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Biomedical subjects

S G Fletcher

Publications and source records attributed to S G Fletcher.

14 recordsLinked to original sources
PubMed1992

Esophageal speaker articulation of /s,z/: a dynamic palatometric assessment.

Esophageal talker linguapalatal contact patterns and durations during /s/ and /z/ productions were examined using dynamic palatometry instrumentation. It was found that sibilant groove narrowing is a physiologic compensation for a reduced air supply in esophageal speech. The place of esophageal /s, z/ articulation was on the anterior portion of the alveolar ridge as seen in normal speakers. Average medial groove width for esophageal /s/ was narrower than the 5-7-mm groove characteristic of normal speakers. Groove widths averaged 3 mm for /s/ and 4 mm for /z/. Systematic changes in groove widths across speech sounds, syllable position, and vowel context were also observed. Use of a narrower lingual groove was interpreted as a significant articulatory maneuver to meter out a limited intraoral air supply and effect more normal fricative durations.

Articulation Disorders↗
PubMed1991

Teaching consonants to profoundly hearing-impaired speakers using palatometry.

Five profoundly hearing-impaired children were taught the consonants /t,d,k,g,s,z integral of/ using palatometry. Changes in linguapalatal contact patterns and listener perceptions showed significant improvement in the place and manner of consonants produced by all subjects. Velar stops were as easily and accurately learned as alveolar stops. Distinctive sibilants were also found by the end of training. Sounds not previously present in a subject's phonetic repetoire were learned more accurately than those present but inaccurate prior to therapy. Voicing errors persisted. Two of the subjects showed evidence of newly established, unsolicited coarticulated movements. The results indicated that visual articulatory modeling and feedback of linguapalatal contact patterns is an effective means of teaching consonants and improving speech intelligibility.

Adolescent↗
PubMed1991

Teaching vowels to profoundly hearing-impaired speakers using glossometry.

Glossometry was used to teach the four point vowels (/i,ae,u,a/) to 6 profoundly hearing-impaired children. Prior to treatment, all subjects evidenced centralized tongue positions during vowel productions. After 15 to 20 fifty-minute training sessions over 3- to 4-week time periods, all subjects showed greater diversification of tongue postures for the vowels, especially in tongue height. Listener identifications were generally better after therapy. The training results suggested that visually presented models and feedback of tongue positions can facilitate more appropriate tongue postures and improve vowel intelligibility by hearing-impaired speakers.

Adolescent↗
PubMed1991

[s] and [sh] as a function of linguapalatal contact place and sibilant groove width.

Sibilant groove place and width were initially examined during [s] [s] in isolation and in CV and VC syllables. The [s] was found to be produced through a 6- to 8-mm-wide groove near the front of the alveolar ridge by one talker and near the back of the ridge by the other. [s] was produced through a 10- to 12-mm groove behind the posterior border of the alveolar ridge by both. In the second experiment three subjects used visual articulatory feedback to vary sibilant groove width and place systematically. One subject was able to do this with comparatively few retrials; one had difficulty with certain targeted grooves; one had difficulty with many targeted grooves. The noises generated were replayed to 14 listeners who labeled them as "s," "probably s," "probably sh," or "sh." They usually heard the sound as [s] when the grooves were narrow and near the front of the alveolar process, [s] when the groove was wider and behind the alveolar process. Noise through grooves that matched natural speech places and widths usually produced higher listener recognition scores. Exceptions were found when the subjects had unusual difficulty in achieving stipulated groove widths and places.

Adult↗
PubMed1989

Palatometric specification of stop, affricate, and sibilant sounds.

This investigation used palatometry to study stops, sibilants, and affricates in CV syllables (C = t,d,k,g,tf,d3; V = i,a) spoken by nine normal 6- to 14-year-old children. The measures focused on place, manner, timing, and area of linguapalatal contact. Similarities and differences between the sound classes, actions across segments of the articulatory gestures, and age effects were identified and described. The affricates were observed to have stop and sibilant portions demarcated by a partial plateau in the linguapalatal contact releasing gesture. The sibilant portion was formed in the same place and with the same groove dimensions as /f,3/. The older subjects reached initial articulatory positions faster, produced the consonant sounds more quickly, generated vowels with shorter durations, and articulated more posteriorly than did younger ones.

Adolescent↗
PubMed1988

Speech production following partial glossectomy.

