Linguopalatal Contact Research Articles

Influence of the palate shape on articulatory token-to-token variability

Articulatory token-to-token variability not only depends on linguistic aspects like the phoneme inventory of a given language but also on speaker specific morphological and motor constraints. As has been noted previously (Perkell (1997), Mooshammer et al. (2004)), speakers with coronally high "domeshaped" palates exhibit more articulatory variability than speakers with coronally low "flat" palates. One explanation for that is based on perception oriented control by the speaker. The influence of articulatory variation on the cross sectional area and consequently on the acoustics should be greater for flat palates than for domeshaped ones. This should force speakers with flat palates to place their tongue very precisely whereas speakers with domeshaped palates might tolerate a greater variability. A second explanation could be a greater amount of lateral linguo-palatal contact for flat palates holding the tongue in position. In this study both hypotheses were tested.
 
 In order to investigate the influence of the palate shape on the variability of the acoustic output a modelling study was carried out. Parallely, an EPG experiment was conducted in order to investigate the relationship between palate shape, articulatory variability and linguo-palatal contact.
 
 Results from the modelling study suggest that the acoustic variability resulting from a certain amount of articulatory variability is higher for flat palates than for domeshaped ones. Results from the EPG experiment with 20 speakers show that (1.) speakers with a flat palate exhibit a very low articulatory variability whereas speakers with a domeshaped palate vary, (2.) there is less articulatory variability if there is lots of linguo-palatal contact and (3.) there is no relationship between the amount of lateral linguo-palatal contact and palate shape. The results suggest that there is a relationship between token-to-token variability and palate shape, however, it is not that the two parameters correlate, but that speakers with a flat palate always have a low variability because of constraints of the variability range of the acoustic output whereas speakers with a domeshaped palate may choose the degree of variability. Since linguo-palatal contact and variability correlate it is assumed that linguo-palatal contact is a means for reducing the articulatory variability.

The effect of syllable position on consonant reduction (evidence from Catalan consonant clusters)

This paper is an electropalatographic and acoustic investigation of consonant reduction as a function of syllable position in several heterosyllabic consonant clusters of Catalan within the framework of the degree of articulatory constraint (DAC) model of coarticulation. Three contact indices, i.e., alveolar contact anteriority and centrality and dorsopalatal contact quotient, are used for the computation of the linguopalatal contact characteristics for alveolar, alveolopalatal and velar consonants, with care taken to differentiate contextual effects from effects associated with syllable position. Results show that relatively unconstrained stops, nasals and laterals are produced with less front lingual contact and less dorsopalatal contact in syllable final vs. syllable initial position while this is not so for highly constrained fricatives and rhotics. A trend for the palatal fricative vs. the alveolar fricative to exhibit a wider constriction syllable finally vs. syllable initially is also attributed to stricter demands on constriction formation for the latter fricative vs. the former. Overall, these findings are in agreement with the notion that articulatory reduction in syllable final position is conditioned by constraints on consonantal production.

発話時における舌-口蓋接触力の簡易計測法

This paper proposes a using probe for measuring of contact force between tongue and palatal, during speech. We developed a 0.03 mm-thick stainless steel tongue force probe with a 3x5 mm force sensor at the tip. Linguopalatal contact force was measured by inserting the probe into the oral cavity. Contact force was measured at the following three locations. Based on the coordinate and measurement obtained at the three points, the action point of tongue force was calculated by the weighted mean. Linguopalatal contact force was measured in four adult men and women without articulation disorder and in three adult men with articulation disorders. Results showed that the action point of tongue force in subjects with articulation disorders was further toward the pharynx than that in subjects without articulation disorders. Linguopalatal contact pressure was then measured again by asking the subjects with articulation disorders to wear a palatal augmentation prosthesis (PAP) to compensate for insufficient linguopalatal contact force. The action point of tongue force became better approximated to that of subjects without articulation disorders. Given these results, our simple method for measuring linguopalatal contact force using a tongue force probe appears to be a promising tool for speech therapists treating articulation disorders.

