Australian adults' production of /n/: an EPG investigation

EPG research and therapy: further developments

Electropalatography (EPG) has been used in the past 50 years for studying the patterns of contact between the tongue and the palate during speech production in typical speakers and those with speech disorders due to different causes. At the 7th EPG Symposium in Japan that was held online on 24 January 2021 (see: https://epg-research.sakura.ne.jp/), a panel of invited experts discussed their views regarding further developments and application of the technique. This paper provides a summary of this discussion. EPG offers information on articulation which cannot be replaced by other instrumental measures of speech. Identified areas for further hardware development are thinner EPG plates, better dental and palatal coverage, wireless connectivity, and sensors that provide additional articulatory information (e.g. tongue pressure, tongue-palate distance). EPG can serve as a resource for teaching speech disorders and phonetics. Furthermore, EPG therapy can be combined with telepractice in the speech therapy of clients with speech disorders.

An ultrasound and formant study of manner contrasts at four coronal places of articulation

This study examines consonant manner of articulation at four coronal places of articulation, using ultrasound and formant analyses of the Australian language Arrernte. Stop, nasal, and lateral articulations are examined at the dental, alveolar, retroflex, and alveo-palatal places of articulation: /t̪ n̪ l̪ / vs /t n l/ vs /ʈɳɭ/ vs /c ɲ ʎ/. Ultrasound data clearly show a more retracted tongue root for the lateral, and a more advanced tongue root for the nasal, as compared to the stop. However, the magnitude of the differences is much greater for the stop∼lateral contrast than for the stop∼nasal contrast. Acoustic results show clear effects on F1 in the adjacent vowels, in particular the preceding vowel, with F1 lower adjacent to nasals and higher adjacent to laterals, as compared to stops. Correlations between the articulatory and acoustic data are particularly strong for this formant. However, the retroflex place of articulation shows effects according to manner for higher formants as well, suggesting that a better understanding of retroflex acoustics for different manners of articulation is required. The study also suggests that articulatory symmetry and gestural economy are affected by the size of the phonemic inventory.

Manner and place differences in Kannada coronal consonants: Articulatory and acoustic results

This study investigated articulatory differences in the realization of Kannada coronal consonants of the same place but different manner of articulation. This was done by examining tongue positions and acoustic formant transitions for dentals and retroflexes of three manners of articulation: stops, nasals, and laterals. Ultrasound imaging data collected from ten speakers of the language revealed that the tongue body/root was more forward for the nasal manner of articulation compared to stop and lateral consonants of the same place of articulation. The dental nasal and lateral were also produced with a higher front part of the tongue compared to the dental stop. As a result, the place contrast was greater in magnitude for the stops (being the prototypical dental vs retroflex) than for the nasals and laterals (being apparently alveolar vs retroflex). Acoustic formant transition differences were found to reflect some of the articulatory differences, while also providing evidence for the more dynamic articulation of nasal and lateral retroflexes. Overall, the results of the study shed light on factors underlying manner requirements (aerodynamic or physiological) and how the factors interact with principles of gestural economy/symmetry, providing an empirical baseline for further cross-language investigations and articulation-to-acoustics modeling.

Production of two Nasal Sounds by Speakers with Cleft Palate

Many speakers with cleft palate develop atypical consonant productions, especially for pressure consonants such as plosives, fricatives, and affricates. The present study investigated the nature of nasal sound errors. The participants were eight female and three male speakers with cleft palate between the ages of 6 to 20. Speakers were audio-recorded, and midsagittal tongue movement was captured with ultrasound. The speakers repeated vowel-consonant-vowel with the vowels /α/, /i/, and /u/ and the alveolar and velar nasal consonants /n/ and /η/. The productions were reviewed by three listeners. The participants showed a variety of different placement errors and insertions of plosives, as well as liquid productions. There was considerable error variability between and within speakers, often related to the different vowel contexts. Three speakers co-produced click sounds. The study demonstrated the wide variety of sound errors that some speakers with cleft palate may demonstrate for nasal sounds. Nasal sounds, ideally in different vowel contexts, should be included in articulation screenings for speakers with cleft palate, perhaps more than is currently the case.

