model of auditory object formation and an experimental evaluation of the model are described. Specifically, predictions for intensity discrimination and interaural time difference discrimination for the central component of a three-component harmonic complex are evaluated empirically. The onset time of the central, target component is varied relative to the onset times of the remaining, interferer components in order to vary the degree of fusion (versus perceptual segregation) of the target and the interferers. The model, which is based on the idea of attenuation of the components in the nonattended auditory image (in the case of segregated images), predicts lower sensitivity to information at the target component for the fused versus segregated target, and equal sensitivities for completely segregated targets and targets presented in isolation. Results are presented for four subjects with component frequencies of 400, 600, and 800 Hz and with onset time differences of 0 or 250 ms. The target duration was always 100 ms and offset times were the same for all components. The subjective results were as expected, with synchronous onsets yielding one sound object, and asynchrony of the central component yielding two sound objects. Also, the empirical results on interference in the synchronous case were in qualitative agreement with the above predictions. However, significantly more interference was found than was predicted for both synchronous and asynchronous conditions. In fact, the amount of interference found contradicts the simple attenuation model of object formation.

Adult↗

PubMed1991

Detection of tones in reproducible narrow-band noise.

Hit and false-alarm rates were measured for detection of a 500-Hz tone target in each of ten reproducible samples of 1/3-oct bandwidth noise centered at 500 Hz for both NoS pi and NoSo conditions. The effects on hit rates of the starting phase of the target relative to individual noise samples were investigated with two target phase angles for three subjects. The major results are: (1) performance varies significantly over masker waveforms; (2) for NoS pi conditions, the effect of target-to-marker phase angle on hit rates is not significant for these narrow-band maskers; (3) for NoSo conditions, the target-to-masker phase angle has a large effect; (4) no significant correlation between NoSo performance and NoS pi performance is seen across masker waveforms. These results are generally consistent wuth previously reported results for wideband maskers [R.H. Gilkey, D.E. Robinson, and T.E. Hanna, "Effects of masker waveform and signal-to-masker phase relation on diotic and dichotic masking by reproducible noise," J. Acoust. Soc. Am. 78, 1207-1219 (1985)] with an important exception. Specifically, in the wideband experiment, significant correlation between NoSo and NoS pi performance across noise samples was found. In addition, in the wideband experiment, a small yet statistically significant effect of target-to-masker phase was observed in the NoS pi condition.

Adult↗

PubMed1991

Fringed correlation discrimination and binaural detection.

Results are reported from a series of binaural detection and interaural correlation discrimination experiments at 500 Hz. The experiments include fringed correlation discrimination in which the correlation change is restricted to a narrow (38 Hz) target band of frequencies and the reference correlation is maintained in a fringe band of frequencies. This experiment is designed to be analogous to a detection experiment with a narrow-band target; in both cases the correlation changes only inside the target band. A simplified theoretical framework is used to compare the results of the detection and correlation discrimination experiments. Results are consistent with the notion that binaural detection and interaural correlation discrimination are effected by a common mechanism when the reference correlation is unity (as in the NoS pi case). When the reference correlation is zero (as in the NuSo case), detection performance is significantly better than predicted from the measured ability to discriminate interaural correlation.

Attention↗

PubMed1990

Coincidence model of MSO responses.

A simple coincidence model of MSO responses is presented. The model is notable in that it contains no inhibition beyond the synchronization to the fine structure of the stimulus as seen in auditory nerve firing patterns. Output patterns for model cells are simulated and compared with patterns observed in available recordings from EE cells in the MSO. Patterns are compared in terms of discharge rate, vector strength, and period histograms. The patterns generated by the model are found to provide an adequate representation of the data, and it is concluded that a more complex model is not required at this tme to describe available data on MSO firing patterns.

Algorithms↗

PubMed1989

Binaural processing of noisy stimuli: internal/external noise ratios for diotic and dichotic stimuli.

A set of ten digitized statistically similar Gaussian maskers was used in one-internal tone-in-noise detection experiments under diotic (NoSo) and dichotic (NoS pi) interaural conditions. Stimulus/response matrices were generated for each masker in the presence or absence of a target 500-Hz tone. For both NoSo and NoS pi, nonparametric analyses show that response probabilities and sensitivities vary significantly across noise waveforms, indicating a considerable external noise component in subject response variability. A parametric model is developed that maps individual stimulus waveforms onto a decision axis, facilitating evaluation of internal/external noise variance ratios. For both NoSo and NoS pi, internal and external noise variance are of similar magnitude.