Changes in the dimensions and patterns of articulation used by three speakers to compensate for different amounts of tongue tissue excised during partial glossectomy were investigated. Place of articulation was shifted to parts of the vocal tract congruent with the speakers' surgically altered lingual morphology. Certain metrical properties of the articulatory gestures, such as width of the sibilant groove, were maintained. Intelligibility data indicated that perceptually acceptable substitute sounds could be produced by such transposed gestures.

Adult↗
PubMed1988

Compensating for a bite block in /s/ and /t/ production: palatographic, acoustic, and perceptual data.

Electropalatography was used to monitor linguapalatal contact patterns in /s/ and /t/. Talkers often compensated incompletely for a bite block, both immediately after its insertion (sample B1) and after 10 min of practice (sample B2). Significant differences in the number of sensors contacted were noted between normal and bite-block samples for both /s/ and /t/. Differences in length of constriction in /t/, and the A-P location and width of the groove in /s/ were also noted. The two native English subjects compensated better than three Arabic subjects, perhaps because English /s/ and /t/ are formed more posteriorily and with a smaller contact area than their Arabic counterparts. A significant correlation existed between the area and A-P location of linguapalatal contact. All five subjects formed a groove for /s/ in sample B2, but two often did not produce /t/ with complete constriction. This suggests a groove is critical for /s/, but complete constriction is not critical for /t/. The contact patterns in sample B2 more closely resembled normal speech than those in sample B1 in some instances, while in other instances the reverse was true. The conclusion that subjects sometimes overcompensated in sample B2 was supported by the results of detailed acoustic and perceptual analyses for one subject. Taken together, the results suggest that compensation for a bite block is not instantaneous, and that specific parameter values may be encoded in central phonetic representations.

Adult↗
PubMed1976

Nasalance in utterances of hearing-impaired speakers.

Instrumental comparisons of sound from the nose and mouth expressed in percent nasalance, articulation errors, and speech rate are used in this study to contrast utterances of 50 speakers with severe hearing impairment and 64 with normal hearing. Results of the study revealed that 54% of the hearing-impaired subjects had nasalance ratio scores greater than two standard deviations above the mean of the group with normal auditory acuity. No general relationship was found between the number or type of articulation errors and the nasalance scores. Rate of speaking was significantly related to the nasalance scores of the normal group but not those of the hearing-impaired group. Tonagrams displaying the variations in nasalance revealed small, 1 to 50% spike-shaped fluctuations in the displays of the utterances from both groups. Additional prolonged bursts of nasalance in excess of a 30% change in the ratio between the nasal and oral signal were common in the displays from the hearing-impaired group did not in those of the group with normal acuity. Possible sources and perceptual effects of these phenomena are discussed.

Adolescent↗
PubMed1976

"Nasalance" vs. listner judgements of nasality.

In this article, judgements of nasality from sound field recorded utterances of 23 children with repaired palatal clefts are compared with "nasalance" values derived from TONAR II analyses of parallel sound separated recordings. For the nasality judgements, the sound field recordings were presented in forward reproduced mode to 20 "naive" listeners and in backward reproduced mode to 10 naive listeners. A four-level task progression was followed in each mode of presentation: sorting the responses by "normal" or "abnormal" nasality, ranking them by severity of nasality, classifying them within five degrees of nasality, and, finally, assigning a discrete score to the magnitude of nasality perceived in each recording. Scores from the individual judges were highly variable, especially in the first listening task. They were consitently more variable when nasality was judged from backward reproduced recordings. As the listeners gained experience and as the listening tasks demanded more precision in nasality judgements, variability was reduced. Correlations computed between the nasality ratings and nasalance measurements increased and variability decreased. Highest agreement between physical and perceptual measurements was found when variability among the judges was reduced by pooling the scores and comparing the mean scores of nasality with the nasalance scores. Using this procedure, a correlation of .91 was obtained between listener judgemental scores of forward reproduced speech and nasalance scores. Under these conditions, the instrumental score could apparently account for over 80 per cent of the variability in the listener judgements of nasality. From the findings of this study, it was concluded that listeners without prior training are capable of judging nasality reliably and that nasalance scores provide a valid correlate of perceived nasality. The use of backward reprodeced recordings was questioned as a means of assessing nasality.

Acoustics↗
PubMed1975

Dynamic palatometry.

A computer-based instrumental system is described for continuous palatometry. Thin pseudopalatal plates (approximately 0.2 mm) with embedded electrodes are used to detect linguapalatal contact during speech articulation. Geometric configurations of such contacts are then derived and displayed to reveal articulatory characteristics.

Computers↗