Speaking Tongues Are Actively Braced

PURPOSE

Bracing of the tongue against opposing vocal-tract surfaces such as the teeth or palate has long been discussed in the context of biomechanical, somatosensory, and aeroacoustic aspects of tongue movement. However, previous studies have tended to describe bracing only in terms of contact (rather than mechanical support), and only in limited phonetic contexts, supporting a widespread view of bracing as an occasional state, peculiar to specific sounds or sound combinations.

METHOD

The present study tests the pervasiveness and effortfulness of tongue bracing in continuous English speech passages using electropalatography and 3-D biomechanical simulations.

RESULTS

The tongue remains in continuous contact with the upper molars during speech, with only rare exceptions. Use of the term bracing (rather than merely contact) is supported here by biomechanical simulations showing that lateral bracing is an active posture requiring dedicated muscle activation; further, loss of lateral contact for onset /l/ allophones is found to be consistently accompanied by contact of the tongue blade against the anterior palate. In the rare instances where direct evidence for contact is lacking (only in a minority of low vowel and postvocalic /l/ tokens), additional biomechanical simulations show that lateral contact is maintained against pharyngeal structures dorsal to the teeth.

CONCLUSION

Taken together, these results indicate that tongue bracing is both pervasive and active in running speech and essential in understanding tongue movement control.

Magnetic resonance imaging of the brain and vocal tract: Applications to the study of speech production and language learning

The human vocal system is highly plastic, allowing for the flexible expression of language, mood and intentions. However, this plasticity is not stable throughout the life span, and it is well documented that adult learners encounter greater difficulty than children in acquiring the sounds of foreign languages. Researchers have used magnetic resonance imaging (MRI) to interrogate the neural substrates of vocal imitation and learning, and the correlates of individual differences in phonetic "talent". In parallel, a growing body of work using MR technology to directly image the vocal tract in real time during speech has offered primarily descriptive accounts of phonetic variation within and across languages. In this paper, we review the contribution of neural MRI to our understanding of vocal learning, and give an overview of vocal tract imaging and its potential to inform the field. We propose methods by which our understanding of speech production and learning could be advanced through the combined measurement of articulation and brain activity using MRI - specifically, we describe a novel paradigm, developed in our laboratory, that uses both MRI techniques to for the first time map directly between neural, articulatory and acoustic data in the investigation of vocalisation. This non-invasive, multimodal imaging method could be used to track central and peripheral correlates of spoken language learning, and speech recovery in clinical settings, as well as provide insights into potential sites for targeted neural interventions.

Lateral bracing of the tongue during the onset phase of alveolar stops: an EPG study

Although raising the sides of the tongue to form a seal with the palate and upper teeth--lateral bracing--plays a key role in controlling airflow direction, providing overall tongue stability and building up oral pressure during alveolar consonant production, details of this articulatory gesture remain poorly understood. This study examined the dynamics of lateral bracing during the onset of alveolar stops /t/, /d/, /n/ produced by 15 typical English-speaking adults using electropalatography. Percent tongue palate contact in the lateral regions over a 150-ms period from the preceding schwa to stop closure was measured. Rapid rising of the sides of the tongue from the back towards the front during the 50-ms period before closure was observed, with oral stops showing significantly more contact than nasal stops. This feature corresponds to well-documented formant transitions detectable from acoustic analysis. Possible explanations for increased contact for oral stops and clinical implications are discussed.

Electropalatographic specification of Croatian fricatives /s/ and /z/

Electropalatographic specification of alveolar fricatives in Croatian is aimed at providing speech therapists with normative data about the range of acceptable productions of /s/ and /z/ in adult speakers of Croatian. Four variables were analysed: place of articulation, total contact, groove width and hold phase duration. Intra- and inter-speaker variability for each variable was analysed. Lingual palatal cues for voicing difference were also quantified and discussed. Results show that Croatian /s/ and /z/ are alveolar and not dental as previously reported. The comparison between the voiced and the voiceless fricative shows that durational measures provide the best differentiation. The voiceless counterpart is significantly longer. The difference between voiced and voiceless is also found in the total contact, with /z/ having more contact in the anterior four rows of electrodes, while /s/ has more contact in the posterior four rows of electrodes. This difference is also reflected in the anterior and the posterior groove widths. Possibilities of using these results as normative data for the diagnosis and treatment of atypical articulation of /s/ and /z/ are discussed.

