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Biomedical subjects

W Jesteadt

Publications and source records attributed to W Jesteadt.

At least 37 records · Page 2Linked to original sources
PubMed1988

Latency of auditory brain-stem responses and otoacoustic emissions using tone-burst stimuli.

A comparison of the latency of auditory brain-stem responses (ABR) and evoked otoacoustic emissions (EOAE) has led to an interpretation for the travel of transients in the peripheral auditory system that is consistent with both sets of data. The "cochlear echo" theory for the origin of the EOAE indicates that the latency of a particular frequency component back to the ear canal should be twice the forward latency of its characteristic place in the cochlea. The latency of wave V of the ABR to tone-burst stimuli can be described as the sum of two components: (1) a component that varies with intensity and frequency in an orderly and predictable manner and (2) a component that is independent of both intensity and frequency. Because the EOAE data can be predicted by taking twice the value of component (1) of the ABR latency, this component is interpreted to be due to mechanical travel through the cochlea. A consequence of this interpretation is that the remaining neural component of the ABR latency must be relatively independent of frequency and intensity.

Acoustic Stimulation↗
PubMed1987

Auditory brainstem responses from graduates of an intensive care nursery: normal patterns of response.

Auditory brainstem responses (ABR) were obtained from graduates of an intensive care nursery (ICN) when those babies were in stable physiological states and ready for hospital discharge. Intensity ranged from ABR threshold to 80 dB nHL, and all recordings were made in a sound-isolated chamber. The data reviewed here are from 585 babies having presumably normal hearing, based upon bilateral ABR thresholds of 30 dB nHL or less. To insure that estimates of population statistics were not biased by high correlations between ears, only the data from the left ears were used in most analyses. Larger correlations were observed between conceptional age (CA) and ABR latencies than between either gestational age (GA) or chronological age (CHA) and the same latencies. Data were grouped into six CA groups for further analyses. Distributions of all response-component latencies were similar in shape and depended upon CA, showing orderly decreases in latency with increasing age. None of these distributions differed significantly from normal, and they were well fitted by normal ogives. Thus, accurate estimates of percentiles can be obtained from the means and standard deviations. The results indicate that it is important to take CA into account when evaluating ABR latencies.

Audiometry, Evoked Response↗
PubMed1987

Growth of masking as a measure of response growth in hearing-impaired listeners.

Growth-of-masking functions were obtained from 19 normal and 5 hearing-impaired listeners using a simultaneous-masking paradigm. When masker and probe frequency are identical, the slope of masking approximates 1.0 for both normal-hearing and impaired listeners. For masker frequencies less than or greater than probe frequency, the slopes for impaired listeners are shallower than those of normals. These findings are consistent with previously reported physiological data (single-fiber rate versus level and AP masking functions) for animals with induced cochlear lesions. Results are discussed in terms of a potential masking technique to estimate the growth of response in normal and impaired ears.

Adolescent↗
PubMed1987

Effects of pure-tone forward masker duration on psychophysical measures of frequency selectivity.

The effects of forward masker duration on psychophysical measures of frequency selectivity were investigated in two experiments. In both experiments, masker duration was 50 or 400 ms, signal duration was 20 ms, and there was no delay between masker offset and signal onset. In the first experiment, growth-of-masking functions were measured for a masker whose frequency was below, at, or above the 1000-Hz signal frequency. From those data, input filter patterns (IFPs) were plotted for masker levels from 40-90 dB SPL. In the second experiment, masking patterns (MPs) were measured for a 1000-Hz masker presented at 50, 70, and 90 dB SPL. Both measures of frequency selectivity (IFPs and MPs) indicate that frequency selectivity is greater for the 400-ms masker. These data suggest that there may be a sharpening of frequency selectivity with time at a stage prior to the adaptation observed in forward masking.

Adult↗
PubMed1986

Comparison of pure-tone audibility thresholds obtained with audiological and two-interval forced-choice procedures.

Audibility thresholds were measured at 500 and 4000 Hz with a standard clinical procedure and a two-interval, forced-choice (2IFC) adaptive procedure for 72 normal-hearing and hearing-impaired listeners, age 17 to 83. Psychometric functions were obtained for clinical, 2IFC, and Yes-No procedures. A measure of response bias was obtained from the Yes-No procedure. The 2IFC adaptive thresholds were 6.5 dB lower than audiological thresholds. The psychometric functions for the forced-choice procedures were generally shallower than those for the clinical procedure and were shifted to lower sound pressure levels. Response bias played a small role at best in accounting for the magnitude of the difference in threshold estimated by the adaptive and clinical procedures or for the differences among the psychometric functions.

Adolescent↗
PubMed1985

Speech perception ability and psychophysical tuning curves in hearing-impaired listeners.

Performance-intensity functions for monosyllabic words were obtained as a function of signal-to-noise ratio for broadband and low-pass filtered noise. Subjects were 11 normal-hearing listeners and 13 hearing-impaired listeners with flat, moderate sensorineural hearing losses and good speech-discrimination ability (at least 86%) in quiet. In the broadband-noise condition, only small differences in speech perception were noted between the two groups. In low-pass noise, however, large differences in performance were observed. These findings were correlated with various aspects of psychophysical tuning curves (PTCs) obtained from the same individuals. Results of a multivariate analysis suggest that performance in broadband noise is correlated with filter bandwidth (Q10), while performance in low-pass noise is correlated with changes on the low-frequency side of the PTC.

