Richard E. Pastore

Perception of acoustic source characteristics: Walking sounds

The current study investigated the ability of subjects to perceive source characteristics (the gender of a human walker) of a naturally occurring auditory event (human walking). A number of acoustic properties were measured and subjected to statistical analyses in order to identify those properties that differentiate male and female walking footsteps. A principal component analysis on the statistical properties of the spectral energy distributions then identified two classes of information that were important in determining subject perception of the gender of a walker: (1) the spectral peak which integrates the information about the spectral central tendency of frequency and shape of the spectral peak; and (2) the contribution of high-frequency spectral components. A follow-up experiment then manipulated these spectral properties to verify their contributions in the perceptual classification of walker gender. Additionally, the effect of shoe on the gender judgement in walking sequences was assessed by having both male and female walkers wear males shoes.

Relative Effectiveness of Three Stimulus Variables for Locating a Moving Sound Source

A study is reported in which it is shown that observers can use at least three types of acoustic variables that indicate reliably when a moving sound source is passing: interaural temporal differences, the Doppler effect, and amplitude change. Each of these variables was presented in isolation and each was successful in indicating when a (simulated) moving sound source passed an observer. These three variables were put into competition (with each indicating that closest passage occurred at a different time) in an effort to determine their relative importance. It was found that amplitude change dominated interaural temporal differences which, in turn, dominated the Doppler effect stimulus variable. The results are discussed in terms of two interpretations. First, it is possible that subjects based their judgements on the potential discriminability of each stimulus variable. However, because the stimuli used involved easily discriminable changes, subjects may instead have based their judgements on the independence of a stimulus variable from different environmental situation conditions. The dominance ordering obtained supports the second interpretation.

“Nonparametric”A’ and other modern misconceptions about signal detection theory

Many modern descriptions of signal detection theory (SDT) are, at best, distorted caricatures of the Gaussian equal-variance model of SDT (G-SDT). The distortions have sometimes led to important, but unwarranted, conclusions about the nature of cognitive processes. Some researchers reject using ď and β because of concerns about the validity of explicit underlying assumptions (that are shared with most inferential statistics), instead using either the supposedly “nonparametric” measures ofA′ andB″ or measures known to confound ability and bias. The origins, development, and underlying assumptions of SDT are summarized, then contrasted with modern distortions and misconceptions. The nature and interpretation of common descriptive statistics for sensitivity and bias are described along with important pragmatic considerations about use. A deeper understanding of SDT provides researchers with tools that better evaluate both their own findings and the validity of conclusions drawn by others who have utilized SDT measures and analyses.

Temporal order identification: Some parameter dependencies

Temporal order identification thresholds (TOT) for auditory stimuli have long been believed to be independent of the parameters of the stimuli as long as the judgment of order is (apparently) based directly upon the temporal difference rather than modality‐specific stimulus interactions associated with the temporal difference. We have found that TOT is a direct function of stimulus duration and, at least for longer rise times, is also a function of the rise time of the stimuli. Finally, adding a new tone to the end of the stimulus complex alters TOT only for short duration stimulus complexes. The relationship between TOT and the perception of speech stimuli contrasted in initial onset characteristics is discussed.

Evidence for auditory feature integration with spatially distributed items.

Recent auditory research using sequentially presented, spatially fixed tones has found evidence that, as in vision for simultaneous, spatially distributed objects, attention appears to be important for the integration of perceptual features that enable the identification of auditory events. The present investigation extended these findings to arrays of simultaneously presented, spatially distributed musical tones. In the primary tasks, listeners were required to search for specific cued conjunctions of values for the features of pitch and instrument timbre. In secondary tasks, listeners were required to search for a single cued value of either the pitch or the timbre feature. In the primary tasks, listeners made frequent errors in reporting the presence or absence of target conjunctions. Probability modeling, derived from the visual search literature, revealed that the error rates in the primary tasks reflected the relatively infrequent failure to correctly identify pitch or timbre features, plus the far more frequent illusory conjunction of separately presented pitch and timbre features. Estimates of illusory conjunction rate ranged from 23% to 40%. Thus, a process must exist in audition that integrates separately registered features. The implications of the results for the processing of isolated auditory features, as well as auditory events defined by conjunctions of features, are discussed.

