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D R Perrott

Publications and source records attributed to D R Perrott.

At least 37 records · Page 2Linked to original sources
PubMed1987

Changes in head position as a measure of auditory localization performance: auditory psychomotor coordination under monaural and binaural listening conditions.

Two experiments examined the capacity of listeners to turn and face an active sound source. Tests were conducted with sources located in the subject's forward field (an arc extending from 60 degrees to the subject's right to 60 degrees to the left). Localization performance was determined under both monaural and binaural listening conditions, using both brief pulses and sustained pulse trains as target signals. Not unexpectedly, the ability to orient the face to a hidden sound source was very poor under monaural conditions if the listener received only a brief (100-ms) tonal pulse. When continuous pulse trains were employed, localization, even under monaural conditions, became quite accurate. Across conditions, this complex motor response produced results in agreement with those that have been obtained when subjects were only required to report their spatial impressions. In particular, performance with binaural pulse trains was observed to vary as a function of the frequency of the target signals employed. Descriptions of the head movement response, along with a discussion of some of the implications of ear-head coordination, are presented.

Auditory Perception↗
PubMed1987

Conditions under which the Haas precedence effect may or may not occur.

This investigation explored the stimulus conditions of the existence region in the free field of the Haas "precedence" effect. Experienced normal-hearing adults (N:5) listened to 50-msec bursts (0.2 msec rise-fall) of broadband noise from 2 loudspeakers at 1 m distance at ear level, at +/- 20 degrees re midline. Bursts from the loudspeakers were separated by interstimulus onset intervals (ISO-Is) between 0 and 50 msec. In one condition, uncorrelated noise was produced by separate generators; in a second condition (correlated noise), the signal from one generator was split and led to each speaker. Ss classified their experience of each presentation into one of five defined categories:: (1) single non-moving sound image; (2) 2 stationary but spatially distinct sound images; (3) single sound moving from lead to lag source; (4) as (3) but motion interrupted or broken; and (5) 2 successive sound images, with no apparent motion. In addition, Ss indicated direction (L-R; R-L) of any apparent motion. At 0 msec ISOI, directional judgments with either correlated or uncorrelated bursts were at or near chance level, as expected, and with correlated noises a single image was usually (71%) experienced, presumably at an apparent location at or near the midline. But with uncorrelated noises, 2 simultaneous but distinct sound images were usually (68%) perceived. At 2 msec ISOI, a weak precedence effect was exhibited for correlated noise, where the "single" response was often (55%) made; but even here the effect of the second burst was not "suppressed" entirely since direction judgments were 83% accurate. At 4 msec ISOI, "single" responses had declined to 36% for correlated and to 6% for uncorrelated noises, while by 8+ msec, "single" responses were dominated more or less completely by perceptions of dual sources. We conclude that the precedence effect is often confined to extremely brief ISOIs, and that the parameters of stimulus duration and complexity, of rise-fall times, absolute placement and angular separation of sound sources, subject differences, and a variety of types of perceptual experiences need to be addressed experimentally before the existence region of the precedence effect is well defined or uncritically accepted; and that it is too soon to attempt to posit neurophysiological mechanisms in explaining the phenomenon.

Acoustic Stimulation↗
PubMed1984

Concurrent minimum audible angle: a re-examination of the concept of auditory spatial acuity.

Minimum audible angle was measured for simultaneous acoustic events. Localization of concurrent events was found to be a direct function of the spectral differences between the events, the angle between the sources, and the location of the sources within the field defined by the subject. In the latter case, the m.a.a. was smallest with sources placed symmetrically about the listener's median plane and maximal at the extreme lateral portions. Post-hoc tests were completed which indicate that the spectral limits for concurrent localization is dependent both upon the angular separation of the sources and the position within the field as defined by the locus of the subject. The functions obtained approach the values reported by Mills [J. Acoust. Soc. Am. 30, 237-246(1958)] as the temporal overlap between the concurrent events decreased. The present results suggest that a single localization function may exist with the optimal performance observed with fully successive stimuli and poorest performance in the condition involving simultaneous events. The implications of these results are discussed.

