Palatographic Data Research Articles

Phonetic Structures of Scottish Gaelic

Scottish Gaelic is an endangered language with very few fluent speakers under 60. Recordings were collected in the neighbourhood of Greater Bernera, Lewis, from 11 native speakers. Aerodynamic and palatographic data were collected from one 70-year-old male speaker. Palatographic data made in 1955 by Frederick Macaulay, a Gaelic speaker from South Uist, provided additional information. Analysis showed that all the stops were voiceless unaspirated or aspirated, with the aspirated stops being preaspirated intervocalically. Spectra of various consonants were also determined. Vowel analyses showed the nature of the 7 long and short vowels. Special attention was paid to the back unrounded vowels. Problems of syllabicity were examined and shown to affect pitch contours.

Three-dimensional visualization of electropalatography

Electropalatography (EPG) is a widely used noninvasive technique for monitoring dynamic tongue-palate contact patterns in speech research and speech clinics. However, the conventional two-dimensional (2D) visualization system is incapable of informing individual characteristics of three-dimensional (3-D) palatal shape or the relationship between electrode positions and anatomical landmarks (e.g., teeth). This paper reports a method for visualizing tongue-palate contact patterns on the 3-D palatal shape display. A convex palatal shape model was formed by silicone impression material from an individual dental cast, and electrode positions on the individual-specific artificial palate (RION SP-01, 63 electrodes) were marked on the surface of the convex model. The 3-D geometry and the surface texture information of the convex model were extracted by a laser beam scanner (Cyberware 4020). Then, palatographic data were collected through the EPG system (RION DP-20) and the tongue-palate contact patterns were mapped on the 3-D graphical display of the palate. Preliminary observation of Japanese fricatives revealed vertical differences in constriction between [s] and [■]. Its application to speech production research and speech training will be discussed.

Rounding and palatalization convergence in Twi.

This paper reports an acoustic and articulatory study of labio‐palatalization in Twi Akan (West African). Labio‐palatalization is rare cross‐linguistically, as would be predicted from theories of vowel dispersion, since palatalization and labialization have opposite effects on second formant frequency. Labio‐palatalization in Twi, however, is the ongoing result of a convergence of contrastive consonant rounding and vowel‐induced palatalization which have been functionally combined in certain segments. Preliminary palatographic data indicate that rounded coronal consonants have more posterior coronal constrictions. Present acoustic analyses show rounded consonants to be marked by a lowering of F3. Combining coronal retraction and rounding, thus has two effects. (1) It produces a stable region of low F3, as indicated by nomograms in Wood (1986). (2) It increases front cavity length, resulting in a lower and more compact spectrum of consonantal frication noise. Thus 1) examining the role of uncommon contrast...

Articulatory and acoustic differences between palatal and velar stops

Many experimental studies have shown that velar consonants have a more forward place of articulation in front vowel contexts than in back vowel contexts. On some accounts, such velar fronting is basically the same process as the secondary articulation of palatalization, and furthermore, both “fronted” and “palatalized” velars are equated with the “palatal” cononants of other languages. In this study, velar stops (in English, Russian, Czech, Hungarian) are compared with palatal stops (in Czech, Hungarian) and with palatalized velar stops (in Russian) in different vowel contexts. X-ray and palatographic data from the literature show that palatalized velars are very much like velars in high front vowel context, but that both of these are very different from palatals. Acoustic analysis comparing spectra of consonant release and the following vowel agrees with the articulatory data. It also makes clear that languages with palatals also have fronted velars, differing in the distribution of energy across frequencies. These results indicate that palatalization of velars is phonetically equivalent to fronting, but that neither fronted nor palatalized velars are like the palatal consonants.

The articulatory characteristics of palatal consonants

This paper proposes a revision of the phonetic characterization of palatal consonants in light of X-ray, linguographic and palatographic data in the literature, and of some electropalatographic data collected by myself. These data show that the production of palatal consonants may involve a higher degree of articulatory precision than previously assumed, and that a classification that takes the prepalatal, mediopalatal and postpalatal zones into account is needed. It is suggested that four classes of palatal consonants ought to be distinguished: namely, alveolopalatals, front palatals, mid palatals and back palatals. Contrary to previous proposals in the phonological literature, the articulatory data reported here do not support the claim that palatal consonants are complex segments (i.e., involving two articulators).

