Characteristics of the lax vowel space in dysarthria.

It has been hypothesized that lax vowels may be relatively unaffected by dysarthria, owing to the reduced vocal tract shapes required for these phonetic events (G. S. Turner, K. Tjaden, & G. Weismer, 1995). It also has been suggested that lax vowels may be especially susceptible to speech mode effects (M. A. Picheny, N. I. Durlach, & L. D. Braida, 1986). Studies evaluating these suggestions are lacking, however. The present study was an initial investigation of the vowel space area formed by the lax vowels /Iota/, /varepsilon/, and /upsilon/, occurring in a passage read in habitual, fast, and slow conditions by speakers with amyotrophic lateral sclerosis (ALS), speakers with Parkinson's disease (PD), and healthy controls. Vowel space areas for speakers with ALS but not speakers with PD differed from those for the appropriate control group. Thus, only the results for the PD group support the hypothesis that lax vowel space areas for speakers with dysarthria should be similar to those for neurologically normal talkers. Compared with the habitual condition, rate reduction was associated with an expanded vowel space area for all of the healthy talkers but for only about half of the speakers with dysarthria. In addition, about half of the speakers in each group demonstrated a reduced vowel space area for the fast condition relative to the habitual condition, although the statistical analyses indicated no difference in vowel space areas for the fast and habitual conditions. The current study therefore provides only limited support for the idea that lax vowels are highly susceptible to speech mode effects, at least when the speech modes under consideration include faster-than-normal and slower-than normal rates. Clinical implications are discussed.     

Articulatory movements during vowels in speakers with dysarthria and healthy controls.

PURPOSE: This study compared movement characteristics of markers attached to the jaw, lower lip, tongue blade, and dorsum during production of selected English vowels by normal speakers and speakers with dysarthria due to amyotrophic lateral sclerosis (ALS) or Parkinson disease (PD). The study asked the following questions: (a) Are movement measures different for healthy controls and speakers with ALS or PD, and (b) Are articulatory profiles comparable for speakers with ALS and speakers with PD? METHOD: Nineteen healthy controls and 15 speakers with dysarthria participated in this study. The severity of dysarthria varied across individuals and between the 2 disorder groups. The stimuli were 10 words (i.e., seed, feed, big, dish, too, shoo, bad, cat, box, and dog) embedded into sentences read at a comfortable reading rate. Movement data were collected using the X-ray microbeam. Movement measures included distances, durations, and average speeds of vowel-related movement strokes. RESULTS: Differences were found (a) between speakers with ALS and healthy controls and (b) between speakers with ALS and PD, particularly in movement speed. Tongue movements in PD and ALS were more consistently different from healthy controls than jaw and lower lip movements. This study showed that the effects of neurologic disease on vowel production are often articulator-, vowel-, and context-specific. CONCLUSIONS: Differences in severity between the speakers with PD and ALS may have accounted for some of the differences in movement characteristics between the groups. These factors need to be carefully considered when describing the nature of speech disorder and developing empirically based evaluation and treatment strategies for dysarthria.     

Vowel space characteristics and vowel identification accuracy.

PURPOSE: To examine the relation between vowel production characteristics and intelligibility. METHOD: Acoustic characteristics of 10 vowels produced by 45 men and 48 women from the J. M. Hillenbrand, L. A. Getty, M. J. Clark, and K. Wheeler (1995) study were examined and compared with identification accuracy. Global (mean f0, F1, and F2; duration; and amount of formant movement) and fine-grained measures (vowel space area; mean distance among vowels; f0, F1, and F2 ranges; duration ratio between long and short vowels; and formant movement ratio between dynamic and static vowels) were used to predict identification scores. Acoustic measures of the most frequently confused pairs (/ae/-/epsilon/ and /a/-/inverted v/) were compared. RESULTS: Global and fine-grained measures accounted for less than 1/4 of variance in identification scores: Vowel space area alone accounted for 9%-12% of variance. Differences in vowel identification were largely due to poor identification of /ae/, /epsilon/, /a/, or /inverted v/. Well-identified vowels were distinctive in formant frequencies, duration, and amount of formant movement over time. CONCLUSIONS: Distinctiveness among neighboring vowels is more important in determining vowel intelligibility than vowel space area. Acoustic comparison of confused vowels may be more useful in studying intelligibility of normal and disordered speech than in measuring vowel space area.     

Rate and loudness manipulations in dysarthria: acoustic and perceptual findings.