Acoustic Stimulation↗

PubMed1986

Interaural correlation discrimination: II. Relation to binaural unmasking.

Many theoretical models of binaural interaction assume that sensitivity to interaural correlation underlies binaural unmasking. This paper explores the extent to which sensitivity to changes in interaural correlation implied by results from binaural detection experiments are consistent with sensitivity to changes in interaural correlation implied by results from binaural detection experiments are consistent with sensitivity to changes in interaural correlation measured directly in correlation discrimination experiments. The vehicle for this exploration is a simplified model of the underlying processes assumed by many models of binaural unmasking for the detection of narrow-band signals in the presence of broadband noise. Consideration is given to psychometric function slopes, detection thresholds, bandwidth effects, duration effects, level effects, and interaural-parameter effects. Although many of the results obtained from our analysis are consistent with the notion that the cue in binaural detection tasks is a change in interaural correlation, some significant inconsistencies are noted.

Acoustic Stimulation↗

PubMed1986

Performance in several binaural-interaction experiments.

The relationship between interaural correlation discrimination and binaural detection was investigated using common experimental procedures and common subjects. Psychometric functions were obtained for four normal-hearing subjects at 500 and 4000 Hz using third-octave noise signals for the correlation discrimination experiment, and pure-tone signals and third-octave noise maskers for the detection experiment. Results from these two measurements, which were compared by expressing the signal-to-noise ratio as an equivalent change in interaural correlation, support the idea that interaural correlation discrimination and binaural detection are closely related. Since large intersubject differences in binaural performance were observed in these experiments, interaural-time, interaural-intensity, and monaural-intensity discrimination were measured in a second experiment. The results of the second experiment show large intersubject differences for the interaural tasks, but not for the monaural task.

Acoustic Stimulation↗

PubMed1985

Lateral-position-based models of interaural discrimination.

This letter investigates the hypothesis that lateral position is the only cue available for interaural discrimination experiments using 500-Hz stimuli. The discussion of this hypothesis is in the context of comparisons of the experimental data to predictions of the "position-variable" model of binaural interaction. The model predicts the mean and variance of the subjective lateral position of stimuli used in the discrimination experiments, assuming that discrimination performance is based on optimal processing of this subjective position. To the extent that the laterality predictions of the model are accurate, data that are inconsistent with its predictions would also be problematical for any model based on the subjective laterality of a single binaural image. The predictions (at least qualitatively) describe much of the observed experimental data, including a number of results that have not been addressed by any previous theory. Nevertheless, the observed performance is significantly better than the corresponding predictions for three types of experiments in which the utility of the position cue has been eliminated by experimental design. We believe that our results indicate that changes in lateral position are the primary cue in most interaural discrimination experiments, but that secondary attributes of the perceptual images can be useful when performance based on position alone would be poor.

Auditory Perception↗

PubMed1983

Internal and external noise in binaural detection.

We studied the 2IFC detectability of a 500 Hz tone masked by computer-generated maskers under the N0SII interaural condition, and under two masker conditions. In the first masker condition the maskers in the two intervals of a trial were independent of each other, and in the second masker condition the maskers were identical, although maskers varied from trial to trial. Thresholds were higher for the independent-noise condition than for the identical noise condition. These results have implications for the Theory of Binaural Interaction Based on Auditory Nerve Data (Colburn, H.S. (1977): J. Acoust. Soc. Am. 54, 1458-1470; Colburn, H.S. (1977): J. Acoust. Soc. Am. 61, 525-533).

Auditory Threshold↗

PubMed1982

Masked discrimination of interaural time delays with narrow-band signal.

Interaural time just-noticeable-difference (jnd) of a narrow-band noise masked by a wideband noise was measured for nine different interaural configurations of the masking noise at a fixed signal-to-noise ratio. The narrow-band noise was 1/3 octave wide centered about 500 Hz, and the wideband masker was bandpass filtered between 250 and 1500 Hz. Our results are in agreement with earlier results with tones [M. F. Cohen, J. Acoust. Soc. Am. Suppl. 1 64, S35 (1978); J. Acoust. Soc. Am. 70, 1289-1293 (1981); J. E. Slocum and R. M. Stern, J. Acoust. Soc. Am. Suppl. 1 68, S60 (1980)] and are the opposite of what may be expected from the results of binaural detection experiments: the jnd is largest for the interaurally phase reversed masker and smallest for the diotic masker. In addition, no consistent relation was observed between the size of the jnd and the perceptual location of the masker. Predicted jnds were calculated from a model based on the interaural phase difference of the stimuli in the two ears and were in rough agreement with the experimental results.

