Limits on the limitations of context-conditioned effects in the perception of [b] and [w]

120

A series of studies was undertaken to examine how rate normalization in speech perception would be influenced by the similarity, duration, and phonotactics of phonemes that were adjacent or distal from the initial, target phoneme. The duration of the adjacent (following) phoneme always had an effect on perception ofthe initial target. Neither phonotactics nor acoustic similarity seemed to have any influence on this rate normalization effect. However, effects of the duration of the nonadjacent (distal) phoneme were only found when that phoneme was temporally close to the target. These results suggest that there is a temporal window over which rate normalization occurs. In most cases, only the adjacent phoneme or adjacent two phonemes will fall within this window and thus influence perception of a phoneme distinction.One of the fundamental issues in speech perception research involves the apparent lack of invariance between the acoustic signal and the listener's perception. Listeners somehow manage to perceive messages correctly, despite the variability in the acoustic signal caused by changes in speaking rate, talkers, and dialect. Researchers often have tried to examine each of these issues separately, in the hope that they would later be able to combine their findings into one theory.One of the sources of variability in the acoustic signal is the rate at which a person speaks. People do not talk at a constant rate, and certain phonemes change substantially in duration as speaking rate changes (Crystal & House, 1982, 1990Miller, Grosjean, & Lomanto, 1984; or see Miller, 1981, for a review of earlier work). In addition, talkers differ in their intrinsic rate ofspeech (see Crystal & House, 1988d), and some dialects either lengthen sounds or shorten them. The issue ofrate change is especially important because some phonemic contrasts are cued, in whole or in part, by their duration. For instance, the fbl-/wl manner contrast can be cued by differences in duration alone, with shorter initial transitions being heard as more "b-like" and longer transitions as more "w-like" (Liberman, Delattre, Gerstman, & Cooper, 1956;Miller & Liberman, 1979). However, when we listen to someone who talks very quickly, we still hear Iwl phonemes: they do not all sound like stops. Conversely, when we listen to someone who speaks very slowly, intended fb/s do not all sound like Iw/s. Miller and Baer (1983) analyzed the transition This research was supported by NIDCD Grant RO 1-DC00219 to SUNY at Buffalo and by a National Science Foundation Graduate Fellowship to the first author. Some of these data were previously presented at the 123rd meeting of the Acoustical Society of America, May 1992, in Salt Lake City, and at the 124th meeting of the Acoustical Society of America, October 1992, in New Orleans. Comments may be sent to either author at the Department of Psychology, Park Hall, SUNY at Buffalo, Buffalo, NY 14260 (e-mail: rochelle@art.fss.buffalo.edu).durations for Ibal and Iwal and found that for a given speaking rate, Iwl transition...

Section: -R -----------supporting

confidence: 79%

“…If our It/-I sl series were of lower quality than our ItJI-IJI series, this post hoc explanation would work. Although there are no direct data available on this proposal, the results of Shinn, Blumstein, and Jongman (1985) and Miller and Wayland (1993) are suggestive. Shinn et aI.…”

Section: Resultsmentioning

confidence: 86%

Perceptual normalization for speaking rate: Effects of temporal distance

Newman

Sawusch

1996

120

“…For example, Gordon et al (1993) showed that directing attention to a concurrent task altered the relative importance of different acoustic cues during speech perception. Similarly, Miller and Wayland (1993) showed that adding noise to the speech signal increased the importance of overall syllable duration in the perception offbi versus Iw/. Perhaps variation in speech tokens along a particular dimension within a block of trials works in a similar fashion by directing attention to that dimension, increasing its importance during speech perception.…”

Section: Discussionmentioning

confidence: 99%

The encoding of rate and talker information during phonetic perception

Green

Tomiak

Kuhl

1997

The acoustic structure of the speech signal is extremely variable due to a variety of contextual factors, including talker characteristics and speaking rate. To account for the listener's ability to adjust to this variability, speech researchers have posited the existence of talker and rate normalization processes. The current study examined how the perceptual system encoded information about talker and speaking rate during phonetic perception. Experiments 1-3 examined this question, using a speeded classification paradigm developed by Garner (1974). The results of these experiments indicated that decisions about phonemic identity were affected by both talker and rate information: irrelevant variation in either dimension interfered with phonemic classification, While rate classification was also affected by phoneme variation, talker classification was not. Experiment 4 examined the impact of talker and rate variation on the voicing boundary under different blocking conditions, The results indicated that talker characteristics influenced the voicing boundary when talker variation occurred within a block of trials only under certain conditions, Rate variation, however, influenced the voicing boundary regardless of whether or not there was rate variation within a block of trials. The findings from these experiments indicate that phoneme and rate information are encoded in an integral manner during speech perception, while talker characteristics are encoded separately.Research over the past 30 years has revealed numerous aspects of the acoustic signal that playa role in phonetic perception, Theories of speech perception have attempted toexplain how these acoustic characteristics are processed, integrated, and mapped onto the underlying phonetic representations, Such explanations have been hampered by the complex relationship between the characteristics of the signal and the underlying phonetic representations.

“…However, this issue has been extremely difficult to resolve because parallel results in two domains indicate only that a common mechanism of processing is possible (see also Fowler, 1990). Another issue has been the extent to which these effects occur in the perception of fluent natural speech and whether they are simply a result of using highly impoverished, reduced stimuli (see Miller & Wayland, 1993;Shinn, Blumstein, & Jongman, 1985). The relative automaticity of this effect and the locus in perceptual processing of normalization for the rate of events have also been addressed (see Lotto, Kluender, & Green, 1996;Miller & Dexter, 1988), as has the influence ofspeaking rate on the internal structure ofphonetic categories (Flege & Schmidt, 1995;Miller & Volaitis, 1989), and whether the effects are based on phonetic segment durations or syllable durations (see Miller & Liberman, 1979).…”

Section: -Accepted By Previous Editor Myron 1 Braunsteinmentioning

confidence: 99%

Perceptual normalization for speaking rate II: Effects of signal discontinuities

Sawusch

Newman

2000

In a series of experiments, we examined how rate normalization in speech perception is influenced by segments that occur after the target. Perception of the syllable-initial target was influenced by the durations of both the adjacent vowel and the segment after the vowel, even when the identity of the talker was changed during the syllable. These results, together with earlier findings of a temporal window that follows a target phoneme within which segment duration influences perception of the target, help to resolve apparently conflicting results that have been reported previously. Overall, the results fit within a theoretical framework in which the rate at which events take place is extracted early in processing, prior to segregating voices, and the use of this information is obligatory in subsequent processing.The process of perceiving speech involves achieving perceptual constancy in the face of substantial stimulus variation. In order to recognize a word, the listener must deal with variation between talkers and variation that occurs within the speech of a single talker. Between-talker differences include the length of the vocal tract, vocal fold mass and tension, articulatory habits, intrinsic speaking rate, and dialect. Within-talker effects include the emotional tone of the speech signal, the context in which segments occur, and the rate of speech.Our focus here is on how listeners achieve constancy in the face of variation in the rate of speech.