Vowel Triangle Research Articles

Vowel production: a potential speech biomarker for early detection of dysarthria in Parkinson's disease.

Our aim is to detect early, subclinical speech biomarkers of dysarthria in Parkinson's disease (PD), i.e., systematic atypicalities in speech that remain subtle, are not easily detectible by the clinician, so that the patient is labeled "non-dysarthric." Based on promising exploratory work, we examine here whether vowel articulation, as assessed by three acoustic metrics, can be used as early indicator of speech difficulties associated with Parkinson's disease. This is a prospective case-control study. Sixty-three individuals with PD and 35 without PD (healthy controls-HC) participated in this study. Out of 63 PD patients, 43 had been diagnosed with dysarthria (DPD) and 20 had not (NDPD). Sustained vowels were recorded for each speaker and formant frequencies were measured. The analyses focus on three acoustic metrics: individual vowel triangle areas (tVSA), vowel articulation index (VAI) and the Phi index. tVSA were found to be significantly smaller for DPD speakers than for HC. The VAI showed significant differences between these two groups, indicating greater centralization and lower vowel contrasts in the DPD speakers with dysarhtria. In addition, DPD and NDPD speakers had lower Phi values, indicating a lower organization of their vowel system compared to the HC. Results also showed that the VAI index was the most efficient to distinguish between DPD and NDPD whereas the Phi index was the best acoustic metric to discriminate NDPD and HC. This acoustic study identified potential subclinical vowel-related speech biomarkers of dysarthria in speakers with Parkinson's disease who have not been diagnosed with dysarthria.

An Investigation into the Vowel Space Area and Vowel Intelligibility among English-speaking Children with Cochlear Implant in India

Abstract Background: Literature does show that studies of the vowel space area (VSA) can be helpful to know speech production skills in children with hearing impairment (HI) cochlear implant (CI). The need for the present study was to investigate speech production skills among children with CI, who receive Aural Rehab in nonnative language, i.e., English. The VSA offers an easy quick way to compare speech production accuracy among them to typically developing chidlren (TDC) peer group. Aim of the Study: The study aimed at investigating the VSA in F2 versus F1 space formed by vowels /a/, /i/, and /u/ in two groups of children (typically developing [TD] and children with CIs) and the intelligibility of the vowels spoken in the consonant-vowel-consonant (CVC) contexts. Methods: Two groups of subjects participated in the study, 100 children with CIs and 200 age-matched typically developing children. Recordings of vowels /a/, /i/, and /u/ in CVC were used for formant frequency extraction using Praat software, and the VSA was calculated. The recorded utterances were presented to three judges, for the estimation of the percentage of correct responses for identifying the vowel. The VSA for the vowels and the intelligibility scoring in percentage were valuated. Results: The results showed that the VSA among children with CI was significantly less compared to TDC. The reduced VSA represents limited articulatory movement in children with CI compared to children with TD for primary vowels embedded in CVC syllables. The vowel intelligibility for the three vowels in the CVC context was reduced for children with CI (70%) compared to that of children with TDC (95%). Discussion: Both first- and second-formant frequencies show distinct differences between both groups and consequently in the VSA. F1 is lower for /a/ for the CI group, while it is higher for vowel /i/ and /u/ for the CI group compared to the TDC group, while F2, the values were lower for /i/ but elevated significantly for both /a/ and /u/ compared to children in TDC. The intelligibility of their utterances (CVC) of children with CI was lower than that of TDC. Since the children were age- and gender-matched and were nonnative speakers of English, linguistic influences on measured values were minimum. Reasons for changed formant frequencies have to be explored further in terms of the influence of rehabilitation methods, visibility of articulatory movements required, and formant information coded by speech coding strategies. Correlation studies of the VSA and the speech intelligibility measures may assist in therapy outcomes and improve speech intelligibility in children with HI and modifications to mapping strategies employed. Conclusion: The F1 is lower for /a/ for the CI group, while it is higher for vowel /i/ and /u/ for the CI group compared to the TDC group, while F2, the values were lower for /i/ but elevated significantly for both /a/ and /u/ compared to children in TDC. The vowel triangle area was reduced in the speech of CI group subjects compared to that of the group of TDC.

