The effect of continuity on auditory stream segregation

Abstract

A rapid. repeating cycle of alternating high and low tones was presented under three conditions. In the "discrete" condition. transitions between tones were abrupt: in the "ramped" condition. successive tones were connected by frequency glides. In the "semiramped" condition. there were partial glides in frequency (as in speech). "Discrete" sequences were most likely to split perceptually into high and low streams, making order discriminations difficult. The "ramped" condition was least likely to split, and order perception was easiest. Results for the "semiramped" condition were intermediate. The discussion relates these findings to the acoustic properties of speech and to the process of auditory stream formation.Not long ago, Warren, Obusek, Fanner, and Warren (I969) reported what they perceived as a remarkable inability of unpracticed human Ss to make a judgment of order. The stimulus was a repeating cycle of four sounds: hiss, buzz, sine tone, and vowel, each lasting 200 msec, Few SS could name the order of the sounds.This struck them as puzzling in view of the already known capacity of the auditory system to discriminate the order of sounds at a much higher rate. For example, in normal English speech, phonemes occur more quickly-Bu-l Ou msec per phoneme (Efron, 1963). Speech can be reported correctly at rates as fast as 30 msec per phoneme (Foulke & Sticht, 1969). Winckel (1967) reports that temporal order of musical notes is resolvable down to about 50 msec per note. Warren et al (1969) found that the order of short repeating sequences of spoken digits was reported more accurately than unrelated sounds presented at the same rate, and concluded that verbal sounds were related in some fashion that permitted more rapid perceptual following. There is some confirmation for this in the work of Thomas, Hill, Carroll, and Garcia (1970), who found that the order of a repeating cycle of four vowel segments spliced together could be correctly identified at 125 msec per segment (but not at 100 msec per segment). Yet, even this rate is not as fast as we can discriminate the order of sounds in speech. Bregman and Campbell (1971) have proposed that the difficulty experienced by Ss in experiments using repeating cycles of sounds is due to the fact that subsets of the sounds group into separate perceptual streams and

Cross-octave masking of single tones and musical sequences: The effects of structure on auditory recognition

“…When transitions are reintroduced, the segregation effect is eliminated (Dorman et aI., 1975). Taken with the Bregman and Dannenbring (1973) finding, these results suggest that perceptual splitting on the basis of frequency ranges can be overcome by the presence of a higher level of organization, though it is not clear that this finding in turn supports the preattentivemechanism formulation.…”

“…First, Bregman and Dannenbring (1973) introduced frequency transitions between alternating high and low tones in an attempt to impose a higher order structure which would prevent stream segregation. In both a standard-comparison task similar to that employed by Bregman and Campbell (1971) and in direct judgments by observers of the number of streams present in a sequence, transitions between tones decreased the amount of perceptual splitting obtained.…”

Auditory streaming is cumulative.

“…A second may be the rule of continuity: If changes are continuous, then only one source exists. This rule has been shown to exist (Bregman & Dannenbring, 1973). Both the discontinuity and the dissimilarity of successive moments of sound can be viewed as evidence that there is more than one source involved in producing the acoustic input.…”

Pattern identification of pure tones and frequency glides by untrained listeners

“…Glissandi considerably degraded identification performance for all subjects. Bregman and Dannenbring (1973) also used glissandi, finding an improvement to connect tones; however, it is clear that the use of a glissando as an event, even when it connects events in frequency, does not necessarily (in our data, ever) facilitate sequential order judgments (cf. d' for Experiment 1 vs. for Experiment 2 in Table 1).…”

“…A few investigators have looked at the role of frequency glides (glissandi) in connecting tones within a sequence (see Bregman & Dannenbring, 1973). Others have reported on pitch perception of tone bursts in the presence of continuous vs. discontinuous glissandi (Nabelek, Nabelek, & Hirsh, 1973).…”