In a choice RT task, 64 Ss pressed either a right-or left-hand key in response to directional commands provided by 400 and 1000 cps tones. On monaural trials, RT was significantly faster when the meaning of the tonal command corresponded with the ear in which it was heard (corresponding trials) than when it did not (noncorresponding trials). A comparison of monaural with binaural RT indicated that this Tonal Command X Ear Stimulated interaction was due to interference on the noncorresponding monaural trials rather than facilitation on the corresponding trials.
Rather than having a fixed level, Im, of the masking stimulus (masker) and varying the level, Is, of the masked stimulus {signal) until the signal was just detectable, Is was fixed and Im was varied until the signal was just detectable. In addition, the frequency of the signal, fs, was fixed, but the frequency of the masker, fm, was varied systematically for each given fs. Stimulus interaction was minimized by keeping Is low. Minimum Im for signal threshold was obtained when fm approximated fs. Also in general less Im was required to mask the signal if fm < fs as compared to fm > fs, where |fs − fm| is equal in both cases. Several other results were somewhat unexpected. If the frequency characteristics of masking are regarded as reflecting the “filter” characteristics of the ear then the attenuation vs frequency plot of these filters is quite uniform with center frequencies from 400 to 6400 cps. Using low Is the cutoff on the high frequency side is quite sharp with a 130–140 db per octave slope over at least a 70 db range and an indication that it may be still steeper at higher Is. An interesting irregularity appears on the Im for masking vs fm plots in the form of a notch when 0.8fs < fm < 0.9fs.
Current understanding of the relation monaural estimates of the critical bandwidth for masking and those obtained in binaural listening situations is poor. The present study was designed to improve this situation by obtaining estimates of critical bandwich when the signal and masker were presented: (1) monaurally (NmSm), (2) binaurally with both signal and masker in phase at the ears (NoSo), (3) binaurally with masker in phase and signals 180 degrees out of phase (NoSpi). Threshold estimates were obtained in a two-interval forced-choice paradigm as a function of masker bandwidth for signal frequencies of 500 and 2000 Hz for the three conditions mentioned above. Maskers were computer-synthesized and had essentially infinite rejection slopes. For all conditions, as masker bandwidth was narrowed from wide band, threshold remained relatively constant until some critical bandwidth was reached. Further reductions in bandwidth were followed by progressive lowering of threshold, presumably due to removal of masker energy in the critical band. For both signal frequencies, the derived critical bandwidth estimates for the NmSm and NoSo conditions were similar and were smaller than the critical bandwidth estimates obtained in the NoSpi condition.
Ten subjects were asked to produce octave judgments, i.e., one octave above and one octave below a standard stimulus, with bands of low-pass and high-pass noise as well as sinusoids. For example, given a specific low-pass noise band as a standard, subjects adjusted the cutoff frequency of a second low-pass noise band so that its pitch was 1 oct above that of the standard. Results indicate that bands of noise have a pitch and that the pitch is correlated with cutoff frequency. For low-pass noise, there seemed to be a relatively linear relation between pitch and cutoff frequency from 80- to 10 000-Hz cutoff, whereas the linear relation for high-pass noise holds only for a restricted frequency range, 600–10 000 Hz. The pitch of both types of noise stimuli degenerates above 10 kHz, possibly because of limited earphone response and a rising threshold of hearing. More difficult to explain is the static and vague pitch of high-pass noise at low cutoff frequencies. A discussion of several mechanisms is included.
The purpose of this study was to determine whether the auditory perceptual abilities of children are characterized by an age-related improvement in duration discrimination. Forty children, ages 4 to 10 years, and 10 adults served as subjects. Difference limens were obtained using a 350-msec broadband noise burst as the standard stimulus in a three-interval forcedchoice paradigm. Data were characterized by significant differences between the performances of the 4-, 6-, and 8-year-olds and those of the adults. Acquisition of adult-like discrimination performance was demonstrated between the ages of 8 and 10 years.
In a choice reaction time (RT) task, 5s pressed either a right-or lefthand key in response to monaural "right" and "left" commands conveyed by 200-and 500-IIz. 96-db. SPL tones. The commands were either presented alone (no-noise trials) or accompanied by a broad-band noise to the same or opposite ear. On the no-noise trials, RT was significantly faster when the meaning of the command corresponded to the ear in which it was heard than when it did not. This Tonal Command X Ear Stimulated interaction was eliminated, reduced, or reversed by manipulating the noise intensity at the opposite ear, and was accentuated by introducing accompanying noise to the same ear. Results are explained in terms of a potent natural tendency to react toward the major source of stimulation.
Reactions to biuaural tonal commands signifying "right" or "left" were significantly slowed when the meaning of the command conflicted with its apparent source. Manipulation of relative phase of the tones at the ears provided the means of altering the apparent source of the command as well as the strength of the irrelevant directional cue. Results indicated that the stronger the directional cue, the greater the interference with information processing.This study was concerned with increasing our understanding of a potent stereotype which interferes with the processing of information from certain auditory and visual displays. This stereotype, a strong initial tendency to react to the source rather than to the meaning of a stimulus, was first discovered in a study of reaction time (RT) to verbal directional commands (Simon & Rudell, 1967). The 5s pressed left-or right-hand keys in response to commands of "left" or "right" which were presented to the left or right ear. RT was significantly slower when the content of the command did not correspond with the ear stimulated (i.e., "left" in right ear or "right" in left ear) than when it did (i.e., "left" in left ear or "right" in right ear).Subsequent findings demonstrated that the phenomenon was not related to ear stimulated as such, but rather to the irrelevant directional cue associated with ear stimulated; i.e., the same phenomenon was observed when the apparent perceptual source of a binaural tonal command was manipulated by shifting the interaural phase (Simon, Small, Ziglar, & Craft, 1970). The interference produced by manipulating interaural phase was, however, not as conspicuous as that observed with monaural stimulation, presumably because the irrelevant directional cue produced by the particular phase-shift conditions used was not as potent as that produced by monaural stimulation. The purpose of the present study was to use interaural phase shift as a means of manipulating not only the spatial locus of a. stimulus but also the potency of the directional cue. If a directional cue was, in fact, responsible for the interference with information processing observed in previous studies, then it should be possible, by varying the strength of this irrelevant cue, to alter the amount of interference.Experiment I.-The apparatus provided a measure of choice RT to a series of binaural tones presented to S through Telephonies TDH-39, 300-ohm earphones mounted in NAF-48490-1 cushions and fixed to a standard headband. The S's task was to press the correct one of two finger keys as quickly as possible after hearing the tone. A Hunter Kloc-1 Requests for reprints should be sent to J.
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