Analysis of tongue motion for the dental consonants based on the high-speed palatographic data

Using a new high-speed palatograph system, tongue motions for dental consonants were recorded at a rate of 250 frames per second, and contact patterns of different consonants were compared using the gross features of the contact area (front-back position and high-low position). Each of five male subjects uttered 30 nonsense English syllables. /hə'CV/ (C = /t,d,n,s,z,r/, V = /a,i,u,e,o/). Then the front-back position of the contact area is represented by the position of the center of gravity of the contact area. Information on the vertical position of the tongue was expressed by the total number of contact points between the tongue and the palate. Representation of the contact pattern in the two-dimensional space of these parameters shows the characteristic feature for each utterance. A distinctive feature among the plosives /t,d,n/ is that the tongue position is more frontal and/or higher for /t/ than for the other two plosives /d,n/. As for the fricatives /s/ and /z/, the tongue position for the latter is usually more frontal than for the former. [Work supported by MESC of Japan.]

Observations on the release of /t/

Palatographic data were examined for the release of prevocalic /t/ in both aspirated and unaspirated contexts. Thirty-two tongue contact points in the alveolar region were sampled every 2 ms. Although a plosive burst is a sudden acoustical event, the dynamic tongue release gesture is more gradual. The burst is associated with the sudden opening of a narrow central channel between the tongue and palate. The tongue then continues to pull away from contact centrally, with the final contacts remaining laterally even after voicing for the following vowel has commenced. At some point during the release of /t/, the tongue contact pattern passes through a configuration virtually identical to that for the greatest constriction of /s/. This implies that a brief period of frication generated at the point of release may follow the burst. The sequence of acoustical events at the release of aspirated /t/ would be: burst-frication-aspiration. Tongue releases in a unaspirated context (/st__/) were also examined. The palatographic pattern of tongue release was no different for the unaspirated context, although the timing of its initiation was later relative to the beginning of the following vowel. [Work supported by NIDR.]

Speech adaptation to dental prostheses: The former lisper

Six of 13 former lispers studied reported unusual difficulty in speech adaptation to a dental prosthesis. Palatographic data showed that former lispers tended to make more frequent use of A-P shifts in tongue-palate placement as a compensatory strategy than did normal subjects. Tongue advancement was a common pattern. The nonadaptors showed the highest incidence of A-P tongue contact shifts as a compensatory strategy. Their use of this strategy was the most consistent, and they were more likely to retain the same articulatory speech patterns that were tried initially. Tongue groove width data for sibilants of nonadaptors in the familiar condition showed a substantial incidence of further groove narrowing, a pattern normally seen only when a prosthesis is unfamiliar to the subject. In data on jaw position, nonadapting subjects had either not changed jaw position or adopted a closer jaw position by the end of 2 weeks. In both palatographic and jaw position data, it was possible to distinguish the adapting and nonadapting groups.

Persistence of learned motor patterns in speech

It has been noted that “spontaneous” compensations are made during speech for articulatory constraints such as clenching of the jaw. On the other hand, at least several days are required for speech adaptation to a dental prosthesis. A recording of speech and physiological data on jaw activity and tongue contacts was made at the time of initial insertion of an experimental dental prosthesis. Subjects wore the prothesis for two weeks of adaptation, after which a second recording was made, and then waited at least 1 month without experience in speaking with it. A follow‐up recording was then made with the same protocol as when the prosthesis was first inserted. Speech sounded much less disturbed by the insertion of the prothesis after a lapse of a month than it had at initial insertion—knowledge of the compensatory adjustments required had evidently been retained over that period of time. Palatographic data showed a rapid progression toward the compensatory pattern within a few repetitions of the speech sample. [Work supported by NIH.]