Electropalatography Research Articles

Influence of a Standard Electropalatography Artificial Palate Upon Articulation

Objective: This study investigated the influence of a standard electropalatography (EPG) palate upon speech articulation in 3 normal speakers under standard EPG testing conditions. Patients and Methods: Three adult females aged 26, 31 and 34 years read the experimental phrase ‘say CV again’ 5 times under 3 experimental conditions: normal speech (without a palate in situ), 45 min after EPG palate insertion and 3 h after EPG palate insertion. Consonants and vowels commonly used in EPG research were studied and included /t/, /s/ and /∫/ in the /i/, /a/ and /u/ vowel environments. Perceptual and acoustic analysis of the data was completed. Results: The results revealed varied patterns of adaptation across the 3 participants. Perceptual analysis suggested that 2 of the participants adapted to the presence of the palate; however, 1 did not. The presence of the palate resulted in significant changes to consonant duration for all 3 participants. Spectrally, production of /t/ was unaffected by the presence of the palate, while articulation of fricatives varied across the participants. Conclusion: Paired with a previous study examining the effects of an EPG palate upon speech articulation [McLeod S, Searl J: Am J Speech Lang Pathol 2006;15:192–206], the present data suggest that researchers and clinicians alike should be aware of the potential perturbing effects of the palate.

Tongue palate contact patterns of velar stops in normal adult English speakers

This paper provides a more detailed description of normal tongue palate contact patterns for the occlusion phase of velar stops than currently exists. The study used electropalatography (EPG) to record seven normally speaking adults' contact patterns of voiceless velar stops in nine VkV contexts. A variety of EPG indices measured: per cent complete closures across the palate; place of articulation; articulatory distance between /k/ and /t/; and amount of contact. Complete EPG closure occurred in the majority (81%) of tokens. Some speakers almost always had complete closures regardless of context, whereas other speakers produced them only with high front vowels. As expected, place of articulation and amount of contact were heavily influenced by vowel context. The most fronted and most contact occurred in /i/ contexts and the most retracted and least contact in /a/ contexts. There was considerable interspeaker variability on all measures, particularly in the precise location of velar placement and articulatory distance between alveolar and velar placement. The implications for diagnosing and treating abnormal velar articulations are discussed.

Electropalatographic (EPG) assessment of tongue‐to‐palate contacts in dysarthric speakers following TBI

The aim of the investigation was to compare EPG‐derived spatial and timing measures between a group of 11 dysarthric individuals post‐severe TBI and 10 age‐ and sex‐matched neurologically non‐impaired individuals. Participants of the TBI group were diagnosed with dysarthria ranging from mild‐to‐moderate–severe dysarthria. Each participant from the TBI and comparison group was fitted with a custom‐made artificial acrylic palate that recorded lingual palatal contact during target consonant production in sentence‐ and syllable‐repetition tasks at a habitual rate and loudness level. Analysis of temporal parameters between the comparison and TBI groups revealed prolonged durations of the various phases of consonant production, which were attributed to articulatory slowness, impaired speech motor control, impaired accuracy, and impaired coordination of articulatory movements in the dysarthric speakers post‐TBI. For the spatial measurements, quantitative analysis, as well as visual inspection of the tongue‐to‐palate contact diagrams, indicated spatial aberrations in dysarthric speech post‐TBI. Both the spatial and temporal aberrations may have at least partially caused the perceptual judgement of articulatory impairments in the dysarthric speakers.

Unresolved issues in the representation and phonetic description of click articulation in Xhosa and Zulu

The paper addresses three issues that are regarded as unresolved with respect to the representation and description of click sounds in Xhosa and Zulu. These issues relate to (i) different phonetic transcription systems for clicks, (ii) a controversy regarding the specification of places of articulation for clicks, and (iii) the phonetic content of socalled ‘noisy’ or affricated clicks. Current practices regarding the use of the revised IPA symbols for clicks are discussed against the backdrop of experimental phonetic results on click articulations as obtained through electropalatographic (EPG) techniques. It is argued that the use of the symbols usually used for velar stops as components of a click representation is unfounded and that it actually obscures other salient features of click articulations. A simplified system is proposed for Bantu languages such as Zulu and Xhosa. The place of articulation of palatal clicks in Zulu is confirmed through the presentation of EPG data linking it to the [!] phonetic symbol that is more generally used to denote alveolar clicks. The traditional views on the phonetic content of noisy (affricated) dental and alveo-lateral clicks are challenged in view of data obtained through an innovative speech processing technique (Smoothed Pseudo-Wigner Distribution Analysis) that combines the good frequency resolution of narrow band spectrograms and the good time resolution of wide band spectrograms. It is shown that these sounds are not affricated, but in fact pre-affricated and that traditional interpretations of waveforms are incorrect.

