Biomedical subjects

R D Kent

Publications and source records attributed to R D Kent.

18 recordsLinked to original sources

PubMed1992

Acoustic-phonetic contrasts and intelligibility in the dysarthria associated with mixed cerebral palsy.

This study evaluated the relationship between specific acoustic features of speech and perceptual judgments of word intelligibility of adults with cerebral palsy-dysarthria. Use of a contrasting word task allowed for intelligibility analysis and correlated acoustic analysis according to specified spectral and temporal features. Selected phonemic contrasts included syllable-initial voicing; syllable-final voicing; stop-nasal; fricative-affricate; front-back, high-low, and tense-lax vowels. Speech materials included a set of CVC stimulus words. Acoustic data are reported on vowel duration, formant frequency locations, voice onset times, amplitude rise times, and frication durations. Listeners' perceptual assessment of intelligibility of the 16 dysarthric adults by transcription and rating tasks is also presented. All but one acoustic contrast was successfully made as evidenced by measured acoustic differences between contrast pairs. However, the generally successful acoustic contrasts stood in marked contrast to the poorly rated intelligibility scores and high error percentages that were ascribed to the opposite pair members. A second analysis examined the contribution of these acoustic features towards estimates and prediction of intelligibility deficits in speakers with dysarthria. The scaled intelligibility was predicted by multiple regression analysis with 62.6% accuracy by acoustic measures related to one consonant contrast (fricative-affricate) and three vowel contrasts (front-back, high-low, and tense-lax). Other measured contrasts, such as those related to contrast voicing effects and stop-nasal distinctions, did not seem to contribute in a significant way to variability in the intelligibility estimates. These findings are discussed in relation to specific areas of production deficiency that are consistent across different types of dysarthria with cerebral palsy as the etiology.

Adult↗

PubMed1992

Speech analysis systems: an evaluation.

Performance characteristics are reviewed for seven systems marketed for acoustic speech analysis: CSpeech, CSRE, ILS-PC, Kay Elemetrics model 5500 Sona-Graph, MacSpeech Lab II, MSL, and Signalyze. The characteristics reviewed include system components, basic capabilities (signal acquisition, waveform operations, analysis, and other functions), documentation, user interface, data formats and journaling, speed and precision of spectral analysis, and speed and precision of fundamental frequency analysis. Basic capabilities are also tabulated for three recently introduced systems: the Sensimetrics SpeechStation, the Kay Elemetrics Computerized Speech Lab (CSL), and the LSI Speech Workstation. In addition to the capability and performance summaries, this article offers suggestions for continued development of speech analysis systems, particularly in data exchange, journaling, display features, spectral analysis, and fundamental frequency analysis.

Diagnosis, Computer-Assisted↗

PubMed1992

Quantitative description of the dysarthria in women with amyotrophic lateral sclerosis.

Speech intelligibility and its phonetic and acoustic correlates were studied in a group of 10 women with amyotrophic lateral sclerosis (ALS). Intelligibility assessment with a word-identification test indicated that the most disrupted phonetic features pertained to velopharyngeal valving, lingual function for consonant contrasts of place and manner, and syllable shape. An acoustic signature analysis based on trajectories of the first and second formants in selected monosyllabic test words revealed that the mean slope of the second formant (F2) was reduced compared with that of a normal geriatric control group. This F2 slope reduction is interpreted to reflect loss of lingual motoneurons. Acoustic measures of phonatory function for sustained vowel prolongation demonstrated abnormalities in fundamental frequency, perturbations of frequency (jitter) and amplitude (shimmer), and signal-to-noise ratio. The data for women with ALS are compared with data for a normal geriatric control group of women and with data for a group of 25 men with ALS (Kent et al., 1990). Although the overall ranking of errors was similar for males and females with ALS, men were more likely to have impairments of voicing in syllable-initial position.

Adult↗

PubMed1992

Formant trajectory characteristics of males with amyotrophic lateral sclerosis.