Adolescent↗
PubMed1985

The role of suppression in psychophysical measures of frequency selectivity.

The neural output of the cochlea consists of a structured spectral representation of the input waveform. Psychophysical studies of frequency selectivity provide measures of the quality of this spectral representation based on the detection of a spectrally narrow signal in the presence of competing acoustic inputs. Results are often interpreted in terms of the underlying physiological processes. The present paper begins with a summary of the basic principles and data and a review of recent efforts to extend the theoretical framework to account for a wider range of phenomena. It then discusses and evaluates specific assumptions concerning the role of suppression in psychophysical measures of frequency selectivity, an area of research that has received much attention in recent years. The goal is to provide a summary of current answers to basic questions at a time of rapidly expanding knowledge about both the physiology and psychophysics of frequency selectivity.

Animals↗
PubMed1984

Psychophysical tuning curves in normal-hearing listeners: test reliability and probe level effects.

Psychophysical tuning curves (PTCs) were obtained from 19 normal-hearing listeners using a computer-controlled, modified Bekesy tracking procedure which employed a minimum standard error stopping rule. Using an objective procedure, 2000-Hz PTCs were quantified on five dimensions (Q10, tip-to-tail difference, d1-oct, low-frequency slope, and high-frequency slope), and the test-retest reliability of each measure was assessed. To provide a basis for future comparisons between normal-hearing and hearing-impaired listeners, these measures were obtained as a function of increasing probe level.

Adult↗
PubMed1983

Additivity of forward masking.

Masked thresholds for a 1000-Hz sinusoidal signal were measured as a function of masker level in both forward and simultaneous masking for two types of maskers: a 1000-Hz sinusoid and a narrowband noise, 60-Hz wide, centered at 1000 Hz. In forward masking, the noise masker produced much steeper growth-of-masking functions than the sinusoid. Presenting a contralateral broadband noise "cue" with the forward masker dramatically reduced the slope of masking for the noise masker but did not influence results for the sinusoidal masker. The noise remained the more effective masker. The amount of masking produced by combinations of equally effective narrowband-noise and sinusoidal maskers was compared to that produced by each masker individually with and without the contralateral cue. No additional masking beyond that predicted by energy summation was measured for forward masking. Additional masking beyond energy-sum predictions was measured for analogous conditions in simultaneous masking. Comparisons of results obtained with and without the contralateral cue suggest that signal thresholds in the presence of narrowband-noise forward maskers can reflect nonperipheral auditory processes.

Acoustic Stimulation↗
PubMed1982

Forward masking as a function of frequency, masker level, and signal delay.

The forward masking of a sinusoidal signal by a sinusoid of the same frequency was investigated for frequencies ranging from 125 to 4000 Hz. Forward masking in dB is proportional to both masker level and log signal delay at each frequency. More forward masking occurs at very low frequencies than at high frequencies, given equal-sensation-level maskers, and masked thresholds are greater at low frequencies than at high frequencies given equal-SPL maskers. The data can be described equally well by assuming that the difference in forward masking as a function of frequency is due to a change in the time course of recovery from masking or to a change in the growth of masking at each signal delay. The frequency effect is not large enough to change the interpretation of forward-masking data in studies of suppression or psychophysical tuning curves.

Adult↗
PubMed1982

A signal-detection-theory measure of pitch shifts in sinusoids as a function of intensity.

Pitch shifts in sinusoids as a function of intensity result in systematic response biases and differences in performance in forced-choice frequency-discrimination tasks. Two approaches are described for converting these effects to a measure of pitch shift in Hz using standard signal-detection-theory assumptions. To illustrate these approaches, forced-choice frequency-discrimination data were obtained for three listeners at 250 and 4000 Hz, with six intensities from 40 to 90 dB SPL. The resulting pitch-shift estimates are in good agreement with adjustment data obtained from the same listeners. Collection and analysis of the forced-choice data can be greatly simplified by using an adaptive procedure. Pitch-shift estimates obtained in this way for two of the three listeners are in good agreement with the other estimates.

Adolescent↗
PubMed1977

Sequential effects in judgments of loudness.

A multiple regression analysis of sequential effects in magnitude estimation and absolute identification is presented as an alternative to the approach used by Lockhead and his students. The new analysis indicates that sequential effects do not extend over more than one trial. This is in agreement with the response ratio hypothesis. A more detailed multiple regression analysis of these sequential effects indicates that the magnitude of the correlation between successive responses is heavily dependent on the decibel difference between successive signals. This is not in agreement with the response ratio hypothesis, and the hypothesis is reformulated to take account of this finding. This modification of the model is tested by comparing distributions of normalized responses to theoretical distributions suggested by the model and to a possible alternative distribution.

Acoustic Stimulation↗
PubMed1976

Temporal acuity in listeners with sensorineural hearing loss.

Temporal acuity, the minimum time interval within which the auditory system can discriminate the order of auditory events, was measured for three listeners with normal hearing and for 10 listeners with sensorineural hearing loss. Eight of the 10 listeners with sensorineural loss showed better temporal acuity for conditions with greater loss. The remaining two listeners showed the opposite effect. The temporal acuity results are not well correlated with either speech discrimination scores or measures of recruitment. The temporal acuity results do appear to be correlated with results observed in studies of temporal integration or brief-tone audiometry. Listeners with sensorineural loss tend to have both poor temporal integration and good temporal acuity. This suggests that the two temporal measures may reflect a single time constant in the auditory system.

Adult↗