Changes in acoustic characteristics of /r/ following production training using electropalatography (EPG)

Visual feedback using electropalatography (EPG) is an effective method for changing production of speech sounds in children. Differences in tongue placement and general acceptability of production have been demonstrated with EPG training for tongue to palate contact. Little is known, however, about changes in the spectral characteristics of speech sounds following training. The current study examined pre and post EPG patterns for /r/ in prevocalic, intervocalic, and postvocalic positions in sentences with five weeks of intensive EPG training. In particular, spectral characteristics of /r/ were examined for differences pre and post treatment. Subjects were four children (aged 9–10). These children exhibited distorted /r/ despite several years of traditional speech therapy but learned to produce perceptually acceptable /r/ with EPG. Spectral characteristics for /r/ productions in the same sentences by four typically developing children were used for comparison. Differences will be discussed in terms of acoustic characteristics as well as changes in tongue position.

Electropalatographic Assessment of Tongue-to-Palate Contact Patterns and Variability in Children, Adolescents, and Adults

To investigate the developmental time course of tongue-to-palate contact patterns during speech from childhood to adulthood using electropalatography (EPG) and a comprehensive profile of data analysis. Tongue-to-palate contacts were recorded during productions of /t/, /l/, /s/, and /k/ in 48 children, adolescents and adults (aged 6-38 years) using the Reading Electropalatograph system. A protracted course of development for lingual control was indicated, with significant changes occurring until age 11 years; the adolescent period was in turn characterized by continual refinement of articulatory control. With maturity, a reduction in the amount of palatal contact and an anterior shift in the place of articulation was evident during anterior consonant productions, whereas the tongue-back-to-palate contact pattern became more consistent for the velar stop /k/. These results support that maturation of the speech motor system is nonuniform.

Tongue-Palate Contact during Bilabials in Normal Speech

Previous research using electropalatography (EPG) identified a compensatory articulation called bilabial-lingual double articulations. These double articulations were produced for bilabials by some speakers with cleft palate and involved closure at the lips occurring simultaneously with complete tongue-palate constriction. However, no normative English EPG data exist to confirm the abnormal status of these double articulations. This study reports normative data for EPG contact during bilabial closure. Acoustic and EPG data were recorded for bilabials in different vowel contexts. Eight normal English-speaking adults. One measure identified complete tongue-palate constriction, and a second measure calculated percent contact. There were no instances of complete tongue-palate constriction, though some EPG contact occurred in the lateral regions of the palate. The vowel context significantly affected the amount of contact present, with /i/ having the most and /a/ having the least amount of contact. Complete tongue-palate constriction during bilabials of the type found in bilabial-lingual double articulations is not a feature of normal English speech and can therefore be considered an abnormal articulation pattern. Speech-language pathologists who use EPG in their clinical work should be aware that some lateral contact during bilabial closure is normal.

Evaluating a new clinical palatometry system

EPG (Electropalatography) is a visual feedback device designed for clinical and research applications centered on articulation in terms of tongue-to-hard palate contact. EPG has been shown to be effective for a range of speech sound disorders. Several EPG systems have been marketed. One factor that has limited access to EPG treatment, especially in a clinical setting, is the cost of manufacturing the pseudopalates. A new EPG system from Logometrix utilizes a glued on strip of electrodes rather than individually placed electrodes, significantly reducing production expense. Clinical use of the new EPG system is reviewed for 13 clients with varying speech sound disorders, for whom EPG was beneficial in phonetic treatment. Two children were unable to tolerate the pseudopalates, suggesting that practice palates without electrodes be utilized.

Electropalatography and ultrasound in vowel remediation for adolescents with hearing impairment

The purpose of this study was to investigate the use of electropalatography (EPG) and ultrasound in the remediation of vowels in adolescents with hearing impairment. Three adolescents with severe hearing impairment participated in a 6-week vowel remediation programme using electropalatography (EPG) and dynamic two-dimensional ultrasound as adjuncts to speech therapy. Pre- and post-therapy speech productions were evaluated in terms of vowel formant values, EPG tonguepalate contact patterns and phonetic transcription. Notable changes were observed for all vowels across speakers, with most changes in the direction of the adult English targets. Transcription, acoustic and EPG tongue-palate contact results did not necessarily converge across vowels or speakers. Visual feedback as provided by EPG and ultrasound can be facilitative in promoting vowel development in adolescents with hearing impairment. Further research is required to evaluate the stability of changes, the relative impact of ultrasound and EPG and the relationship between phonetic transcriptions, tongue-palate contact and acoustic information about vowels.