The purpose of this study was to describe the formant trajectories produced by males with amyotrophic lateral sclerosis (ALS), a degenerative neuromuscular disease that is typically associated with dysarthria. Formant trajectories of 25 males with ALS and 15 neurologically normal geriatric males were compared for 12 words selected from the speech intelligibility task developed by Kent et al. [J. Speech. Hear. Disord. 54, 482-499 (1989)]. The results indicated that speakers with ALS (1) produced formant transitions having shallower slopes than transitions of normal speakers, (2) tended to produce exaggerations of formant trajectories at the onset of vocalic nuclei, and (3) had greater interspeaker variability of formant transition characteristics than normal speakers. Within the group of ALS speakers, those subjects who were less than 70% intelligible produced distinctly more aberrant trajectory characteristics than subjects who were more than 70% intelligible. ALS subjects who were less than 70% intelligible produced many trajectories that were essentially flat, or that had very shallow slopes. These results are discussed in terms of the speech production deficit in the dysarthria associated with ALS, and with respect to the potential influence of aberrant trajectories on speech intelligibility.

Adult↗

PubMed1991

A theory of neuropsycholinguistic function in stuttering.

A theory of neurolinguistic function is proposed to explain fluency and the production of stuttered and nonstuttered speech disruptions. Central to the theory is the idea that speech involves linguistic and paralinguistic components, each of which is processed by different neural systems that converge on a common output system. Fluent speech requires that these components be integrated in synchrony. When they are dyssynchronous, the result can be either nonstuttered disfluency or stuttering, depending on time pressure. Time pressure is defined as the speaker's need to begin, continue, or accelerate an utterance. Nonstuttered disfluency results when the linguistic and paralinguistic components are dyssynchronous and the speaker is not under time pressure. Stuttering results when the speaker is under time pressure and is relatively unaware of the cause of dyssynchrony. Both of these factors are necessary for the identification of the phenomenon of stuttering. Stuttering is defined as disruption of speech that is experienced by the speaker as a loss of control. The theory presented here accounts for both the disruption and the experienced loss of control.

Biological Evolution↗

PubMed1991

Speech deterioration in amyotrophic lateral sclerosis: a case study.

Few detailed reports have been published on the nature of speech and voice changes during the course of amyotrophic lateral sclerosis (ALS). The subject of this case study is a woman who was diagnosed as having ALS with bulbar signs at the age of 53. Speech intelligibility, pulmonary function, and selected speech and voice functions were tested during an approximately 2-year course of her disease. Over this period, her speech intelligibility, as measured by a multiple-choice word identification test, declined from 98% to 48%. Phonetic features that were most affected during the intelligibility decline included voicing contrast for syllable-initial and syllable-final consonants, place of articulation contrasts for lingual consonants, manner of articulation for lingual consonants, stop versus nasal manner of production, features related to the liquid consonants, and various features related to syllable shape. An acoustic measure, average slope of the second-formant frequency, declined in association with the intelligibility reduction and is thought to reflect the loss of lingual motoneurons. Her pulmonary function also declined over the observation interval, with particularly severe reduction in measures of air flow. Oral diadochokinesis and measures of vocal function (including jitter, shimmer, and signal-to-noise ratio) were highly variable across test sessions. These results are discussed in terms of the challenges they present to sensitive assessment of change and to management of the communication disability in ALS.

Amyotrophic Lateral Sclerosis↗

PubMed1990

Effects of speech rate on the absolute and relative timing of apraxic and conduction aphasic sentence production.

The purpose of this investigation was to provide a constructive replication of the Kent and McNeil (1987, In Phonetic approaches to speech production in aphasia and related disorders. San Diego: College-Hill Press) study of the speech timing characteristics of apraxic and conduction aphasic speakers. Acoustic analysis was used to obtain absolute utterance durations, segment durations, and vowel formant trajectories from utterances produced under control, fast, and slow rate conditions. Segment-to-whole ratios and slope values were calculated. Results support the hypothesis presented by Kent and McNeil (1987) that there is a phonetic-motoric component contributing to the speech patterns of both the apraxic and conduction aphasic speakers sampled. Theories of rate control in normal and disordered speakers are discussed.