국어교사의 발음 명료도 분석

Objectives The purpose of this study is to propose the necessity and to provide information for Korean teacher's pronunciation education by examining the pronunciation clarity of Korean teacher by analyzing Korean teacher's pronunciation of [i], [u], and [a]. Methods To this end, in this study, the characteristics of pronunciation clarity of Korean teachers were examined by collecting voice data of 82 Korean teachers, analyzing F1 and F2 of the vowels, and displaying F1 and F2 coordinates on a two-dimensional plane to calculate the Euclidean distance and the width of vowel triangle. In addition, Korean language teachers were classified by gender and career to examine whether there were differences in pronunciation clarity by group. Results First, it was found that F1, F2 for the pronunciation of [i], [u], [a] of Korean language teachers showed a similar tendency to general Korean speakers. Second, it was found that Korean language teachers had lower pronunciation clarity than general Korean speakers. Third, it was found that female teachers clarified their pronunciation compared to male teachers. Fourth, it was found that the difference in pronunciation clarity according to the career of a Korean language teacher was not large. Conclusions It is necessary to operate an educational program to increase the pronunciation clarity of teachers in the teacher training and teacher re-education process. In particular, pronunciation education for male teachers needs to be concentrated rather than female teachers, and education programs need to be organized so that Korean teachers with more than 10 years of experience can clearly pronounce [u].

Vowel acoustics of Nungon child-directed speech, adult dyadic conversation, and foreigner-directed monologues.

In many communities around the world, speech to infants (IDS) and small children (CDS) has increased mean pitch, increased pitch range, increased vowel duration, and vowel hyper-articulation when compared to speech directed to adults (ADS). Some of these IDS and CDS features are also attested in foreigner-directed speech (FDS), which has been studied for a smaller range of languages, generally major national languages, spoken by millions of people. We examined vowel acoustics in CDS, conversational ADS, and monologues directed to a foreigner (possible FDS, labeled MONO here) in the Towet dialect of the Papuan language Nungon, spoken by 300 people in a remote region in northeastern Papua New Guinea. Previous work established that Nungon CDS entails optional use of consonant alteration, special nursery vocabulary, and special morphosyntax. This study shows that Nungon CDS to children aged 2;2–3;10 lacks vowel hyper-articulation, but still displays other common prosodic traits of CDS styles around the world: increased mean pitch and pitch range. A developmental effect was also attested, in that speech to 2-year-olds contained vowels that were significantly longer than those in speech to 3-year-olds, which in turn had vowels of similar duration to those in Nungon ADS. We also found that Nungon FDS vowel triangles, measured from monologues primarily directed to a non-native speaker, were significantly larger than those of either CDS or conversational ADS, indicating vowel hyper-articulation. The Nungon pattern may align with the patterns of vowels in Norwegian IDS, CDS, and FDS, where hyper-articulation is found in FDS, but not CDS or IDS. The languages of the New Guinea area constitute 20% of the world's languages, but neither an acoustic comparison of vowels in CDS and ADS, nor an acoustic study of FDS, has previously been completed for any language of New Guinea. The function of an FDS style in a small, closed community like those of much of New Guinea may differ from that in larger societies, since there are very few non-native speakers of Nungon. Thus, this study uses monologues recorded with a foreign researcher as interlocutor to study Nungon FDS.

Parents tune their vowels to the emergence of children's words.

The aim of this study was to investigate the acoustic vowel space area in infant directed speech (IDS). The research question is whether the vowel space is expanded or remains constant in IDS. A corpus of spontaneous interactions of 9 dyads followed monthly from the age of 6 to 24 months was analyzed. The occurrences in the parents' speech of each word that the children eventually acquired were extracted. The surface of the vowel triangle and the convex hull of all vowels were computed. The main result is that the development of the vowel space in IDS follows an inverted U-shaped curve: the vowel space starts relatively small, gradually increases as the child's first word use approaches, and decreases again afterwards. These findings show that parents adapt their articulation to the evolving linguistic abilities of their child, and this adaptation can be detected at the level of individual lexical items.

