A series of experiments was conducted to determine (1) the accuracy with which vowel segment durations in spoken sentences can be represented in auditory sensory storage and (2) the extent to which phoneme boundaries in the identification of phonetalc vowel length in Dutch are affected by syntactic and/or auditory-phonetic context. In a preliminary production test it was found that durations of both long and short Dutch vowel phoneroes in monosyllabic words embedded in sentences are systematically .. affected by word positions in the sentences. In an initial perceptual experiment, phoneme boundaries and slopes of identification curves were measured for 12 listeners in five different test utterances in a binary forced choice identification test. Perceptual accuracy of vowel duration perception as determined from the slopes of the identification curves corresponds on the average to a just-noticeable difference (JND) of about 5 ms with a test segment duration of about 90 ms. Phoneme boundary values are systematically affected by context in ways predictable from syntactic structure and the auditory-phonetic environment.In a second perceptual experiment it is shown that a major effect on phoneme boundary can be brought about by perceived properties of the test utterance following the monosyllable containing the test segment. In a third perceptual experiment it is shown that the difference between phoneme boundaries in utterance final syllable and in embedded syllable is related to the presence or absence of a perceived speech pause following that syllable. The results of these experiments are interpreted in terms of a simple decision model with a noisy auditory representation of embedded vowel duration, lasting a few hundredths of milliseconds, and a noiseless internal criterion for vowel length identification which is systematically affected by the auditory-phonetic environment.

No abstract

Knowing the position of lexical stress in a polysyllabic word may considerably limit the number of lexically possible responses. Thus perceptual cues may contribute to a higher probability of correct recognition and faster recognition of words in the perception of speech of less than optimal quality. Probability correct was assessed for 30 three-syllable Dutch words, synthesized from diphones. All words were of CVCVCVC phonemic structure, containing no consonant clusters. Ten words each had initial, medial, or final lexical stress. Stress position was either not cued at all, cued by durational cues only, cued by a conspicious pitch movement, or cued by both durational and pitch cues. Each word in each condition was responded to by five listeners. Scores correct, averaged over stress position, were 66% with no stress cues, 74% with durational cues, 81% with pitch cues, and 81% with durational and pitch cues combined. The contribution of stress cues was strongest for words with initial stress (from 54%–76%), and minimal for words with final stress (from 80%–88%). To investigate the effect of stress cues on the rapidity with which listeners tune in on the correct response, a gating-paradigm-type of experiment was performed on the same material. However, in this task errors against stress position were much more frequent, and positive effects of stress position were small.