Aged↗

PubMed1990

Phonetic variation in multisyllable babbling.

This investigation examined phonetic variation in multisyllable babbling of infants from 0.7 to 0.11. The basis of this investigation was to examine assumptions present in major models of infant vocal development which suggest systematic developmental increases in phonetic variation of these babbles, and posit separate stages of repetitive (multisyllables with non-varied phonetic elements) and non-repetitive (phonetically varied multisyllables) babbling. Eight infants were audiotaperecorded in their homes at ages 0.7, 0.9 and 0.11. The multisyllable vocalizations were categorized based on the presence or absence of phonetic variation, and the source of that variation (place change, manner change or both). Multisyllables were produced with phonetic variation at or near the beginning of multisyllable babbling, which failed to support the existence of distinct stages of repetitive and nonrepetitive babbling.

Humans↗

PubMed1990

Impairment of speech intelligibility in men with amyotrophic lateral sclerosis.

Speech intelligibility was studied in a group of 25 male patients with amyotrophic lateral sclerosis (ALS). The object of the study was to determine the phonetic impairments underlying the speech intelligibility deficits that frequently accompany ALS. Analyses with a word intelligibility test indicated that the most disrupted phonetic features involved phonatory (voicing contrast) function, velopharyngeal valving, place and manner of articulation for lingual consonants, and regulation of tongue height for vowels. The mean error proportion for the five most severely affected features correlated highly (0.97) with the intelligibility score (percent correct). The phonetic feature analyses are one index of bulbar muscle impairment in amyotrophic lateral sclerosis and also may help to direct the speech management in these individuals.

Adult↗

PubMed1990

Speech analysis systems: a survey.

Recently developed, relatively inexpensive systems make digital speech analysis available to many teachers, clinicians, and researchers who have not had access to previous systems. Addressing these prospective users, we survey five microcomputer programs and two dedicated devices for recording, editing, and analyzing speech. We review the capabilities, requirements, and user interface of each system. We recommend considerations for prospective users and for developers of the next generation of such programs and devices. Finally, we briefly survey seven additional systems.

Computers↗

PubMed1979

Isovowel lines for the evaluation of vowel formant structure in speech disorders.

This report describes a system of isovowel lines in the F1-F2 and F2-F3 planes and demonstrates how these linear approximations to vowel formant frequencies for a diverse sample of speakers can be used to evaluate the vowel formant structures of individuals with speech disorders. The application to disordered speech is illustrated with data for dysarthric adults, deaf adolescents, and young children with developmental errors of: Formula: (See Text) production.

Adolescent↗

PubMed1979

Acoustic characteristics of dysarthria associated with cerebellar disease.

The speech of five individuals with cerebellar disease and ataxic dysarthria was studied with acoustic analyses of CVC words, words of varying syllabic structure (stem, stem plus suffix, stem plus two suffixes), simple sentences, the Rainbow Passage, and conversation. The most consistent and marked abnormalities observed in spectrograms were alterations of the normal timing pattern, with prolongation of a variety of segments and a tendency toward equalized syllable durations. Vowel formant structure in the CVC words was judged to be essentially normal except for transitional segments. The greater the severity of the dysarthria, the greater the number of segments lengthened and the degree of lengthening of individual segments. The ataxic subjects were inconsistent in durational adjustments of the stem syllable as the number of syllables in a word was varied and generally made smaller reductions than normal subjects as suffixes were added. Disturbances of syllable timing frequently were accompanied by abnormal contours of fundamental frequency, particularly monotone and syllable-falling patterns. These dysprosodic aspects of ataxic dysarthria are discussed in relation to cerebellar function in motor control.

Aged↗

PubMed1979

Developmental study of vowel formant frequencies in an imitation task.

