Lloyd F. Elfner

Continuity in Alternately Sounded Tonal Signals in a Free Field

An experiment is reported that employed 20 normally hearing listeners who demonstrated an ability to concentrate on an interrupted signal that alternated with a shorter, more intense signal. The purpose of the study was to investigate the effects of the frequency relationship between the two components, to determine the effect of angular separation of the two components, and to demonstrate continuity effects in a free field. The results indicated a definite frequency effect and a significant though small effect due to angular separation on the continiuty threshold.

Gap detection with three auditory events—a single‐channel process

Temporal resolution of a silent interval (gap) imbedded in a three‐tonal‐pulse train was investigated. Two frequencies were alternated in a three‐event array where the gap could appear between the first and second or second and third auditory event. Frequency and gap position effects were systematically explored using a temporal two‐interval forced‐choice paradigm and a modified tracking procedure. Gap detection was found to vary as a function of antecedent event duration and signal‐comparison stimulus similarity. Indications of a filter process similar in bandwidth to the empirical critical band was found in fully correlated signal‐comparison stimulus conditions. Obtained results are consistent with fixed‐filter signal‐envelope detection models found in the simultaneous and forward‐masking literature.Subject Classification: [43]65.75, [43]65.68.

Temporal and Intensive Factors in Binaural Lateralization of Auditory Transients

The present experiment employed three experienced listeners. The primary purpose was to investigate the ability of the listener to detect a just noticeable shift from center of a dichotically produced auditory image. Thresholds were determined using a modification of Fechners Method of Right and Wrong Cases. Thresholds were evaluated by means of an oscilloscope and camera. All combinations of a 600‐Hz and a 6000‐Hz tone and rise times of 10, 50, and 250 msec were used. Individual threshold plots are shown for each experimental condition. Tables are presented showing the intensity levels of the lead signal and the intensity differences between the two signals during the rise‐time portion of the signal complex for the various values employed. A frequency‐dependent relationship was indicated only for the 10‐msec rise‐time signal. It was also noted that time differences between equal intensity portions (of the two signals) are not constant throughout the rise time of the signals.

Lateralization and Intensity Discrimination

This study reports the effects of various binaural intensity patterns on the discrimination of changes in the position and intensity of binaurally induced auditory images. The difference limen obtained for just‐noticeable shift of an auditory image is in most cases not significantly different from the difference limen observed in discrimination of a just‐noticeable change in the intensity of the signal. Only under low intensity levels is such a difference noted. Significant effects are observed as a function of the binaural intensity pattern employed. Also an increase intensity of the signal invariably produced a smaller just‐noticeable difference than a decrease in the intensity of the signal. A functional relationship is indicated between image movement and sensitivity to intensity change.

Some Factors Affecting the Perception of Continuity in Alternately Sounded Tone and Noise Signals

Three experiments are reported that employed 78 normally hearing college students who demonstrated an ability to concentrate on an interrupted white noise that alternated with a tonal burst. The purpose of these experiments was to investigate the effects of the duration of the white noise and the frequency of the tonal burst on the perception of continuity under monaural and dichotic presentation. The effect of the number of noise pulses in the stimulus interval was also investigated. The results showed that under monaural presentation the perception of continuity was affected by both the duration of the noise and the frequency of the tone. Only the duration variable was significant under dichotic presentation. The number of noise pulses in the stimulus interval significantly affected the perception of continuity.

Autokinetic Enhancement as a Function of Flicker

The apparent movement of a stationary spot of light on a homogeneous background is perceived with shorter latency and greater spatial displacement when the spot is flickering than when fused. The enhancing effect of flicker is more pronounced for females than males. There is a significant difference in the latency of the apparent movement between the sexes. Response measures of latency and spatial displacement of autokinesis show a positive relationship.

Continuity effects with alternately sounding tones under dichotic presentation

An experiment is reported in which 10 Ss possessing normal hearing were required to make discriminations of continuity or interruption in a longer less intense signal (Tone A) which alternated in time with a shorter more intense signal (Tone B). The signals were presented dichotically with Tone A at the right ear. Three Tone B frequencies of 300, 1000, and 4000 cps and five Tone A frequencies somewhat near each of the Tone B frequencies were employed. The results demonstrated that as Tone A was nearer to Tone B in frequency, continuity thresholds in Tone A occurred at longer durations of Tone B. The results are discussed in terms of a central neural model.

Auditory Continuity Effects as a Function of the Duration and Temporal Location of the Interpolated Signal

The present experiment employed 20 college students who demonstrated an ability to make determinations of interruption or continuity in a random noise signal that alternated with a tonal burst. The primary purpose of this experiment was to investigate the effects of the duration the temporal location of the interpolated signal on the perception of continuity under monaural presentation. The effect of frequency of the interpolated tone was also evaluated. The results showed that the perception of continuity in the noise was affected by both the duration and frequency of the interpolated tonal signal. The location of the interpolated signal had no significant differential effect on continuity thresholds.

Effect of Prolonged Exposure to a Binaural Intensity Mismatch on the Locus of a Dichotically Produced Tonal Image

An experiment is reported on the effect of six consecutive 21‐min periods of exposure to frequencies of 700, 1000, or 3000 cps, dichotically presented with a 50‐dB interaural intensity imbalance, on the subsequent locus of the dichotically produced auditory image of the same frequencies. Significant differences in the locus of the auditory image were found among the test frequencies. There was a differential effect on the locus of the image of the test frequencies as a function of the frequency of the saturation tone. No significant changes were noted in the sensitivity of the auditory system to the frequencies employed. No changes in pitch were reported, although preexperimental instructions did not direct attention to this phenomenon. The results are discussed in terms of several theoretical models for localization.

Lateralization of pure tones as a function of prolonged binaural intensity mismatch

Pre-exposure of the right ear to amplification of auditory input by means of a hearing aid produced decrements in the ability to lateralize pure tones under dichotic presentation. The decrement in lateralization function increased with an increase in pre-exposure duration. Lateralization decrement was not affected by the signal frequency.