Study of the Role of Hearing Aid on the Area of the Acoustic Field of Vowels.

The method of transformation of acoustic vowel triangles (AVT) /a/, /i/, /u/ was used for an objective assessment of the acoustic features of vowels in the speech production of 20 persons with long-term hearing impairment (LHI). The logarithm of the values ​​of the first two formants of each vowel (logF1, logF2) was determined for each subject. AVTs were transformed into the right-angled triangles, the vertices of the sound /u/ of which were moved to the origin of coordinates and the legs were aligned with the coordinate axes. In patients with LHI, the size of the triangles usually decreased, and they were stretched along one of the axes, which probably depends not only on the hearing loss severity but also on the duration of hearing aid use. The presented approach to the normalization of AVTs makes it possible to distinguish at least three groups of persons with LHI: in the first group, vowel triangles are stretched along the logF1 axis; in the second group, vowel triangles are stretched along the logF2 axis; and in the third group, AVT are symmetric.

Dynamics of vowel acoustic space indicators in patients with long-term hearing loss

To characterize VAS of adult Russian speakers with long-term HL using newly developed acoustic indicators. Recordings of sustained Russian cardinal vowels /a/, /i/, /u/ of 10 women and 10 men with long-term HL were acoustically analyzed. For each participant, two first formants of each vowel were measured and log-transformed (logF1, logF2). VAS was transformed into right triangles, their /u/ corners were moved to the origin, and their legs were aligned with axes. VAS was almost symmetrical, equal and have a maximum size in the control group consisted of subjects without hearing impairment while these of long-term HL group VAS size tended to have reduced and VAS stretched along one axis. Our study showed that a new VAS normalization approach can distinguish at least three groups of people with long-term HL. There are those with vowel triangles stretched along logF1-axis, with vowel triangles stretched along logF2-axis, and with symmetrical vowel triangles. Causes of the VAS differences require further investigation.

Characterization of Parkinson’s disease dysarthria in terms of speech articulation kinematics

Speech is a vehicular tool to detect neurological degeneration using certain accepted biomarkers derived from sustained vowels, diadochokinetic exercises or running speech. Classically the Vowel Space Area (VSA) and the Formant Centralization Ratio (FCR) have been proposed to describe dysarthria in Parkinson’s Disease (PD). These features are based in global estimations of the positions of the first two formants in the representation of a vowel triangle. The aim of the paper is to give a description of speech articulation dynamics as a probability density function of the kinematic features derived from the evolution of formants in the time domain. The statistical distribution of the dynamic behavior of articulation features can be used to estimate differences between speech features from subjects with Parkinson’s dysarthria relative to normative subjects. Utterances of vowels [a:, i:, u:] from a subset of 16 subjects with PD (8 males and 8 females), confronted to a subset of 16 normative subjects (8 males and 8 females) have shown that the statistical distributions of dynamic articulation features can be differentiated using information theory based estimations such as Kullback-Leibler and Jensen-Shannon Divergence (JSD). These estimations allow establishing relevant statistical differences between PD and normative subjects both for males and females, improving the differentiation capability of VSA and FCR.

Quality and quantity of infant-directed speech by maternal caregivers predicts later speech-language outcomes in children with cochlear implants

Caregivers speaking to children often adjust segmental and suprasegmental qualities of their speech relative to adult-directed (AD) speech. The quality and quantity of infant-directed (ID) speech has been shown to support word learning and word segmentation by normal-hearing infants, but the extent to which children with cochlear implants (CIs) benefit linguistically from ID speech is unclear. The present study investigated the extent to which the quantity and quality of ID speech produced in the lab by each of 40 mothers to her child with a CI predicted the child’s speech-language outcome measures at two years post-implantation. Multiple measures of ID and AD speech for each mother were taken, including ID speech quantity in one minute, and several measures of ID speech quality, including fundamental frequency characteristics, speech rate, and the area of the vowel triangle formed by corner vowels in F1-F2 space. Forward stepwise regression showed that both quantity and quality of speech significantly predicted language outcomes measured by the Preschool Language Scales, Peabody Picture Vocabulary Test, and the Reynell Developmental Language Scales. These results support the hypothesis that hearing more ID speech that has acoustic modifications typical of IDS promotes language proficiency in children with CIs.

