Onset of voicing in stuttered and fluent utterances

Electroglottographic (EGG) and acoustic waveforms of the first few glottal pulses of voicing were monitored and voice onset time (VOT) measured during an adaptation task performed by stutterers and controls. The fluent utterances of stutterers resembled those of control subjects. After dysfluencies, however, the EGG signal increased gradually, lending physiological support to the technique of "easy onset" of voicing. EGG waveforms also served to help differentiate mild from severe stutterers. Idiosyncratic ritualized laryngeal behavior, sometimes including physiological tremor, was evident in the EGG record.     

The relationship of stuttering severity and treatment length to temporal measures of stutterers' perceptually fluent speech

The purpose of this study was to investigate the relationship between stuttering severity and treatment length to temporal measures of stutterers' perceptually fluent speech. Seventeen adult stutterers (4 mild, 8 moderate, and 5 severe) were divided into two treatment categories. One group with limited exposure to treatment (n = 7) consisted of stutterers who had completed 0-10 hr of treatment. Another group with an extensive period of treatment (n = 10) consisted of stutterers who had completed 47-212 hr of treatment. All subjects were asked to repeat a simple phrase and read a prose passage. Spectrographic measures of the stutterers' voice onset times, vowel, consonant, and phrase durations were obtained from perceptibly fluent productions of the isolated phrase and from a phrase extracted from the oral reading. Results showed that there were no significant differences among stuttering severity groups or the two groups with different lengths of treatment. These results suggest that changes in temporal measures of stutterers' fluency might occur through the process of treatment, but those changes are not related to stuttering severity or length of treatment.     

Formant frequencies of stuttered and fluent vowels

The formant frequencies of 15 adult stutterers' fluent and disfluent vowels and the formant frequencies of stutterers' and nonstutterers' fluent vowels were compared in an F1-F2 vowel space and in a normalized F1-F2 vowel space. The results indicated that differences in formant frequencies observed between the stutterers' and nonstutterers' vowels can be accounted for by differences among the vocal tract dimensions of the talkers. In addition, no differences were found between the formant frequencies of the fluent and disfluent vowels produced by the stutterers. The overall pattern of these results indicates that, contrary to recent reports (Klich & May, 1982), stutterers do not exhibit significantly greater vowel centralization than nonstutterers.     

Acoustic analysis of stutterers' fluent speech before and after therapy

The speech of 14 stutterers was analyzed prior to and at the termination of a 5-week stuttering therapy program to examine the relationship between nine selected acoustic variables and stuttering frequency. Group analyses indicated that pre- to post-therapy changes in stuttering frequency were accompanied by mean changes in five of the nine acoustic variables, a finding which is consistent with previous literature. Correlational analyses indicated that only silence in the voiced stop consonant intervocalic interval (IVI) was significantly correlated with stuttering frequency prior to therapy (i.e., lower stuttering frequency values were associated with shorter durations of silence during the IVI). Furthermore, the degree of reduction in silence was positively correlated with the magnitude of reduction in stuttering frequency due to therapy. These findings suggest that silence in the IVI may reflect the operational status of some mechanism which may underlie disfluent speech.     

Differences of articulation rate and utterance length in fluent and disfluent utterances of preschool children who stutter

Purpose

The purpose of this study was to investigate characteristics of four types of utterances in preschool children who stutter: perceptually fluent, containing normal disfluencies (OD utterance), containing stuttering-like disfluencies (SLD utterance), and containing both normal and stuttering-like disfluencies (SLD + OD utterance). Articulation rate and length of utterance were measured to seek the differences. Because articulation rate may reflect temporal aspects of speech motor control, it was predicted that the articulation rate would be different between perceptually fluent utterances and utterances containing disfluencies. The length of utterance was also expected to show different patterns.

Method

Participants were 14 preschool children who stutter. Disfluencies were identified from their spontaneous speech samples, and articulation rate in syllables per second and utterance length in syllables were measured for the four types of utterances.

