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Biomedical subjects

R D Kent

Publications and source records attributed to R D Kent.

At least 19 recordsLinked to original sources
PubMed1998

DECTalk and MacinTalk speech synthesizers: intelligibility differences for three listener groups.

This study examined word level intelligibility differences between DECTalk and MacinTalk speech synthesizers using the Modified Rhyme Test in an open format transcription task. Three groups of listeners participated: inexperienced, speech-language pathologists, and speech synthesis experts. Results for between-subjects ANOVA showed that the expert group correctly identified a significantly higher number of words than each of the other listener groups. For the within-subjects factor of voice, simple effects ANOVA and post hoc contrasts within each group showed that listeners had higher intelligibility scores for the DECTalk male voice, Perfect Paul, than for the MacinTalk male voice, Bruce. No other pairwise gender/age-matched differences were found between the two synthesizers.

Adult↗
PubMed1997

A speaking task analysis of the dysarthria in cerebellar disease.

Cerebellar disease affects a number of skilled movements, including those in speech. Ataxic dysarthria, the speech disorder that typically accompanies cerebellar disease, was studied by acoustic methods. Control subjects and subjects with ataxic dysarthria were recorded while performing a number of speaking tasks, including sustained vowel phonation, syllable repetition, monosyllabic word production (intelligibility test), sentence recitation, and conversation. Acoustic data derived from the speech samples confirmed the hypothesis that temporal dysregulation is a primary component of the speech disorder. The data also show that the nature of the disorder varies with the speaking task. This result agrees with observations on other motor systems in subjects with cerebellar disease and may be evidence of a dissociation of impairments. Suggestions are offered on the selection of measures for a given task and on the role of the cerebellum in the regulation of speaking.

Adult↗
PubMed1993

Vocal tract acoustics.

This paper considers the topic of vocal tract acoustics from the three perspectives: (a) the acoustic theory of speech production; (b) contemporary laboratory methods for acoustic analysis, and (c) measurement of the acoustic signal of speech. Linear source-filter theory is the standard acoustic theory of speech production and is the foundation for remarkable advances in the analysis and synthesis of speech. Digital signal processing, the dominant laboratory method for speech analysis, enables the acquisition and recording of the acoustic speech signal but also implements quantitative algorithms largely based on linear source-filter theory. Measurements of the acoustic signal reflect the acoustic theory of speech production, laboratory methods for signal analysis, and principles of experimental phonetics. Basic issues in the three domains of theory, laboratory methods, and measurement are summarized as they pertain to the interests of the voice scientist, voice clinician, and voice teacher.

Female↗
PubMed1993

Speaking rate and speech movement velocity profiles.

The effects of speaking rate on the velocity profiles of movements of the lower lip and tongue tip during the production of stop consonants were examined using an x-ray microbeam system. Five young adults used a magnitude production task to produce five speaking rates that ranged from very fast to very slow. Results indicated that changes in speaking rate were associated with changes in the topology of the speech movement velocity-time function. Specifically, the velocity profile changed from a symmetrical, single-peaked function at the fast speaking rates to an asymmetrical and multi-peaked function at the slow speaking rates. This variation in velocity profile shape is interpreted as support for the view that alterations in speaking rate are associated with changes in motor control strategies. In particular, the control strategy for speech gestures produced at fast speaking rates appears to involve unitary movements that may be predominantly preprogrammed, whereas gestures produced at slow speaking rates consist of multiple submovements that may be influenced by feedback mechanisms.

Adult↗
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↗
PubMed1989

Toward phonetic intelligibility testing in dysarthria.

The measurement of intelligibility in dysarthric individuals is a major concern in clinical assessment and management and in research on dysarthria. The measurement objective is complicated by the fact that intelligibility is not an absolute quantity but rather a relative quantity that depends on variables such as test material, personnel, training, test procedures, and state of the speaker. This paper reviews scaling procedures and item identification tests as they have been applied to dysarthric speech. Based in part on previous studies of speech of the hearing impaired, a profile has been designed to direct research on the acoustic or physiologic correlates of dysarthric intelligibility impairment. In addition, a word intelligibility test is proposed for use with dysarthric speakers. This test is designed to examine 19 acoustic-phonetic contrasts that are likely to (a) be sensitive to dysarthric impairment and (b) contribute significantly to speech intelligibility. Preliminary data from a sample of subjects with amyotrophic lateral sclerosis are presented to illustrate the use of this test in the phonetic interpretation of intelligibility impairment.

Adult↗
PubMed1988

The acoustic signature for intelligibility test words.

As part of a research program that aims to develop an explicit acoustic basis for a single-word intelligibility test, an initial attempt to characterize the formant trajectories and segment durations of seven test words produced by 30 normal speakers is described. These characterizations are referred to as "acoustic signatures." The data indicate that: (1) formant trajectories show two sex effects, namely, that females are more variable as a group than males and tend to have greater slopes for the transitional segment of the second-formant trajectories and that these effects are consistent across words; (2) Bark transformations of the frequency data do not seem to eliminate the interspeaker differences in formant trajectories, nor do they eliminate either of the sex effects described above; and (3) segment durations have different variabilities depending on the syllabic structure of the word; no sex effect was noted here. The discussion focuses on the appropriate form for the acoustic signatures, as well as factors that should be considered in selecting words for signature development. To demonstrate the potential application of these data, formant trajectory and segment duration data from 18 speakers with amyotrophic lateral sclerosis and varying degrees of dysarthria are compared to the acoustic signature for the word wax.

Aged↗