Auditory Perception↗
PubMed1984

Discrimination of relative distance in the auditory modality: the success and failure of the loudness discrimination hypothesis.

Difference limens for auditory distance discrimination were determined using the method of limits. Eight untrained subjects were tested across a wide range of distances (49 to 4876 cm) using broadband noise sources. For sources in excess of 304 cm, the Weber ratios observed approximated the function predicted by the inverse first power loss equation. At the longer distances, the subjects appear to be judging distance on the basis of the loudness difference cue. At the shorter distances (49 to 304 cm), the Weber ratios were considerably larger than would be predicted from the inverse first power loss equation. In this range, distance discrimination becomes increasingly degraded as the referent source approaches the subject.

Adult↗
PubMed1984

Discrimination of the spatial distribution of concurrently active sound sources: some experiments with stereophonic arrays.

Several experiments are described in which subjects were required to discriminate differences in the spatial distribution of concurrently active sound sources in stereophonic arrays. For pure tone stimuli and binaural listening, systematic discrimination functions were observed when relatively small intersource frequency differences (approximately 30 Hz) were present. For tonal stimuli, this discrimination task was reliably performed only for frequencies below 1500 Hz. Additional tests were conducted with amplitude-modulated tonal stimuli, low- and high-frequency uncorrelated noise, correlated low-frequency noise, and, with the uncorrelated low-frequency noise, for stimuli presented in both the vertical plane and under monaural listening conditions. The results of all of these manipulations support the notion that the spatial distribution of sources in a stereophonic array can be appreciated if disparate low-frequency energy is available from the sources in a horizontal configuration. The implications of these results are discussed relative to acoustic processing in the natural environment.

Auditory Perception↗
PubMed1982

Judgments of sound volume: effects of signal duration, level, and interaural characteristics on the perceived extensity of broadband noise.

While auditory stimuli are often described in terms of their apparent extensity, such descriptions have usually not been collected systematically. Moreover, the few deliberate attempts to evaluate image size have rarely gone beyond the classic parameters of stimulus frequency and intensity. In the present study a direct magnitude estimation procedure was employed. Seventeen subjects numerically estimated the apparent size of images produced by broadband noise stimuli. Under earphone listening conditions, signals were presented either dichotically (uncorrelated noise), diotically (correlated noise), or monaurally (noise led to a single earphone). The signals in each of these modes varied in duration (100, 300, 1000, and 3000 msec) and intensity level (60, 75, and 90 dB A weighted). Size estimates were plotted as power functions and analyzed with a repeated measures design analysis of variance. Consistent with previous research, the main effects of duration and intensity were both highly significant (p less than 0.001). In addition, a highly significant effect for mode of presentation was found (p less than 0.001). Across conditions, dichotic stimulation produced the largest images and monaural stimulation the smallest (about half the size of the diotic images). This last result is the first quantification of previous anecdotal observations. General implications of these results were discussed.

Ear↗
PubMed1981

Dynamic minimum audible angle: binaural spatial acuity with moving sound sources.

This study examined in 4 normal-hearing young adults the effects of motion of the sound source upon the accuracy of auditory localization. S controlled the initiation of the energizing of a small loudspeaker on a rotating boom overhead such that the initiation of a brief tonal pulse at .5 kc/s was perceived to be at S's 0 degrees azimuth (a small light was a visual referent). Pulse duration was either a constant 80 msec or a constant arc (19 degrees). Minimum audible angle (m.a.a.) was taken as the standard deviation of a distribution of 10 judgments per set of conditions. A significant increase in m.a.a. occurred at the highest velocity (240 degrees/sec), but at slower velocities the m.a.a. was nearly identical (approximately 1.0 degrees) to that of earlier research using stationary sources. While motion appears to have a minimal effect on localization precision as defined here, large constant errors were observed in the apparent position of the source at onset as function of velocity. With moving sources, Ss experienced an apparent shift of the auditory image in the direction of motion. For constant pulse duration, shifts were 5.2, 5.6, 7.0, and 12.3 degrees, and for constant arc 8.7, 9.2, 9.9, and 11.2 degrees, at velocities of 45, 60, 120, and 240 degrees/sec, respectively. The present results indicated that the thresholds associated with the detection of motion (minimum audible movement angle, m.a.m.a.) and with binaural spatial resolution (m.a.a.) are probably independent. This, in turn, suggests that selectively tuned "motion detectors," analogous to the neurons described in the visual literature, may be present in the auditory system.