Combining MRI, EMA and EPG measurements in a three-dimensional tongue model

A three-dimensional (3D) tongue model has been developed using MR images of a reference subject producing 44 artificially sustained Swedish articulations. Based on the difference in tongue shape between the articulations and a reference, the six linear parameters jaw height, tongue body, tongue dorsum, tongue tip, tongue advance and tongue width were determined using an ordered linear factor analysis controlled by articulatory measures. The first five factors explained 88% of the tongue data variance in the midsagittal plane and 78% in the 3D analysis. The six-parameter model is able to reconstruct the modelled articulations with an overall mean reconstruction error of 0.13 cm, and it specifically handles lateral differences and asymmetries in tongue shape. In order to correct articulations that were hyperarticulated due to the artificial sustaining in the magnetic resonance imaging (MRI) acquisition, the parameter values in the tongue model were readjusted based on a comparison of virtual and natural linguopalatal contact patterns, collected with electropalatography (EPG). Electromagnetic articulography (EMA) data was collected to control the kinematics of the tongue model for vowel-fricative sequences and an algorithm to handle surface contacts has been implemented, preventing the tongue from protruding through the palate and teeth.

Articulatory and acoustic studies on domain-initial strengthening in Korean

This study examines the effect of prosodic position on segmental properties of Korean consonants /n, t, th, t*/ along the articulatory parameters peak linguopalatal contact and stop seal duration, and several acoustic parameters. These parameters were compared in initial position in different domains of the Korean prosodic hierarchy. The first result is that consonants initial in higher prosodic domains are articulatorily stronger than those in lower domains, in the sense of having more linguopalatal contact. Second, there is a strong correlation between linguopalatal contact and duration (both articulatory and acoustic), suggesting that “strengthening” and “lengthening” is a single effect in Korean. We interpret this relation as one of undershoot: in weaker positions, consonants are shorter and undershoot contact targets. The different consonant manners of Korean can be characterized as varying in both duration and contact in this way. Third, there is another, less consistent, kind of lengthening and strengthening specific to Korean, namely that tense and aspirated consonant oral articulations can be longer and stronger word-medially than word-initially. Fourth, the acoustic properties VOT, total voiceless interval, %voicing during closure, nasal energy minimum, and to a lesser extent stop burst energy and voicing into closure, were found to vary with prosodic position and, in some cases, to correlate with linguopalatal contact. They could thus potentially provide cues to listeners about prosodic structure.

Articulatory properties of initial segments in several prosodic constituents in French

This study reports on how what is usually called “segmental” articulation may be affected by prosodic structure. Articulatory properties of segments of various types are compared in initial position of four prosodic constituents in French: an Intonational Phrase, an Accentual Phrase, a Word and a Syllable. Modification of linguopalatal contact, nasal flow, acoustic measures of glottal articulation, as well as durational properties of segments are examined depending on these prosodic positions. Results show that the articulation of initial segments varies according to the prosodic level of the constituent. Initial segments in higher prosodic domains tend to have more linguopalatal contact, somewhat less nasal flow for nasals, and vowels tend to be more frequently glottalized than in initial position in lower domains. The magnitude and the realization of the articulatory modification observed in these positions is found to depend on speakers, articulators, and segment types. However, the regular trend observed suggests that these articulatory properties can reflect the prosodic encoding of constituents of various levels within utterances.

Post obstruent tensing in Korean: Its status and domain of application

The criteria that distinguish the phonological rules from the phonetic rules based on categoricality versus gradiency have drawn considerable attention (cf. Keating, 1990; Pierrehumbert, 1990). Korean Post Obstruent Tensing (POT) rule has been claimed, based on acoustic data, to be a phonological rule and that its domain of application is an accentual phrase (AP) (e.g., Jun, 1998). This paper questions the status of POT and its domain of application based on articulatory and acoustic data. By POT, a syllable initial lenis consonant (e.g., /t/, /s/) becomes tense (e.g., /t*/, /s*/, respectively) after an obstruent coda. It is known that lenis obstruents have a longer VOT, shorter closure durations, and shorter linguopalatal contact areas than tense obstruents. To investigate if POT is really a categorical process and if its application is definable in terms of an AP, acoustic and articulatory (i.e., EPG) data of derived and underlying tense obstruents were examined in four different prosodic positions: utterance-initial, intonational phrase-initial, AP-initial, AP-medial. Sentences containing a target sequence, /VpCV/, where C=/t/, /t*/, /s/, /s*/, were produced by two Korean speakers, at normal and fast speech rates. The results will shed light on the status of POT in the grammar of Korean.