Imitations of ten synthesized vowels were recorded from 33 speakers including men, women, and children. The first three formant frequencies of the imitations were estimated from spectrograms and considered with respect to developmental patterns in vowel formant structure, uniform scale factors for vowel normalization, and formant variability. Strong linear effects were observed in the group data for imitations of most of the English vowels studied, and straight lines passing through the origin provided a satisfactory fit to linear F1--F2 plots of the English vowel data. Logarithmic transformations of the formant frequencies helped substantially to equalize the dispersion of the group data for different vowels, but formant scale factors were observed to vary somewhat with both formant number and vowel identity. Variability of formant frequency was least for F1 (s.d. of 60 Hz or less for English vowels of adult males) and about equal for F2 and F3 (s.d. of 100 Hz or less for English vowels of adult males).

Adult↗

PubMed1977

Prevention of Salmonella typhimurium infection inpoultry by pretreatment of chickens and poults with intestinal extracts.

Day-old chickens or turkey poults when pretreated with an oral dose of intestinal fluid froma healthy adult bird, were considerably more resistant to the subsequent establishment of Salmonella typhimurium in their intestinal tract than were non-treated chickens or turkey poults. Caecal fluid was more effective as a pretreatment than were washings taken from other parts of the gastro-intestinal tract of a healthy adult bird. This increased resistance of pretreated chickens or poults is thought to result from the rapid establishment of a conventional indigenous microflora which inhabits establishment and growth by the invading enteric pathogen.

Animals↗

PubMed1976

Paroxysmal ataxic dysarthria.

This report reviews 13 cases in which a dysarthria appeared, remitted, and reappeared within seconds. The speech pattern of each case was characteristic of ataxic dysarthria. A cinefluorographic film for one of the subjects provided a rare opportunity to study the articulatory dynamics of this disorder. Multiple sclerosis either was given as a diagnosis or was strongly suspected in each case, and carbamazepine has been an effective treatment. Speculations concerning the origin of the paroxysmal and ataxic character of the dysarthria are presented along with a preliminary checklist for identifying the disorder.

Acoustics↗

PubMed1976

Anatomical and neuromuscular maturation of the speech mechanism: evidence from acoustic studies.

This paper surveys acoustic studies of speech development and discusses the data with respect to the anatomical and neuromuscular maturation of the speech mechanism. The acoustic data on various aspects of speech production indicate that the accuracy of motor control improves with age until adult-like performance is achieved at about 11 or 12 years, somewhat after the age at which speech sound acquisition usually is judged to be complete. Other topics of discussion are (1) problems in the spectrographic analysis of children's speech, (2) formant scale factors that relate children's and adults' data, and (3) identification and diagnosis of developmental disorders through acoustic analyses of speech sounds.

Acoustics↗

PubMed1975

Cineradiographic assessment of articulatory mobility in the dysarthrias.

This paper describes cineradiographic techniques for the assessment of articulatory mobility in dysarthric subjects. Sample data for the mobility ranges of articulatory points on the tongue, lower lip, and jaw are presented for four normal speakers and four dysarthric speakers. In addition, fleshpoint displacements during the articulatory movements of the dysarthric subjects are used to illustrate abnormalities in the range, rate, and direction of speech movements. Discussion of the point-parameterized cineradiographic data emphasizes possibilities for the clinical evaluation of dysarthric impairments.

Cineradiography↗

PubMedDate not supplied

Consonant discrimination as a function of presentation level.

This study examined the effect of presentation level (seven levels ranging from 0 to 60 dB re the subject's SRT) on the discrimination of 20 consonants spoken in CV syllables. The subjects were 10 young adults with normal hearing. It was determined that the performance-intensity functions for individual consonants varied widely. Some sounds were not identified correctly 100% of the time even at the highest level tested, whereas other sounds were consistently identified at 10 dB SL. The data were considered with respect to stimulus and response bias and also were subjected to a feature analysis using features of voice, manner and place.

Adult↗