Adult↗
PubMed1979

Dynamic auditory localization: systematic replication of the auditory velocity function.

Two experiments explored the capability of normal-hearing adults to judge the apparent velocity of an unseen moving sound source. In exper. I, 9 naive and, 1 experienced S judged the velocity of a moving source emitting a .5-kc/s tone at 50 db SPL. S's head was in the center of a circle of 1.88-m radius swept by a small loudspeaker. In exper. II the sound was a low-pass-filtered (0.1-1 kc/s) noise at 50 db sound spectrum level. In both experiments perceived velocity was directly proportional to the actual velocity of the source. These results support out initial observations (Waugh et al, J. Aud. Res., 1979, 19, 103-1 10) that auditory velocity discrimination can be described as a power function with an exponent of 1.0. In exper. II the Ss also varied the sound source velocity by means of a variable resistor to produce a perceived velocity of 100 degrees/sec. Performance on the adaptive velocity production task was successfully predicted from the data of the absolute velocity judgment task. The Weber fraction was .052 for relatively fast-moving sound sources (100 degrees/sec). The ability to discriminate sound source velocity appears to be a well-defined feature of the dynamic binaural spatial system.

Audiometry↗
PubMed1979

Perception of moving sounds: velocity discrimination.

Two experiments investigated auditory velocity perception. Exper. I compared auditory to visual velocity estimates. Five adults judged, in miles/hr, the motion of a sound source (a small loudspeaker) moving on a 1.88-m boom around S's head at each of 7 velocities from 15 to 360 degrees/sec. The sound source was either visible or not visible. Velocity judgments were shown in both modalities to be a power function of source velocity, with a slope of approximately 0.90. No significant difference was found between the auditory and visual functions. A control Exper. II determined with 14 naive adults that the similarities between the functions in each modality could not be attributed to either previous visual experience or proprioceptive feedback. Ss estimated the velocity of the visible moving loudspeaker while tracking the source with their eyes (N: 7) or while fixating on a small stationary light (N: 7). Eye motion was recorded from electrodes on the canthi. No significant differences were found between these conditions. The estimates were again shown to be a power function of source velocity (though slightly higher slopes of 0.99 for visual pursuit and 1.0 for visual fixation were obtained than in Exper. I). These experiments suggest a surprising degree of similarity in the perception of velocity in auditory and visual spatial functions.

Adult↗
PubMed1978

Backward masking: detection versus recognition.

The backward detection masking of 10-ms tonal targets by a 150-ms tonal mask was contrasted with the backward recognition masking of the same tones by the same mask. The target-mask interval required for 75% correct performance was about eight times as great in the recognition condition as in the detection condition. Furthermore, a generalized improvement in performance occurred over the initial course of training in both the detection and recognition conditions. In a second experiment it was found that a remote mask produced greater backward recognition masking but less backward detection masking. That these differences were observed with the same subjects, at the same level of training, and with identical stimuli, indicates that procedural differences alone cannot account for the differences between backward detection and recognition masking.

Discrimination, Psychological↗
PubMed1977

Minimum auditory movement angle: binaural localization of moving sound sources.

In the first experiment, subjects were asked to discriminate whether a sound was emanating from a moving or stationary source. The minimum audible movement angle (MAMA) thus defined was observed to increase as the source velocity increased. MAMA ranged from a low of 8.3 degrees with the slowest velocity employed (90 degrees/s) to a high of 21.2 degrees with the fastest velocity (360 degrees/s). In the second experiment, subjects were asked to localize where the moving source was, at signal on and offset. The results indicate that the apparent onset is displaced in the direction of motion and the amount of this displacement is directly related to source velocity. Less consistent results were observed with signal offset. The present results suggest that the binaural system is relatively insensitive to motion.

Adult↗