Monitoring Parkinson Disease from speech articulation kinematics

Parkinson Disease (PD) is a neuromotor illness affecting general movements of different muscles, those implied in speech production being among them. The relevance of speech in monitoring illness progression has been documented in these last two decades. Most of the studies have concentrated in dysarthria and dysphonia induced by the syndrome. The present work is devoted to explore how PD affects the dynamic behavior of the speech neuromotor biomechanics (neuromechanics) involved in deficient articulation (dysarthria), in contrast to classical measurements based on static features as extreme and central vowel triangle positions. A statistical distribution of the kinematic velocity of the lower jaw and tongue is introduced, which presents interesting properties regarding pattern recognition and classification. This function may be used to establish distances between different articulation profiles in terms of information theory. Results show that these distances are correlated with a set of tests currently used by neurologists in PD progress evaluation, and could be used in elaborating new speech testing protocols.

Reconceptualizing the vowel space in analyzing regional variation

Vowel space area calculated on the basis of the corner vowels has emerged as a metric for the study of regional variation, speech intelligibility, and speech development. We verify the basic assumptions underlying both the concept of the vowel space and the utility of the vowel space area in making speaker, dialect, or language comparisons. Undeniably, the traditional vowel triangle and vowel quadrilateral both fail as a metric in the context of dialect variation because substantial parts of the actual working space are excluded from analysis. Utilizing the formant values at a number of different locations for a wider range of individual vowels has significant implications for the size and shape of the resulting vowel space. Indeed, dialectal variations in vowel production can best be characterized in terms of formant density regions in the formant space and not as locations of individual vowel categories. The formant density approach is based on the assumption that vowel sounds are dynamically changing multidimensional units, which naturally overlap in the acoustic space. The formant density approach is able to minimize the amount of empty space within the overall shape while still respecting the outer boundary of the dataset.

Finding the Most Uniform Changes in Vowel Polygon Caused by Psychological Stress

Using vowel polygons, exactly their parameters, is chosen as the criterion for achievement of differences between normal state of speaker and relevant speech under real psychological stress. All results were experimentally obtained by created software for vowel polygon analysis applied on ExamStress database. Selected 6 methods based on cross-correlation of different features were classified by the coefficient of variation and for each individual vowel polygon, the efficiency coefficient marking the most significant and uniform differences between stressed and normal speech were calculated. Using the mean of cross- correlation values received for area difference with vector length and angle can be classified as the best method for observing generated differences. Generally, best results for stress detection are achieved by vowel triangles created by /i/-/o/-/u/ and /a/-/i/-/o/ vowel triangles in formant planes containing the fifth formant F5 combined with other formants.

Acoustic tube model of the human vocal tract: formants and vowels

The identity of vowels in speech and singing is determined by the eigenmodes of the human vocal tract (VT); in particular the two lowest modes—which give rise to the so-called formants—are essential. We present a two-tube model to analyse the influence of VT geometry on the formants. It models jaw opening and tongue position in the human VT. The analysis is based on the dispersion relation of plane waves and uses only elementary concepts in physical acoustics. Our model agrees reasonably well with measured data on formants for the centre, [ə], and the corners, [a:], [i:] and [u:], of the vowel triangle. The limitations of the model and the possible extension to a three-tube model are outlined.