Both rate reduction and increased loudness reportedly are associated with an increase in the size of the articulatory-acoustic working space and improved acoustic distinctiveness for speakers with dysarthria. Improved intelligibility also has been reported. Few studies have directly compared rate and loudness effects for speakers with dysarthria, however, although rate reduction and increasing vocal loudness are common treatment techniques. In the current study, 15 speakers with dysarthria secondary to multiple sclerosis, 12 speakers with dysarthria secondary to Parkinson's disease (PD), and 15 healthy controls read a passage in habitual, loud, and slow conditions. Rate and loudness variations were elicited using magnitude production. Acoustic measures included articulatory rate, sound pressure level, vowel space area, first moment difference measures, and F2 trajectory characteristics for diphthongs. Ten listeners scaled intelligibility for reading passages produced by the speakers with dysarthria. Relationships between intelligibility estimates and acoustic measures were determined by regression analysis. All speaker groups reduced articulatory rate for the slow condition and increased vocal intensity for the loud condition, relative to the habitual condition. Vowel acoustic distinctiveness, as indexed by vowel space area, was maximized in the slow condition, but stop consonant acoustic distinctiveness, as indexed by first moment difference measures, was maximized in the loud condition. F2 slope measures for diphthongs were not consistently affected by rate or loudness. Scaled intelligibility for speakers with PD also improved in the loud condition relative to both the habitual and slow conditions. Intelligibility estimates for speakers with dysarthria, however, were not strongly related to acoustic measures of supraglottal behavior. Findings are compared with previous studies, and hypotheses for future treatment studies are discussed.     

Interarticulator coordination in dysarthria: an X-ray microbeam study.

Articulatory discoordination is often said to be an important feature of the speech production disorder in dysarthria, but little experimental work has been done to identify and specify the coordination difficulties. The present study evaluated the coordination of labial and lingual gestures for /u/ production in persons with Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and in control participants. Both tongue backing/raising and reduction of the area enclosed by the lips can produce the characteristic low F2 of /u/. The timing of these articulatory gestures with respect to the acoustic target of a low F2 was inferred from X-ray microbeam data. Pellet motions of the tongue dorsum and lips revealed the timing of the lingual and labial gestures to be strongly linked together (synchronized), predictive of the temporal location of the lowest F2 within the vocalic nucleus, and scaled proportionately to the overall vowel duration in control participants. Somewhat surprisingly, essentially the same findings were obtained in the speakers with dysarthria. These relationships were noisier among the speakers with dysarthria, but the global synchronization patterns applied to all 3 groups. Further analyses revealed the synchronization to be less well defined and more variable across speakers with ALS, as compared to speakers with PD and the controls. Results are discussed relative to concepts of coordination in dysarthria.     

极重度听障儿童单元音共振峰测量及分析

目的 探讨3～6岁极重度听障儿童单元音共振峰的平均值与健听儿童的差异,为指导听障儿童的语言康复训练提供参考.方法 使用语音工作站采样分析,让10名3～6岁的极重度听障儿童在自然舒适状态下发/a/、/o/、/e/、/i/、/u/、/ü/6个元音,每个音持续3 s以上,并截取各声样中的3 s平稳段进行声学参数的检测和分析.同时,与同年龄段健听儿童的数据做对照.结果 听障组6个单元音的3个共振峰与健听组相比较,所有元音的F1无显著性差异(P＞0.05);元音/o/和/u/的F2无显著性差异(P＞0.05),其余各元音的F2有显著性差异(P＜0.05);所有元音的F3都有显著性差异(P＜0.05).结论 极重度听障儿童的单元音共振峰与健听儿童有差异,这可能是引起听障儿童发这些元音不清楚的原因之一.     

Perception of coarticulatory information in normal speech and dysarthria.

PURPOSE: This study addressed three research questions: (a) Can listeners use anticipatory vowel information in prevocalic consonants produced by talkers with dysarthria to identify the upcoming vowel? (b) Are listeners sensitive to interspeaker variation in anticipatory coarticulation during prevocalic consonants produced by healthy talkers and/or talkers with dysarthria, as measured by vowel identification accuracy? (c) Is interspeaker variation in anticipatory coarticulation reflected in measures of intelligibility? METHOD: Stimuli included 106 CVC words produced by 20 speakers with either Parkinson's disease or multiple sclerosis or by 16 healthy controls characterized by an operationally defined normal, under, or over level of anticipatory vowel coarticulation. Ten listeners were presented with prevocalic consonants for identification of the vowel. Ten additional listeners judged single-word intelligibility. An analysis of variance was used to determine differences in vowel identification accuracy and intelligibility as a function of speaker group, coarticulation level, and vowel type. RESULTS: Listeners accurately identified vowels produced by all speaker groups from the aperiodic portion of prevocalic consonants, but interspeaker variations in strength of coarticulation did not strongly affect vowel identification accuracy or intelligibility. CONCLUSIONS: Listeners appear to be tuned to similar types of information in the acoustic speech stream irrespective of the source or speaker, and any perceptual effects of interspeaker variation in coarticulation are subtle.     

