Timing of pitch movements and perceived vowel duration

The hypothesis was tested that the timing of accent-lending pitch movements influences the perceived duration of a vowel. Dutch subjects were asked to adjust the physical duration of a vowel so as to fit into the temporal structure of a sentence. The vowel occurred in a monosyllabic word embedded in a carrier sentence. Three pitch movements on the vowel were used, a rise, a rise-fall, and a fall. Two opposite trends were found: the earlier the fall, the longer the duration of the target vowel was adjusted, the earlier the rise or rise-fall, the shorter its duration was adjusted. Control experiments indicated that the results should be interpreted in terms of a trade-off between the effects on prominence of timing of pitch movements and physical segment duration. It is concluded that late timing of pitch movements enhances the perceived vowel duration, but that this effect depends on the kind of pitch movement: the effect is cancelled in the case of late rises and rise-falls, whereas it is enhanced in the case of late falls by virtue of the enhancing effect on prominence of the accented syllable

Constraints on theories of human vs. machine recognition of speech

The central issues in the study of speech recognition by human listeners (HSR) and of automatic speech recognition (ASR) are clearly comparable; nevertheless the research communities that concern themselves with ASR and HSR are largely distinct. This paper compares the research objectives of the two fields, and attempts to draw informative lessons from one to the other

Can lexical knowledge modulate prelexical representations over time?

The results of a study on perceptual learning are reported. Dutch subjects made lexical decisions on a list of words and nonwords. Embedded in the list were either [f]- or [s]-final words in which the final fricative had been replaced by an ambiguous sound, midway between [f] and [s]. One group of listeners heard ambiguous [f]-final Dutch words like [kara?] (based on karaf, carafe) and unambiguous [s]-final words (e.g., karkas, carcase). A second group heard the reverse (e.g., ambiguous [karka?] and unambiguous karaf). After this training phase, listeners labelled ambiguous fricatives on an [f]-[s] continuum. The subjects who had heard [?] in [f]-final words categorised these fricatives as [f] reliably more often than those who had heard [?] in [s]-final words. These results suggest that speech recognition is dynamic: the system adjusts to the constraints of each particular listening situation. The lexicon can provide this adjustment process with a training signal