Sherlock Holmes and the strange case of the missing attribution: a historical note on "The Grandfather Passage"

PURPOSE

In 1963, Charles Van Riper published "My Grandfather," a short reading passage that has evolved into a ubiquitous metric of reading ability and speech intelligibility. In this historical note, we describe several heretofore unacknowledged similarities between "The Grandfather Passage" (Darley, Aronson, & Brown, 1975) and a portion of The Valley of Fear (Conan Doyle, 1915/2006), the final novel of the Sherlock Holmes series. We also describe overlap between "My Grandfather" and "The Grandfather Passage."

METHOD

We contrasted propositions within The Valley of Fear to "My Grandfather" and "The Grandfather Passage." We also compared the respective text strings using the Turnitin antiplagiarism software application (iParadigms, 2011).

RESULTS

"My Grandfather" and "The Grandfather Passage" are nearly identical passages with 88% string overlap. In addition, both passages show similarities with text from The Valley of Fear.

CONCLUSIONS

Darley et al. (1975) did not acknowledge Van Riper (1963) as the original author of "The Grandfather Passage." In addition to this citation oversight, neither Darley et al. nor Van Riper attributed Conan Doyle as original source material. We describe the colorful history of this passage that has seen a remarkable breadth of utility in speech and language sciences.

Phonetic description of alveolar phones using electropalatography

PURPOSE

To describe the articulation of the Brazilian Portuguese, by examining the tongue-palate contact in the production of consonantal phones.

METHODS

The electropalatography (EPG) of the alveolar consonants of the Brazilian Portuguese produced by an individual with typical speech was used, considering the alveolar, post-alveolar, palatal, and velar rates, as well as the percentage of activated contacts at the point of maximum constriction, and the visual inspection of palatograms.

RESULTS

As expected, it was observed that all the examined phones have more contact in the alveolar region at the point of maximum constriction. The phones /t/, /d/ and /n/ showed more alveolar contact, with total obstruction of the air stream; the fricative phones /s/ and /z/ were characterized by the absence of contact at the central longitudinal axis; the lateral phone /l/ did not present contact at the lateral longitudinal axis, and the tap /[symbol: see text]/ showed not only few tongue-palate contacts but it was also produced in the shortest duration time.

CONCLUSION

The electopalatography allowed a detailed description of the extension of the tongue-palate contact in the different alveolar phones of the Brazilian Portuguese and how they occur.

Adaptation to an electropalatograph palate: acoustic, impressionistic, and perceptual data

PURPOSE

The purpose of this study was to evaluate adaptation to the electropalatograph (EPG) from the perspective of consonant acoustics, listener perceptions, and speaker ratings.

METHOD

Seven adults with typical speech wore an EPG and pseudo-EPG palate over 2 days and produced syllables, read a passage, counted, and rated their adaptation to the palate. Consonant acoustics, listener ratings, and speaker ratings were analyzed.

RESULTS

The spectral mean for the burst (/t/) and frication (/s/) was reduced for the first 60-120 min of wearing the pseudo-EPG palate. Temporal features (stop gap, frication, and syllable duration) were unaffected by wearing the pseudo-EPG palate. The EPG palate had a similar effect on consonant acoustics as the pseudo-EPG palate. Expert listener ratings indicated minimal to no change in speech naturalness or distortion from the pseudo-EPG or EPG palate. The sounds [see text] were most likely to be affected. Speaker self-ratings related to oral comfort, speech, tongue movement, appearance, and oral sensation were negatively affected by the presence of the palatal devices.

CONCLUSIONS

Speakers detected a substantial difference when wearing a palatal device, but the effects on speech were minimal based on listener ratings. Spectral features of consonants were initially affected, although adaptation occurred. Wearing an EPG or pseudo-EPG palate for approximately 2 hr results in relatively normal-sounding speech with acoustic features similar to a no-palate condition.