Electropalatography home training using a portable training unit for Japanese children with cleft palate

The primary objective of this study was to determine the effectiveness of electropalatography (EPG) home training using a portable training unit (PTU) for clients with residual articulation disorders. The participants were five Japanese children with cleft lip and palate ranging in age from 8 to 13 years when they began EPG home training. These children had residual articulation disorders caused by abnormal tongue-palate contact, although four of them had received conventional speech therapy for 3 to 8 years before starting EPG training. The WinEPG system (Articulate Instruments, Edinburgh) was used to make recordings during the initial assessment and the monthly follow-up. The participants received EPG training sessions when they attended for their monthly recordings. A training programme was developed for each participant, and they were instructed to carry out their homework assignments using the PTU. After 7 to 9 months of home training, marked changes in the EPG patterns and “centre of gravity” values...

Articulatory characteristics of the occlusion phase of /t/ compared to /t/ in adult speech

This study used electropalatography (EPG) to investigate articulatory characteristics of /t/ and /t/ occlusion in order to provide normative data to be used for the diagnosis and treatment of individuals with speech disorders. EPG data from the EUR-ACCOR database were analysed for nonsense VCV sequences containing /t/ and /t/ in nine vowel contexts for seven English speaking adults. The main results of this study are that all speakers had a significantly more posterior placement for /t/ compared to /t/ and that placement was stable during the occlusion phase of both /t/ and /t/. For most speakers, the occlusion phase was longer for /t/ compared to /t/, the occlusion phase generally involved more EPG contact and was slightly more variable in /t/ compared to /t/, but these differences were not statistically significant for all speakers. The implications of the results for diagnosing and treating speech disorders are discussed.

The national CLEFTNET project for individuals with speech disorders associated with cleft palate

Although previous studies have demonstrated the benefits of using electropalatography (EPG) for treating therapy-resistant articulation errors associated with cleft palate, until recently access to this form of treatment has been limited. For the past 10 years, however, the CLEFTNET Scotland project has provided individuals with cleft palate access to EPG therapy. CLEFTNET Scotland represented a novel form of EPG service delivery—it linked the cleft palate centres throughout Scotland to Queen Margaret University College (QMUC) in Edinburgh through an electronic network. EPG data collected in the centres were sent to QMUC, where experts conducted detailed analysis leading to a precise diagnosis of each individual's specific articulation difficulty and suggested therapy guidelines to the specialist speech-language therapists based on their analysis. This form of service delivery has recently extended to include England, Wales and Northern Ireland to form CLEFTNET UK. This paper describes the CLEFTNET projec...

Normal adult speakers' tongue palate contact patterns for alveolar oral and nasal stops

This study compared tongue palate contact patterns for oral stops (/t/, /d/) with those for the nasal stop /n/ in order to provide normative data for diagnosing and treating individuals with speech disorders. Electropalatographic (EPG) data were recorded from 15 English speaking adults for word initial /t/, /d/ and /n/ in a high and a low vowel context. EPG frames were classified according to three criteria: (1) anterior constriction; (2) bilateral constriction; and (3) zero posterior central contact. Total amount of contact and variability were also measured. The results showed that almost all (99%) stops met Criteria 1 and 3, with fewer articulations (88% of /t/; 83% of /d/ and 55% of /n/) meeting Criterion 2. Although all stops had similar spatial patterns, /t/ and /d/ had more contact and were more likely to have bilateral constriction than /n/. There were no differences in variability between /t/, /d/ and /n/, however. The clinical implications of the results for the management of individuals with sp...

Acoustic and perceptual analysis of speech adaptation to an artificial palate

The study investigated adaptation to a standard electropalatographic (EPG) practise palate in a group of eight adults (mean age = 24 years). The participants read the phrase “a CVC” over four sampling conditions: prior to inserting the palate, immediately following insertion of the palate, 45 minutes after palate insertion, and 3 hours after insertion of the palate. Perceptual and acoustic analyses were conducted on the initial CV portion of the stimuli. Consonants examined included: /t/, /k/, /s/, and /∫/ followed by the /i/, /a/, and /u/ vowels. Results revealed that individuals within the group were able to adapt their speech articulation to compensate for the presence of the artificial palate. Perceptually, mild consonant imprecision was observed upon insertion of the palate; however, this resolved following 45 minutes to 3 hours of adaptation. Acoustic findings indicated that the palate did not affect segment durations or vowel formant frequencies. However, a significant reduction in M1 for /s/ persisted across the sampling periods. Overall, the results suggest that a period of between 45 minutes and 3 hours of adaptation is generally suitable for participation in EPG studies.

