VCV Context Research Articles

Some characteristics of oral air flow for fricative consonants produced by hearing‐impaired speakers

The average volume velocities of oral air flow during production of fricative consonants by ten normal‐hearing, ten moderately to severely hearing‐impaired and ten profoundly‐deaf adult males were investigated. Air flow was measured during production of CV and VCV syllables consisting of the vowel /a/ and the consonants /z/, /s/, /v/, and /f/. All hearing‐impaired and deaf subjects had congenital hearing losses and were able to intelligibly produce the syllables. The results indicated that for all three groups of subjects, in both syllable environments, the voiceless fricatives were characterized by greater oral air flow than their voiced cognates. In addition, in both the CV and VCV contexts, the average individual flow rates associated with each of the four fricatives were similar for the normal‐hearing and hearing‐impaired groups. With respect to the deaf subjects, however, the average individual flow rates for each of the four fricatives were significantly greater in the CV context and significantly less in the VCV context, when compared with the normal‐hearing and hearing‐impaired subjects. [Work supported by HEW.]

Perceptual invariance for stop consonants in different positions.

The basis for the invariant perception of place of articulation in pre- and postvocalic stops was investigated using the selective adaptation paradigm. Experiments 1 and 2 considered the role of identical bursts, mirror-image formant transitions, and similar onset and offset spectra in the invariant perception of place of articulation in CV and VC stimuli, and Experiment 3 considered the importance of the second two cues in a VCV context. The results of these experiments suggest that, at the level of processing tapped by selective adaptation, neither identical bursts, mirror-image formant transitions, nor similar onset and offset spectra are the basis for the invariant perception of place of articulation in initial and final position. The vowel portion of an adapter was found to affect perception of the consonant portion of a stimulus, and the direction of this effect was predictable from the acoustic characteristics of the consonant and vowel. The implications of these findings for the nature of selective adaptation are discussed.

Lip and mandible coordination during the production of bilabial and labiodental consonants in English

The production of bilabial and labiodental consonants requires a major articulatory constriction in the most anterior part of the vocal tract. This constriction is formed by the movements of the lips and mandible. Experiments were conducted to examine lip and mandible movements during the production of /p, b, m, f, v, w/ in a VCV context (V = /a/). Reflectors (< 1.3 mm in diameter) were placed on the subject's lips and on rigid wires attached to a mandibular tooth and the head. Reflector displacements on the midsagittal plane together with voice spectra were digitized and recorded every 10 msec. The locations of the reflectors with respect to the maxillary incisors were analyzed after correcting for head movements. Inter- and intrasound production characteristics of these consonants will be discussed according to the displacement and velocity values of lip and mandibular movements. [Supported by NIR Grant NS-11852-01A from NINDCDS.]

Lip and jaw coordination during the production of /f, v/ in English

The major articulatory constriction for the fricative consonants /f, v/ in English is established by the contact of the maxillary incisors and the lower lip. The constriction is formed by the movements of the lower lip and the mandible. Experiments were conducted to examine lip and jaw movements during the production of /f, v/ in VCV Contexts (V = /i, ε, æ, ɑ, o, u/). Reflectors (<1.5 mm in diameter) were placed on the subject's lips and on rigid wires attached to the jaw and head. Reflector displacements on the midsagittal plane together with voice and upper-teeth-lower-lip contact information were digitized and recorded every 10 msec. The locations of the reflectors with respect to the maxillary incisors were analyzed after correcting for head movements. Preliminary analysis indicated differences in lip and jaw displacement as a function of (1) phonetic context and (2) speaking rate. Results will be contrasted with findings by other investigators for bilabial stops. [Supported by NIH Grant NS-11852-01A from NINDCDS.]

Speech rate influences on the perception of stop voicing

Measures from speakers of British English show that voice-onset times (VOT's) produced in prestressed, prevocalic stop-consonants decrease as speech rate increases. Complementary adjustments occur in perception: if the syllabic rate of a synthetic precursor phrase which introduces test syllables drawn from a CV VOT continuum is increased, phoneme boundaries shift to shorter VOT's. The perceptual effect (a) is dependent upon timing variations in at most the 750 msec of the precursor immediately preceding the test syllable; (b) is almost unaffected by a mismatch of vocal tract length between precursor and test syllable; and (c) is substantially diminished if the silent closure interval between precursor and test syllable is longer than about 100 msec. These results suggest that the effect is not subsumed by the perceptual extraction and application of a speaker-dependent, speech-rate parameter but depends upon immediate computations of timing relations over short stretches of perceptually continuous running speech. Further experimentation is required to specify how perceptual measures of the durations of the vowels, the closure interval and the VOT, in VCV contexts, interact and so to determine the status of these variables as cues and/or contexts for the perception of stop voicing in running speech. [Work supported by J.S.R.U. at The Queen's University of Belfast, U.K.]

Consonant Durations in a Cluster Environment

The durations of initial and final consonant clusters in monosyllabic words within a frame sentence were studied from spectrograms of reading by speakers. The durations of consonants within a cluster varied with the features of the consonant and its phonetic environment, such as voicing and point and manner of articulation. A durational model was proposed based on two mechanisms: an articulatory mechanism was responsible for effects involving motion of the tongue and lips during a cluster. Shortening of consonants in clusters was attributed to the shorter distances that the articulators travel in clusters. Lengthening of consonants before fricatives and aspiration duration effects were part of this articulatory mechanism. The other factor was a “learned” mechanism, related to the use of duration as an acoustic cue in consonant perception. Phonetically similar single consonants had substantial durational differences which could aid in distinguishing them. Phonological restrictions, which do not occur in VCV contexts, arise in clusters; and when adjacent consonants provided information about another consonant's features, durational differences were less. [This research supported by an NSF Fellowship.]

Effects of distance on the visual reception of speech.

Two talkers with normal hearing and speech presented with voice 240 common nouns (80 monosyllables, 80 trochees, 80 spondees) to six profoundly deaf children whose task was to lipread without acoustic cues at distances from 5-100 ft. Under bright, shadow-free illumination, lipreading performance diminished from 75% correct at 5 ft to 11% correct at 100 ft. Scores varied with distance similarly for both talkers. The stress patterns of the stimulus words influenced their intelligibility, with scores decreasing from spondees to trochees to monosyllables. In a supplementary study, one talker presented two tests of phoneme recognition to the same six deaf children whose task was to lipread from 5, 20, or 70 ft. Identification of consonants in VCV context depended on their place of articulation (front superior to back) and on the surrounding vowel (/a–a/ superior to /i–i/ or /u–u/). Vowel-identification scores were less dependent on distance than were consonant-identification scores. In general, tense (stressed) vowels were more easily identified in /b/-V-/b/ context than were lax (unstressed) vowels.