Comparación de la producción vocal en niños con hipoacusia prelocutiva con adaptación audioprotésica e implante coclear con normooyentes

Introduction and objectivesInadequate auditory feedback in prelingually deaf children alters the articulation of consonants and vowels.The purpose of this investigation was to compare vowel production in Spanish-speaking deaf children with cochlear implantation, and with hearing-aids with normal-hearing children by means of acoustic analysis of formant frequencies and vowel space.MethodsA total of 56 prelingually deaf children (25 with cochlear implants and 31 wearing hearing-aids) and 47 normal-hearing children participated. The first 2 formants (F1 and F2) of the five Spanish vowels were measured using Praat software. One-way analysis of variance (ANOVA) and post hoc Scheffé test were applied to analyze the differences between the 3 groups. The surface area of the vowel space was also calculated.ResultsThe mean value of F1 in all vowels was not significantly different between the 3 groups. For vowels /i/, /o/ and /u/, the mean value of F2 was significantly different between the 2 groups of deaf children and their normal-hearing peers.ConclusionBoth prelingually hearing-impaired groups tended toward subtle deviations in the articulation of vowels that could be analyzed using an objective acoustic analysis programme.     

Acoustic and perceptual consequences of articulatory rate change in Parkinson disease.

This study sought to characterize the relationship among voluntary rate modification, vocal tract acoustic output, and perceptual impressions of speech for individuals with idiopathic Parkinson disease (PD). Healthy control speakers were studied for comparison purposes. Four research questions were addressed: (1) How is rate modification evidenced in acoustic measures of segmental and global timing? (2) What is the impact of rate modification on measures of acoustic working space for select vowels and consonants? (3) What is the impact of rate modification on perceptual impressions of severity? (4) Are rate-induced changes in measures of acoustic working space related to perceptual impressions of severity? Speakers read the Farm Passage at habitual, slow, and fast rates. The vowels /i/, /ae/, /u/, and /A/ and the fricatives /s/ and /S/ were of interest. Acoustic measures included articulatory rate, segment durations, vowel formant frequencies, and first moment coefficients. Measures of acoustic working space for vowels and fricatives also were derived. The results indicated that temporal acoustic measures changed in the expected direction across rate conditions, with a tendency toward slightly faster rates for the PD group. In addition, the relative rate change for the Fast and Slow conditions compared to the Habitual condition was similar across groups. Rate did not strongly affect measures of acoustic working space for the PD group as a whole, but there was a tendency for slower rates to be associated with larger measures of acoustic working space. Finally, there was not a strong relationship between perceived severity and measures of acoustic working space across the rate continuum for either group. Rather, the relationship between perceived severity and measures of acoustic working space was such that the PD group exhibited smaller measures of acoustic working space and more severe perceptual estimates than the control speakers, irrespective of rate condition.     

Articulatory changes in muscle tension dysphonia: Evidence of vowel space expansion following manual circumlaryngeal therapy

In a preliminary study, we documented significant changes in formant transitions associated with successful manual circumlaryngeal treatment (MCT) of muscle tension dysphonia (MTD), suggesting improvement in speech articulation. The present study explores further the effects of MTD on vowel articulation by means of additional vowel acoustic measures. Pre- and post-treatment audio recordings of 111 women with MTD were analyzed acoustically using two measures: vowel space area (VSA) and vowel articulation index (VAI), constructed using the first (F1) and second (F2) formants of 4 point vowels/ ɑ, i, æ, u/, extracted from eight words within a standard reading passage. Pairwise t-tests revealed significant increases in both VSA and VAI, confirming that successful treatment of MTD is associated with vowel space expansion. Although MTD is considered a voice disorder, its treatment with MCT appears to positively affect vocal tract dynamics. While the precise mechanism underlying vowel space expansion remains unknown, improvements may be related to lowering of the larynx, expanding oropharyngeal space, and improving articulatory movements.Learning outcomes: The reader will be able to: (1) describe possible articulatory changes associated with successful treatment of muscle tension dysphonia; (2) describe two acoustic methods to assess vowel centralization and decentralization, and; (3) understand the basis for viewing muscle tension dysphonia as a disorder not solely confined to the larynx.     