Treatment with a combination of intra-oral sensory stimulation and electropalatography in a child with severe developmental dyspraxia

This paper describes the use of a combination of intra-oral sensory stimulation and electropalatography (EPG) in the treatment of a case with severe developmental verbal dyspraxia. A multiple-baseline design was used. The treatment duration was 11 months and started when the subject was 5 years old. The efficacy of the treatment was assessed by calculations of percentage of correctly articulated words, percentage of consonants correct, percentage of phonemes correct and percentage of words correct. Intelligibility assessments were conducted by both naïve and expert listeners. The experts also assessed visual deviances in articulatory gestures from video recordings. Qualitative analysis of EPG data was made. The subject's speech was significantly improved by the treatment in all aspects. The results and their generalization to other cases of developmental verbal dyspraxia are discussed.

Understanding speech production using electropalatography

The papers in this special issue of Advances in Speech- Language Pathology were originally delivered at the 4th International Electropalatography (EPG) Symposium, held in Edinburgh in September 2005.

The quantification of place of articulation assimilation in electropalatographic data using the similarity index (SI)

The present study is concerned with an electropalatographic (EPG) and acoustic analysis of coarticulatory influences in fricative consonant clusters that span a word boundary. We aimed to test whether, as has been found for other languages and consonant-classes, final consonants are more prone to coarticulatory influences than initial ones, and also whether there is any evidence for a relationship between a consonant’s susceptibility to coarticulation and the extent to which it exerts a coarticulatory influence on flanking consonants. We developed an algorithm, the similarity index (SI), which quantifies coarticulation in EPG data by measuring the extent of deviation of consonants in heterorganic clusters from their homorganic counterparts. This algorithm was applied to EPG data recorded from three native speakers of Polish producing word-pairs in a carrier sentence such that word-final and word-initial fricatives occurred across a word-boundary for all 16 possible combinations of the four fricatives [ ]. The same data were analysed acoustically using Bark-scaled cepstral coefficients. The results showed that word-final consonants were more susceptible to coarticulatory influences than were initial ones; and there was some evidence that the alveolopalatal fricative [ ] was most resistant to coarticulation, and exerted the greatest coarticulatory influences.

Temporal and spatial aspects concerning the realizations of the voicing contrast in German alveolar and postalveolar fricatives

This study investigates the phonetic realizations of voicing contrast in alveolar and postalveolar fricatives production in different word positions in order to understand the temporal and spatial production strategies used in the control of voicing and frication, and to provide a frame of reference for speech therapy despite the inter-speaker variation. Seven native speakers of German, originally coming from various regions, participated in the experiment. Acoustic signals were recorded onto DAT, and tongue palate contact patterns were recorded by means of electropalatography (EPG). The temporal parameters were measured using the acoustic signals and the spatial parameters were measured based on the EPG data. The corpus included real words with // occurring at word initial, medial and final positions. Temporal results showed that differences in the overall frication duration for voicing contrast occur at almost all positions (with longer duration for voiceless phonemes). However, voicing during the frica...

Intra-participant variability in Parkinson's disease: An electropalatographic examination of articulation

The articulation of individuals with dysarthria has traditionally been described as consistent. However, conflicting findings have resulted from research examining intra-participant variation in the articulation of individuals with Parkinson's disease (PD) and hypokinetic dysarthria. The current study used electropalatography (EPG) to examine the degree of intra-participant variation in both tongue-palate contact patterns and duration of contact in a group of speakers with PD and hypokinetic dysarthria including consonant imprecision (n = 8). The study also aimed to determine if ageing contributed to any articulatory instability observed. Therefore, two control groups were employed consisting of aged adult (n = 7) and young adult (n = 8) speakers respectively. Participants were asked to read aloud the phrase “I saw a CVC today” were C = /t/, /s/, and /l/ and V = /a/. Intra-participant variation in tongue-palate contact was measured using the absolute and relative variability indexes. Coefficients of varia...

Advances in EPG palate design

Electropalatography (EPG) is a highly effective tool for speech research and for the diagnosis and treatment of a range of speech disorders. The technique requires an EPG palate to be custom made for each user. The manufacture of the palate is both costly and time consuming and inhibits wider uptake of the technique. This paper undertakes a thorough re-examination of all aspects of EPG palate design including criteria for selecting the number and location of contacts, materials properties, costs and safety issues. Palate design over the last 30 years is reviewed and a new design (the Articulate palate) is proposed based on the findings, which minimizes cost while maximizing comfort, safety, convenience, reliability and accuracy.