Auditory Trains Research Articles

Can the Binaural System Preserve Temporal Information for Detection of Jitter?

Thresholds for the detection of temporal irregularity or “jitter” were obtained under three conditions: (1) monaural presentation of auditory pulse trains; (2) binaural presentation of auditory pulse trains, where the pulses were randomly assigned to the two ears; and (3) monaural presentation of one of the binaural channels of Condition 2. Since the binaural system shows microsecond sensitivity to temporal differences for lateralization, might not the binaural system preserve temporal information for the judgment of jitter? If the binaural system preserved temporal information prior to the analysis of jitter, thresholds under Conditions 1 and 2 would be equivalent, and both would be superior to Condition 3. In fact, Conditions 2 and 3 yielded nearly equivalent thresholds and both were substantially inferior to Condition 1. This result suggests that the binaural system does not preserve temporal information in a manner that permits acute temporal resolution for discrimination of jitter. [This research was supported in part by a grant from National Science Foundation.]

Effect upon auditory interval discrimination by perturbations in the nanosecond region

A temporal uncertainty, or jitter, of less than 200 nsec in the intervals of an auditory pulse train significantly raises the interval (pitch) discrimination threshold. The results suggest a preneural, i.e., cochlear, analysis for high frequency auditory pulse trains.

Discrimination of mean temporal interval within jittered auditory pulse trains.

Thresholds for the auditory discrimination of mean interpulse interval were determined as a function of the number of intervals and of temporal variability, or “jitter.” Interval discrimination at low pulse frequencies is relatively independent of the number of pulses and of jitter. By contrast, interval discrimination at high pulse frequencies is extremely dependent upon the number of pulses and the level of jitter. The precision of interval discrimination achieved suggests that pulse interval discrimination for high pulse frequencies is carried out by a spectral analysis, rather than by a temporal analysis, of auditory information.

Periodicity discrimination for auditory pulse trains.

Two forms of periodicity are distinguished for auditory pulse trains in which information is coded in terms of the interval between successive pulses. Internal periodicity refers to the precision of reproducing adjacent intervals between successive pulses. External periodicity refers to the reproduction of a repeated pattern of successive pulses. Two variables were manipulated to study the discrimination of pulse trains of controlled internal and external periodicity: the number of successive presentations of a given pattern of interpulse intervals and the deviation of the intervals from strict internal periodicity. Equivalent results are obtained with both variables. Periodicity discrimination improves as the number of interpulse intervals within the pattern is increased and as the average interpulse interval is decreased. Acute periodicity discrimination is developed at high pulse frequencies with a large number of interpulse intervals. Periodicity discrimination at low pulse frequencies is relatively poor and is relatively independent of the number of interpulse intervals. Two quantitative models, based upon informational measures, are examined with respect to their rank orderings of conditions for auditory periodicity discrimination.

Detection and relative discrimination of auditory "jitter".

Thresholds for the minimal departure from periodicity and thresholds for discrimination of relative departures from periodicity were obtained in order to explore the limits of temporal resolution for auditory pulse trains. In a forced-choice test, listeners were presented pulse trains, one of which was subjected to more variability, or “jitter,” than the other three. His task was to select that pulse train that was different from the other three. The principal experimental variables examined were: the number of intervals; the mean interpulse interval; and, the jitter of the reference pulse train. Minimum thresholds for jitter, relative to the center interpulse interval, are less than 0.1% for large number of pulses. Threshold jitter decreases with shorter interpulse intervals for a large number of pulses. Jitter thresholds are minimal for interpulse intervals of 4–6 msec for a small number of pulses. Jitter discrimination is approximately independent of the reference jitter for a small number of pulses and is nearly directly proportional to the reference jitter for a large number of pulses. The temporal precision of the auditory system, in contrast to its precision of spectral analysis, appears to be insufficient to account for minimal jitter thresholds.

Number or duration discrimination for auditory pulse trains.

Number or duration discrimination for auditory pulse trains.

Detection and Relative Discrimination of Auditory “Jitter.”

Thresholds for the minimal departure from periodicity and thresholds for discrimination of relative departure from periodicity were obtained in order to explore the limits of temporal resolution for auditory pulse trains. In a forced-choice test, listeners were presented pulse trains, one of which was subjected to more variability, or jitter, than the other three. The principal experimental variables examined were: the number of intervals; the mean interpulse interval; and, the jitter of the reference pulse train. Minimum thresholds for jitter, relative to the center interpulse interval, is less than 0.1% for a large number of pulses. Threshold jitter decreases with shorter interpulse intervals for a large number of pulses. Jitter thresholds are minimal for interpulse intervals of 4–6 msec for a small number of pulses. Jitter discrimination is approximately independent of the reference jitter for a small number of pulses and is nearly directly proportional to the reference jitter for a large number of pulses. The temporal precision of the auditory system, in contrast with its precision of spectral analysis, appears insufficient to account for minimal jitter thresholds.