Effects of tonsillectomy and/or adenoidectomy on vocal function: laryngeal, supralaryngeal and perceptual characteristics

A prospective, non-randomized study evaluated the effects of tonsillectomy and/or adenoidectomy (T +/- A) on acoustic and perceptual aspects of vocal function. Thirty-one children, ranging in age from 4 to 15 years participated and measurements were made prior to and 3 months following surgery. Twenty-three children had T +/- A and eight had adenoidectomy alone. Quantitative acoustic measures included: laryngeal (vocal fundamental frequency, FO) and supralaryngeal characteristics of sustained vowels (F1 and F2 formants, formant bandwidths, two-dimensional measures of vowel space) and temporal properties of consonant-vowel productions (diadochokinetic syllable rates). Perceptual measures were based on samples of continuous speech, using the Buffalo voice profile (BVP) and parental interviews/questionnaires were used to evaluate other aspects of surgery (i.e. subjective speech changes, protracted pain, difficulty swallowing, bleeding, etc.). Based on ANOVA, no significant post-surgical changes were detected for the majority of acoustic speech measures studied (vocal F0, formant bandwidths, measures of vowel space or diadochokinetic rates). However, the F2 formant frequency for vowels /i/ and /a/ increased and F1 decreased for /o/ following surgery. These changes had the largest effect on the structure of vowel /i/, which became more acute and diffuse following surgery. Furthermore, of the majority of perceptual measured studied with the BVP, 92% showed no change postoperatively. However, in the category of resonance, a significant decrease in hyponasality was detected. These results demonstrate that removing soft tissue from the oropharynx has only minimal impact on quantitative or qualitative (perceptual) aspects of vocal function, when measurements are made approximately 15 weeks post surgery.     

无喉者发不同元音时的声学参数及气管内压力比较

目的　比较无喉者发不同元音时的声学参数及气管内压的异同。方法　检测了 2 4例喉全切除气管断端膜样部食管吻合分流发声重建术后患者和 16例喉全切除术后食管音患者分别发元音 a 和 i 时的声学参数 ,测定了 2 0例发声重建术后患者分别发 a 和 i 时的气管内压 ,并进行统计学分析。结果　两组无喉患者发不同元音 a 和 i 时 ,其声学参数无显著性差异 (P >0 .0 5 ) ,发声重建术后患者的气管内压发 i 音时较发 a 音时高 ,有显著性差异 (P <0 .0 5 )。结论　应用元音 a 和 i 在评价无喉者发声的声学参数有一致的临床意义 ;而发声重建术后患者在发不同元音时 ,气管内压值不同     

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.

PURPOSE: 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). METHOD: 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. RESULTS: 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. CONCLUSION: 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.     

Phonological space in the speech of the hearing impaired

The vowels /a/, /i/, and /u/ form the extreme points of vowel triangle in Kannada language. First and second formant frequencies of these vowels were measured to determine the phonological space in the speech of the 30 deaf subjects and 30 normally hearing subjects. The phonological space was found to be reduced in the speech of the hearing-impaired subjects, and the reduction was primarily due to the lowering of the second formant of the vowel /i/. Therapeutic implications have been drawn.     

Language-specific, hearing-related changes in vowel spaces: a preliminary study of English- and Spanish-speaking cochlear implant users.

OBJECTIVE: This study investigates the role of hearing in vowel productions of postlingually deafened cochlear implant users. Two hypotheses are tested that derive from the view that vowel production is influenced by competing demands of intelligibility for the listener and least effort in the speaker: 1) Hearing enables a cochlear implant user to produce vowels distinctly from one another; without hearing, the speaker may give more weight to economy of effort, leading to reduced vowel separation. 2) Speakers may need to produce vowels more distinctly from one another in a language with a relatively "crowded" vowel space, such as American English, than in a language with relatively few vowels, such as Spanish. Thus, when switching between hearing and non-hearing states, English speakers may show a tradeoff between vowel distinctiveness and least effort, whereas Spanish speakers may not. DESIGN: To test the prediction that there will be a reduction of average vowel spacing (AVS) (average intervowel distance in the F1-F2 plane) with interrupted hearing for English-speaking cochlear implant users, but no systematic change in AVS for Spanish cochlear implant users, vowel productions of seven English-speaking and seven Spanish-speaking cochlear implant users, who had been using their implants for at least 1 yr, were recorded when their implant speech processors were turned off and on several times in two sessions. RESULTS: AVS was consistently larger for the English speakers with hearing than without hearing. The magnitude and direction of AVS change was more variable for the Spanish speakers, both within and between subjects. CONCLUSION: Vowel distinctiveness was enhanced with the provision of some hearing in the language group with a more crowded vowel space but not in the language group with fewer vowels. The view that speakers seek to minimize effort while maintaining the distinctiveness of acoustic goals receives some support.     