Acoustic correlates of articulatory prosodic strengthening in Korean

Recent articulatory studies [e.g., Keating, Cho, Fougeron, and Hsu (1998), forthcoming] using electropalatography have shown that consonants are generally produced with greater linguopalatal contact in domain-initial positions. This effect, known as articulatory prosodic strengthening, is generally cumulative: the higher the prosodic position, the more linguopalatal contact. The goal of this paper is to test for acoustic correlates of any such articulatory variations in Korean consonants /n,t,th,t*/ in prosodic positions (Utterance-, IP-, AP-, Word- and Syllable-initial), so that eventually the perceptual significance of such correlates can be tested. Results show that the higher domain-initial positions are associated with longer VOTs; longer ‘‘total’’ voiceless duration in closure; lower rms burst energy in stops but with substantial inter-speaker/consonantal variations; lower % of voicing during closure; and lower acoustic energy for nasal /n/. In addition, vowels in domain-initial CV were not found to be necessarily longer in a higher position whereas vowels in domain-final positions were. Linear correlations between each of the acoustic parameters and the articulatory magnitude (linguopalatal contact) will also be discussed. All in all, this study shows that articulatory strengthening in Korean does produce reliable acoustic correlates, which mark off prosodic positions in the speech signal. [Work supported by NSF.]

Initial strengthening and coarticulatory resistance

In previous work, initial strengthening of lingual articulations has been demonstrated in four languages. One possible interpretation of initial strengthening is that it results from increased coarticulatory resistance: consonants in stronger positions resist the weakening that coarticulation would produce. To test this interpretation, a new study examined consonants in CVCs in which the vowel was varied. If initial strengthening is coarticulatory resistance, then there should be less effect of the vowel on the initial consonant than on the final consonant. Test consonants /t d n l/ and vowels /E a u/ were combined with the nontest consonant /b/ in 24 syllables like /tab/ and /bul/; five subjects produced nine repetitions of each in a frame sentence. Maximum linguopalatal contact, measured by electropalatography, was the measure of consonant strengthening and coarticulation. The result was the opposite from the prediction. Initial consonants showed more vowel-dependent variation than did final consonants (in accord with the traditional coarticulation literature). Yet the initial consonants did show more overall contact than final consonants. Thus initial strengthening cannot be attributed to coarticulatory resistance. Additional experiments, including one which looks at initial strengthening in phrase-initial positions, will be reported. [Work supported by NSF.]

Palatal augmentation prosthesis with alternative palatal vaults for speech and swallowing: A clinical report

Patients who have undergone extensive glossectomy for tongue cancer have various degrees of residual tongue volume and mobility, which results in a lack of linguopalatal contact that is essential for normal deglutition, mastication, and speech. Placement of a palatal augmentation prosthesis, which is fabricated so the palatal vault is lowered to provide increased linguopalatal contact, improves deglutition, and speech potential in patients with reduced tongue volume and movement. Defining the contour of the palatal vault requires a compromise between the needs for speech and swallowing,1 because the location and degree of linguopalatal contact differ between these two processes.

Word–initial versus word–final consonant articulation

The position of a consonant within its prosodic word is known to have an effect on the degree, or strength, of its articulatory stricture: in stronger prosodic positions, the active articulator may be higher, making the oral opening smaller. This study examines the robustness of this asymmetry in consonant articulation. Electropalatography was used with five speakers to determine linguo–palatal contact for several English consonants in word–initial versus word–final position. The various experiments manipulated such factors as identity of the consonant, the test word’s lexical stress, its position in its sentence, and phrasal accent in the sentence. Results show that: (1) noncontinuant consonants generally have more contact in word–initial than word–final position, but sibilant fricatives do not; (2) intonational–phrase–final position is a strong position, so that word–final consonants /t d n/, which are also sentence final often show little word–final weakening (/l/ is an exception for some speakers); and (3) in contrast to this positional effect, lexical stress and phrasal accent never strengthen word–final consonants in this way, nor do these prosodic factors consistently strengthen word–initial consonants. [Work supported by NSF.]

Articulatory strengthening at edges of prosodic domains.