Vowel Hyperarticulation in Parrot-, Dog- and Infant-Directed Speech

ABSTRACTVowel triangle area is a phonetic measure of the clarity of vowel articulation. Compared with speech to adults, people hyperarticulate vowels in speech to infants and foreigners but not to pets, despite other similarities in infant- and pet-directed-speech. This suggests that vowel hyperarticulation has a didactic function positively related to the actual, or even the expected, degree of linguistic competence of the audience. Parrots have some degree of linguistic competence yet no studies have examined vowel hyperarticulation in speech to parrots. Here, we compared the speech of 11 adults to another adult, a dog, a parrot, and an infant. A significant linear increase in vowel triangle area was found across the four conditions, showing that the degree of vowel hyperarticulation increased from adult- and dog-directed speech to parrot-directed speech, then to infant-directed speech. This suggests that the degree of vowel hyperarticulation is related to the audience's actual or expected linguistic competence. The results are discussed in terms of the relative roles of speakers' expectations versus listeners' feedback in the production of vowel hyperarticulation; and suggestions for further studies, manipulating speaker expectation and listener feedback, are provided.

Tone and vowel enhancement in Cantonese infant-directed speech at 3, 6, 9, and 12 months of age

Vowel and tone hyperarticulation were investigated in infant-directed speech (IDS) in Cantonese, a tone language. Native Cantonese speaking mothers were recorded speaking to their infants on four occasions, at 3, 6, 9 and 12 months. Unexpectedly, no vowel hyperarticulation in terms of vowel triangle areas or in the dimensions of tongue height or backness (F1 and F2 values) was found in IDS compared to adult-directed speech (ADS). Tone hyperarticulation in IDS, as indexed by the relative area of tone triangles in f0 onset and f0 offset space compared to those in ADS, was found in IDS to infants at all four ages but was reduced somewhat in 12-month-olds. Given that infants’ perceptual attunement to lexical tone begins around 4 months, it appears that parents’ tone hyperarticulation begins before infants have perceptually tuned into native tones and begins to decline by the end of the first year. This provides support for the hypothesis that tone hyperarticulation serves as a bootstrapping mechanism in early language development in tone languages.

Comparison of vowels in maternal speech to adults and to children with hearing loss.

Previous research has indicated that when speaking to normal‐hearing children, maternal caregivers' speech is characterized by a vowel space which is expanded relative to that produced when speaking to other adults. The present study investigated the characteristics of the vowel spaces produced by mothers interacting with hearing‐impaired children who had recently received a cochlear implant (CI), relative to those produced when interacting with another adult. Mothers were recorded interacting with their hearing‐impaired children with CIs in quiet play sessions at 3‐ or 6‐month interval postimplantation as well as in semistructured interviews with another adult. Measurements of F1 and F2 for the vowels /i/, /ɑ/, and /u/ in stressed syllables were taken, and the areas of the resulting vowel triangles for the two production conditions were compared. Preliminary results show that when speaking to their hearing‐impaired children with CIs, vowel spaces of mothers were not expanded relative to when speaking to another adult. The results will be compared with vowel spaces produced to normal‐hearing children and hearing‐impaired children with hearing aids. These findings have implications for developing intervention strategies aimed at caregivers for improving speech and language skills in children with CIs. [Work supported by NIH‐NIDCD R01DC008581.]

Dynamic properties of an acoustic tube: Prediction of vowel systems

Approaches to characterizing and explaining the diverse phonologies of the world’s languages usually begin with data from the analysis of speech signals or from the results of speech production and perception experiments. In the present paper, the dynamic acoustic properties that arise from changing the shape of a simple acoustic tube 18 cm length (without any articulatory machinery) are explored to develop a simple and efficient acoustic communication system. By efficient we mean that minimum deformations of the tube lead to maximum acoustic variations. Intrinsic characteristics of the tube are derived from these specific ‘gestural’ deformations associated with formant trajectories in the acoustic plane. This deductive approach (without reference to data on speech production or speech signals) leads to define an acoustic communication system characterized by its acoustic space and by several specific formant trajectories. The acoustic space fits well with the vowel triangle, and 18 oral vowels can be placed on the trajectories. From these deductive results a tentative explanation of vowel systems is proposed. The good match between deductive prediction and observation results encourages to make further predictions, formulating hypotheses about a unified view of vowel and consonant production, and reconsidering the relation between phonetics and phonology.