Auditory event perception: The source—perception loop for posture in human gait

There is a small but growing literature on the perception of natural acoustic events, but few attempts have been made to investigate complex sounds not systematically controlled within a laboratory setting. The present study investigates listeners’ ability to make judgments about the posture (upright—stooped) of the walker who generated acoustic stimuli contrasted on each trial. We use a comprehensive three-stage approach to event perception, in which we develop a solid understanding of the source event and its sound properties, as well as the relationships between these two event stages. Developing this understanding helps both to identify the limitations of common statistical procedures and to develop effective new procedures for investigating not only the two information stages above, but also the decision strategies employed by listeners in making source judgments from sound. The result is a comprehensive, ultimately logical, but not necessarily expected picture of both the source—sound—perception loop and the utility of alternative research tools.

Duplex perception with musical stimuli

Duplex perception, a phenomenon previously demonstrated for speech stimuli, is demonstrated here for musical stimuli. In the first experiment, major and minor chords are produced by dichotic fusion of two simultaneous piano notes presented to one ear (perfect fifth) with a “natural” or “flat” single note presented to the opposite ear. Musically trained subjects perceive simultaneously both the single tone and a fused (major or minor) chord. The chords are labeled more consistently than the single notes, even though the fused chords differ solely in terms of the contralateral notes. In a second experiment, using pure tones in place of piano notes, other musically trained subjects individually exhibited categorical perception for either the fused chord or the single tones, but never for both types of stimuli. The duplex phenomenon is discussed in terms of its implications for its specific component modes of perception.

Change detection in multi-voice music: the role of musical structure, musical training, and task demands.

This study evaluated the relationship between primitive and scheme-driven grouping (A. S. Bregman, 1990) by comparing the ability of different listeners to detect single note changes in 3-voice musical compositions. Primitive grouping was manipulated by the use of 2 distinctly different compositional styles (homophony and polyphony). The effects of scheme-driven processes were tested by comparing performance of 2 groups of listeners (musicians and nonmusicians) and by varying task demands (integrative and selective listening). Following previous studies, which had tested only musically trained participants, several variables were manipulated within each compositional style. The results indicated that, although musicians demonstrated a higher sensitivity to changes than did nonmusicians, the 2 groups exhibited similar patterns of sensitivity under a variety of conditions.

MEASURING THE DIFFERENCE LIMEN FOR IDENTIFICATION OF ORDER OF ONSET FOR COMPLEX AUDITORY STIMULI

The approximately 20-msec perceptual threshold for identifying order of onset for components of auditory stimuli has been considered both as a possible factor contributing to the perception of voicing contrasts in speech and as no more than a methodological artifact. In the present research, we investigate the identification of the temporal order of onset of spectral components in terms of the first of a sequence of thresholds for complex stimuli (modeled after consonant-vowel [CV] syllables) that vary in degree of onset. The results provide clear evidence that the difference limen (DL) for discriminating differences in onset time follows predictions based on a fixed perceptual threshold or limit at relatively short onset differences. Furthermore, the DL seems to be a function of context coding of stimulus information, with both the DL and absolute threshold probably reflecting limits on the effective perception and coding of the short-term stimulus spectrum.

Temporal order judgment of auditory stimulus offset.

The temporal order judgment threshold for the offset asynchronies of pairs of tones at least 10 msec in duration was found to follow a pattern of parameter dependencies which is similar to that found for the onset of acoustic stimuli. Both thresholds increase with increased stimulus duration, but both appear not to depend upon the intensity or frequency of the component stimuli. Temporal order judgment thresholds for offset asynchronies appear to be briefer than onset asynchronies, probably due to the availability of some form of echoic information in the offset condition. Implications for models of temporal order perception and for the perceptions of temporally contrasted CV and VC syllables are discussed.