Formant-frequency differences between isolated whispered and phonated vowel samples produced by adult female subjects

This study was designed to investigate the formant frequencies of phonated and whispered productions of five test vowels (/i/, /u/, /ae/, /a/). Each test vowel was sustained twice in isolation--once phonated, one whispered--by 20 adult female subjects. The phoneme represented by each recorded production was identified independently by 11 listeners. Only those samples identified by 6 or more of the listeners as the vowel intended were retained for a further (acoustic) analysis. An acoustic spectrum of each retained sample was obtained to permit formant measurements. To provide the clearest formant delineation possible in our lab, the phonated samples were analyzed by broadband spectrography and the whispered samples by very narrow-band spectrography. This report presents the formant frequencies (F1-F3) of the test productions as measured from the acoustic vowel spectra and the formant-frequency differences between the phonated and whispered productions. In general, the results showed a trend for whispered vowel formants to be higher in frequency than phonated vowel formants, but that trend was only strongly evident for F1.     

Talker differences in clear and conversational speech: acoustic characteristics of vowels.

PURPOSE: To determine the specific acoustic changes that underlie improved vowel intelligibility in clear speech. METHOD: Seven acoustic metrics were measured for conversational and clear vowels produced by 12 talkers-6 who previously were found (S. H. Ferguson, 2004) to produce a large clear speech vowel intelligibility effect for listeners with normal hearing identifying vowels in background noise (the big benefit talkers), and 6 who produced no clear speech vowel intelligibility benefit (the no benefit talkers). RESULTS: For vowel duration and for certain measures of the overall acoustic vowel space, the change from conversational to clear speech was significantly greater for big benefit talkers than for no benefit talkers. For measures of formant dynamics, in contrast, the clear speech effect was similar for the 2 groups. CONCLUSION: These results suggest that acoustic vowel space expansion and large vowel duration increases improve vowel intelligibility. In contrast, changing the dynamic characteristics of vowels seems not to contribute to improved clear speech vowel intelligibility. However, talker variability suggested that improved vowel intelligibility can be achieved using a variety of clear speech strategies, including some apparently not measured here.     

Acoustical analysis of Spanish vowels produced by laryngectomized subjects.

The purpose of this study was to describe the acoustic characteristics of Spanish vowels in subjects who had undergone a total laryngectomy and to compare the results with those obtained in a control group of subjects who spoke normally. Our results are discussed in relation to those obtained in previous studies with English-speaking laryngectomized patients. The comparison between English and Spanish, which diFfer widely in the size of their vowel inventories, will help us to determine specific or universal vowel production characteristics in these patients. Our second objective was to relate the acoustic properties of these vowels to the perceptual data obtained in our previous work (J. L. Miralles & T. Cervera, 1995). In that study, results indicated that vowels produced by alaryngeal speakers were well perceived in word context. Vowels were produced in CVCV word context by two groups of patients who had undergone laryngectomy: tracheoesophageal speakers (TES) and esophageal speakers. In addition a control group of normal talkers was included. Audio recordings of 24 Spanish words produced by each speaker were analyzed using CSL (Kay Elemetrics). Results showed that F1, F2, and vowel duration of alaryngeal speakers differ significantly from normal values. In general, laryngectomized patients produce vowels with higher formant frequencies and longer durations than the group of laryngeal subjects. Thus, the data indicate modifications either in the frequency or temporal domain, following the same tendency found in previous studies with English-speaking laryngectomized speakers.     

The effect of phonological neighborhood density on vowel articulation.

Recent literature suggests that phonological neighborhood density and word frequency can affect speech production, in addition to the well-documented effects that they have on speech perception. This article describes 2 experiments that examined how phonological neighborhood density influences the durations and formant frequencies of adults' productions of vowels in real words. In Experiment 1, 10 normal speakers produced words that covaried in phonological neighborhood density and word frequency. Infrequent words with many phonological neighbors were produced with shorter durations and more expanded vowel spaces than frequent words with few phonological neighbors. Results of this experiment confirmed that this effect was not related to the duration of the vowels constituting the high- and low-density words. In Experiment 2, 15 adults produced words that varied in both word frequency and neighborhood density. Neighborhood density affected vowel articulation in both high- and low-frequency words. Moreover, frequent words were produced with more contracted vowel spaces than infrequent words. There was no interaction between these factors, and the vowel duration did not vary as a function of neighborhood density. Taken together, the results suggest that neighborhood density affects vowel production independent of word frequency and vowel duration.