Acoustical analysis of timbral modulations on the flute as controlled by phonetic gestures

The purpose of this project is to study the control of timbre on the flute by varying articulatory parameters (i.e. embouchure) which correspond to distinct phonetic gestures. The main goal is to compare the production of a specific timbral modulation on the flute and its vocal reproduction (diphthong) by means of acoustical analyses of these sounds. The recordings of timbral modulations performed on the flute (e.g. by increasing the mouth opening) and reproduced vocally as diphthongs (e.g. [u] ‐> [a] transition) have been analyzed acoustically for intensity as well as for the first two formant trajectories. The results of the formant analyses as presented in an F1‐F2 plane reveal the cardinal vowel triangle and confirm a correlation between the flute timbre modulations and the vocal diphthongs corresponding to the underlying phonetic gestures. In addition, a listening test has shown that flutists are able to perceive and recognize these timbral modulations from the sound alone.

Der Einfluss von Cochlearimplantaten auf die Artikulation von Vokalen

Speech of deaf persons differs considerably from that of speakers with normal hearing. The purpose of this study was to investigate the acoustic changes in articulation of corner vowels in deaf children and adults after cochlear implantation. Thirteen prelingually deaf children and 12 postlingually deaf adults were included in the study. Voice samples of the isolated corner vowels /a/, /i/ and /u/ were analyzed before and 6-12 months after the implantation. The frequencies of the first (F1) and second (F2) formants, the F1/F2 ratio of all three corner vowels, and the area of the vowel triangle were calculated and compared before and 6-12 months after the implantation. In the adults, no significant differences were detected in the formant frequencies, the F1/F2 ratio or the area of the vowel triangle. However, significant change in formant frequencies was detected in the group of 13 prelingually deaf children. After the implantation the F1 of /u/ decreased significantly, and favorable decreases of the F1 of /i/ and the F1/F2 ratio in /i/ and /u/ were close to being statistically significant. All changes caused better phonological difference between the two vowels. The significant change in the F1 of /u/ and the change of F1 of /i/ resulted in the expansion of the vowel space, which was expressed as an increase in the area of the vowel triangle. We suggest that in children the acquired hearing ability and further development of neuromuscular control of articulation are the reasons for the significant improvement after cochlear implantation. The results also suggest that the area of the vowel triangle is a useful and sensitive indicator of the more precise articulation after implantation. In order to achieve better and faster improvement of articulation, regular speech therapy should be included in the rehabilitation of deaf persons after cochlear implantation.

Effects of Intensive Voice Treatment (the Lee Silverman Voice Treatment [LSVT]) on Vowel Articulation in Dysarthric Individuals With Idiopathic Parkinson Disease: Acoustic and Perceptual Findings

To evaluate the effects of intensive voice treatment targeting vocal loudness (the Lee Silverman Voice Treatment [LSVT]) on vowel articulation in dysarthric individuals with idiopathic Parkinson's disease (PD). A group of individuals with PD receiving LSVT (n = 14) was compared to a group of individuals with PD not receiving LSVT (n = 15) and a group of age-matched healthy individuals (n = 14) on the variables vocal sound pressure level (VocSPL); various measures of the first (F1) and second (F2) formants of the vowels /i/, /u/, and /a/; vowel triangle area; and perceptual vowel ratings. The vowels were extracted from the words key, stew, and Bobby embedded in phrases. Perceptual vowel rating was performed by trained raters using a visual analog scale. Only VocSPL, F2 of the vowel /u/ (F2u), and the ratio F2i/F2u significantly differed between patients and healthy individuals pretreatment. These variables, along with perceptual vowel ratings, significantly changed (improved) in the group receiving LSVT only. These results, along with previous findings, add further support to the generalized therapeutic impact of intensive voice treatment on orofacial functions (speech, swallowing, facial expression) and respiratory and laryngeal functions in individuals with PD.