In this paper it is shown that at the edges of prosodic domains, initial consonant and final vowels have more extreme (less reduced) lingual articulations, which are called articulatory strengthening. Linguopalatal contact for consonants and vowels in different prosodic positions was compared, using reiterant-speech versions of sentences with a variety of phrasings read by three speakers of American English. Four prosodic domains were considered: the phonological word, the phonological (or intermediate) phrase, the intonational phrase, and the utterance. Domain-initial consonants show more linguopalatal contact than domain-medial or domain-final consonants, at three prosodic levels. Most vowels, on the other hand, show less linguopalatal contact in domain-final syllables compared to domain-initial and domain-medial. As a result, the articulatory difference between segments is greater around a prosodic boundary, increasing the articulatory contrast between consonant and vowels, and prosodic domains are marked at both edges. Furthermore, the consonant initial strengthening is generally cumulative, i.e., the higher the prosodic domain, the more linguopalatal contact the consonant has. However, speakers differed in how many and which levels were distinguished in this way. It is suggested that this initial strengthening could provide an alternative account for previously observed supralaryngeal declination of consonants. Acoustic duration of the consonants is also affected by prosodic position, and this lengthening is cumulative like linguopalatal contact, but the two measures are only weakly correlated.

Velic and lingual articulations are affected by prosodic position for consonants but not vowels in French

This study investigates the effect of position-in-prosodic-domain on the velic and lingual articulation of French consonants and vowels. The segments were placed in five different prosodic positions: Utterance-initial, intonational phrase-initial, accentual phrase-initial, word-initial, and syllable-initial. Nasal airflow (considered as an indirect measurement of velum articulation) was recorded for [n] and the open nasal vowel [■] for four French subjects. Using electropalatography, linguopalatal contact was recorded for the dental consonants [n] and [t] and for the closed vowel [i] for two French subjects. Results show that consonants that are initial in a higher prosodic domain have more linguopalatal contact and less nasal flow. Moreover, more positions are distinguished by variation in linguopalatal contact than in nasal airflow. Results for vowels show that prosodic positions are distinguished by nasal airflow for only one speaker, and by linguopalatal contact for none of the speakers. Thus position-in-prosodic-domain can affect the articulation of two remote articulators but, at least for the articulators studied, the effect is restricted to consonant articulation. [Work supported by NSF.]

Articulatory characteristics of French consonants are maintained after the loss of schwa

The optional loss of schwa in French generates consonant clusters. Thus de rôle [d■rol] can be produced as d’role [drol] and is thought to become homophonous with drôle [drol]. This study compared articulatory and acoustic properties of [d] in these sequences in order to determine whether [d] maintains, after the loss of schwa, certain characteristics of the isolation form de. The sequences were inserted in a carrier sentence and repeated 20 times by three French speakers. Consonants were compared in terms of amount and location of linguopalatal contact (measured with EPG), their acoustic duration, and frequency of lenition (absence of closure). Preliminary results for one subject show that despite the complete disappearance of schwa, the [d] ind ’rôle has some of the same characteristics as the one in de rôle as opposed to drôle: longer duration, greater and more anterior linguopalatal contact, less lenition. These results suggest that the loss of schwa does not lead to resyllabification of [d] with either the preceding or following syllable, but rather that the consonant maintains the characteristic properties of the citation form. The significance of this result is that lexical distinctions are maintained in production, despite the apparent phonological neutralization induced by schwa loss.

Speech function following maxillectomy reconstructed by rectus abdominis myocutaneous flap

Post-surgical maxillary defects have recently been reconstructed by microvascularized free flaps. However, few reports have evaluated the resulting speech function. This study compared the speech intelligibility of four maxillectomy patients who underwent reconstruction by rectus abdominis myocutaneous flaps (RAMCF) with that of four non-reconstructed patients who were treated with split-skin grafts and prostheses, to explore ways of achieving better speech function. Speech function was assessed by a Japanese language speech intelligibility test. Intelligibility scores ranged from 57.3% to 75.8% (mean, 70.4%) in the non-reconstructed group and from 66.2% to 77.2% (mean, 71.0%) in the reconstructed group. An analysis of articulatory manners and sites revealed that speech disorders resulted mainly from poor oronasal separation in the non-reconstructed group and from incorrect linguopalatal contact in the reconstructed group, especially for linguodentoalveolar and linguovelar sounds. Therefore, for higher speech function in the reconstructed group, dentoalveolar and palatal contours of the maxilla must be restored as closely as possible. This must also be done in patients whose maxillae are reconstructed by other types of microvascularized myocutaneous or cutaneous flaps that have similar postoperative palatal contours.