Auditory Perception↗

PubMed1982

Free-field tests of hearing-impaired listeners: early results.

Results are reported from a series of free-field tests of five hearing-impaired listeners. The tests provide relatively crude estimates of listeners' abilities in three types of experiments: free-field masked detection, source angle discrimination (both horizontal and vertical), and identification of source direction. Relations between abilities in the various tasks are noted.

Audiometry↗

PubMed1982

Binaural interaction and localization with various hearing impairments.

Binaural interaction and localization abilities of hearing-impaired listeners are summarized separately for each of several types of hearing and neurological disorders. The dependence of binaural abilities on the nature of the impairment is emphasized. Unfortunately, available data are not sufficient to characterize the specific aspects of the stimulus information available in each type of impairment.

Auditory Perception↗

PubMed1981

Interaural correlation discrimination: i. bandwidth and level dependence.

Measurements of interaural cross-correlation jnds from two reference correlations at several bandwidths were obtained for constant-total-power and constant-spectral-power Gaussian noise. At a reference correlation of 1, the results indicate that for bandwidths less than or equal to 115 Hz the jnd remains at a constant value of approximately 0.004, and monotonically increases (discrimination performance degrades) to approximately 0.04 as bandwidth increases above 115 Hz. At a reference correlation of 0, the jnd decreases (discrimination performance improves (from approximately 0.7 to 0.35 as the bandwidth increases from 3 to 115 Hz, and remains at a constant value of approximately 0.35 for bandwidths greater than 115 Hz. A decrease in the spectral level causes an increase in the jnds at a reference correlation of 1, and no change in the jnds at a reference correlation of 0. Of the three models tested, none is able to completely describe all of the empirical results.

Differential Threshold↗

PubMed1981

Binaural interaction of impaired listeners. A review of past research.

This paper reviews past studies of binaural interaction in impaired listeners. The topics covered include localization and lateralization; equal loudness, centering and lateralization adaptation; detection of signals in noise; and discrimination of interaural time delay and interaural amplitude ratio. Comments concerning experimental design and procedures, as well as interpretation of results, are often included with descriptions of the studies.

Auditory Perception↗

PubMed1979

Discrimination of symmetric time-intensity traded binaural stimuli.

Experiments were conducted to determine the extent to which listeners can discriminate between different combinations of interaural time and intensity for binaural stimulus configurations which eliminate loudness, lateralization, and image-diffuseness cues. A two-interval forced choice paradigm was used, and the task of the subject was to determine the order of two stimuli, each of which was a slowly gated 500-Hz tone with a combination of interaural time and intensity differences that resulted in a centered primary spatial image. The two stimuli to be discriminated were symmetric in that they differed only in the polarity of their interaural differences. Also, in order to reduce artifacts introduced by variations in the coupling of the earphones to the head, acoustic monitoring and compensation was performed both before and after each experimental run. The performance of the two most highly trained subjects is consistent with previous experimental results that indicate an incomplete trading of interaural time and intensity information. The subjective perceptions of these observers are not consistent with previous studies that describe a "time image" and a "time-intensity traded" spatial image.

Acoustic Stimulation↗

PubMed1978

Theory of binaural interaction based on auditory-nerve data. III. Joint dependence on interaural time and amplitude differences in discrimination and detection.

This paper is primarily concerned with issues of symmetry-asymmetry in the joint dependence of binaural performance on interaural time delay and interaural amplitude ratio. The predictions of our model based on auditory-nerve data are shown to be inadequate for available data showing asymmetries in interaural time discrimination. Measured detection thresholds for a 500-Hz tone burst masked by wide-band noise are reported for nonunity amplitude ratios and both polarities of delays in order to test for asymmetries analogous to those observed in the time discrimination case. The detection results show only small asymmetries and are not inconsistent with the model. A general discussion of our model and the implications of available empirical results leads to a suggested modification of the model. We show by an example that modifications of the type we are suggesting are capable of describing the detection data and at least the gross trends of the discrimination data.

Auditory Perception↗