Demarcating prosodic groups with articulation

It is hypothesized that phrasal position affects articulation, and that what looks like overall declination of articulatory displacement could arise from local enhancements or reductions at particular phrasal positions. To test this hypothesis, linguopalatal contact was measured for both the consonant /n/ and the vowel /o/ in reiterant speech. Utterances were based on arithmetic statements like ‘‘(1+1)×(1+1)’’ [reiterant ‘‘(no no no) no (no no no)’’], where stress and phrasing were varied by choice of numerals and location of parentheses. For the one speaker analyzed, there was no overall downtrend in contact of /n/ through any sentence type when all syllables—stressed, word-initial, or phrase-initial—were compared. Instead, word-, phrase-, and sentence-initial /n/’s have cumulatively more contact than medial and final ones. It is proposed that greater initial contact contributes to marking prosodic boundaries by enhancing the consonant–vowel contrast. Also enhancing the CV contrast is the more open position for phrase-final /o/’s. As a result, final edges of domains are marked by a greater articulatory distance from final /n/ to /o/, and initial edges of domains are marked by a greater articulatory distance from final /o/ to initial /n/.

EPG bidimensional data reduction.

A new method of electropalatographic (EPG) data reduction is proposed. It uses the so-called discrete cosine transform for representing an EPG pattern as a weighted sum of elementary 'pictures'. It is shown that several of these pictures can be considered as being articulatorily relevant. The respective contributions of these pictures to the spatial arrangement of the linguopalatal contacts are given by transform coefficients which are used here as a set of new EPG indices: the scaled sum of contacts index (SSU), the left-right asymmetry index (LRA), the alveolar-palatal index (APA) and the lateral-median index (LME). It is shown that the information extracted from an EPG pattern by means of these indices is maximised. Because of its robustness, this method could be usefully employed in studies on articulatory disorders.

Electropalatographic data collected with and without a face mask.

This study investigates the extent to which the use of a face mask conveys linguopalatal contact changes during speech production. Electropalatographic data from five Catalan speakers were collected for different consonants, i.e., the alveolar stop [n], the alveolopalatal stop [n] and the palatal approximant [j], in the sequences [iCi] and [aCe]. Results for [n] indicate more closure retraction in the mask versus nonmask condition occurring presumably when the mask is pressed forcefully against the face in front of the mouth. The use of the mask for [n] and [j] causes an increase in dorsopalatal contact, which reflects most likely a strategy of articulatory and/or perceptual compensation.

The contact index method of electropalatographic data reduction

This paper presents a new method of electropalatographic data reduction, namely, the contact index method. It provides accurate information about the distribution and size of linguopalatal contact based on values for an anteriority index, a posteriority index and a centrality index. These values are calculated using coefficients specific to each row of electrodes along the sagittal dimension and to each column of electrodes along the coronal dimension. The contact index method is applied to the analysis of two research topics: V-to-C coarticulation effects at the palatal zone for consonants differing in place and manner of articulation characteristics; and intraconsonantal variability across repetitions of a given VCV sequence. Results are evaluated in the light of the theory of speech production.

Cross-sectional tongue shape and linguopalatal contact patterns in [s], [∫], [f], and [1

The present study examined cross-sectional tongue shape and linguopalatal contact during [s], [∫], [1], [ε], [c], [o] and [a] in CVC utterances. Three cross-sectional scans of the tongue, anterior, dorsal and posterior, were made using ultrasound imaging. Linguopalatal contact patterns were determined from electropalatography data. Results indicated that cross-sectional tongue shape is very different among consonants, and at different anterior-to-posterior locations, indicating that the vocal tract is neither circular in shape, nor uniform along its length. These results are due to the anisotropic nature of the tongue’s musculature. In addition, tongue surface shapes, and thus vocal tract shapes, were affected by the bracing of the tongue against the palate (during consonants). Cross-sectional tongue shapes varied due to the location of the contact and the speculated amount of force used in the contact.