Results and discussion

There was no significant difference in articulation rate between each type of utterance. Significantly longer utterances were found only in SLD + OD utterances compared to fluent utterances, suggesting that utterance length may be related to efforts in executing motor as well as linguistic planning. The SLD utterance revealed a significant negative correlation in that longer utterances tended to be slower in articulation rates. Longer utterances may place more demand on speech motor control due to more linguistic and/or grammatical features, resulting in stuttering-like disfluencies and a decreased rate.

Learning outcomes

The reader will learn about and be able to: (a) distinguish the difference between measures of overall speaking rate and articulation rate; (b) explain the theoretical and clinical trends of articulation rate in stuttering; (c) discuss how utterances containing stuttering-like disfluencies, utterances containing other disfluencies, and utterances containing both stuttering-like disfluencies and other disfluencies influence articulation rate; and (d) discuss how the length of utterances is related to disfluencies.     

Coordination of aerodynamic and phonatory processes in fluent speech utterances of stutterers

It has often been suggested that there is a close relation between problems in the coordination of respiratory, phonatory, and articulatory processes and dysfluencies in speech production. However, empirical support for this hypothesis is scarce, because most studies of speech behavior have been restricted to a single motor process. The present investigation examines the interactions of respiration (specifically the build up of subglottal pressure), phonation, and articulation. Pressure build-up patterns preceding the onset of phonation were studied in 573 fluent utterances of 10 stutterers and in 552 utterances of 7 control subjects. Stutterers evidenced deviant patterns of subglottal pressure build-up much more often than did control speakers. Electroglottographic records of voice onset were classified as either abrupt or gentle and with respect to the presence or absence of gross irregularities in amplitude (shimmer) and period duration (jitter). Stutterers evidenced abrupt voice onsets significantly more often than did controls. The occurrence of jitter and shimmer, however, did not differ significantly across the groups. Acoustic measures of abruptness of voice onset, first syllable duration, and average syllable duration were also obtained, but they failed to differ significantly between the two groups. This study corroborates previous findings that perceptually fluent utterances of stutterers may differ, on a physiological level, from the speech of nonstutterers.     

Preparation time and response complexity effects on stutterers' and nonstutterers' acoustic LRT

Nonstutterers', mild stutterers', and severe stutterers' acoustic laryngeal reaction times (LRTs) were recorded for isolated vowels and nonpropositional VCV responses in different stimulus conditions governing response preparation. In all stimulus-response conditions severe stutterers produced the longest LRTs, followed in turn by mild stutterers and nonstutterers. The three groups significantly differed from one another in most conditions, but the magnitude of difference between mild and severe stutterers was notably greater than the difference between mild stutterers and nonstutterers. LRT changes as a function of stimulus condition showed that, in general, nonstutterers were best able to use a preparation-facilitating stimulus condition to reduce LRT, and severe stutterers least able to do so. LRT changes as a function of response complexity showed that only nonstutterers produced statistically significant within-group differences. Patterns of LRT change as a combined function of group, stimulus condition, and response type suggest a complex relationship between stutterer severity, preparation time, and type of response complexity. Results illustrate aspects of Goldberg's (1985) model of preparation processes, and support hypotheses that stutterer subgroups show differential preparation deficits along with high motor initiation variability.     

Influences of length and syntactic complexity on the speech motor stability of the fluent speech of adults who stutter.

The purpose of the present study was to investigate the impact of utterance length and syntactic complexity on the speech motor stability of adults who stutter. Lower lip movement was recorded from 8 adults who stutter and 8 normally fluent controls. They produced a target phrase in isolation (baseline condition) and the same phrase embedded in utterances of increased length and/or increased syntactic complexity. The spatiotemporal index (STI) was used to quantify the stability of lower lip movements across multiple repetitions of the target phrase. Results indicated: (a) Adults who stutter demonstrated higher overall STI values than normally fluent adults across all experimental conditions, indicating decreased speech motor stability; (b) the speech motor stability of normally fluent adults was not affected by increasing syntactic complexity, but the speech motor stability of adults who stutter decreased when the stimuli were more complex; (c) increasing the length of the target utterance (without increasing syntactic complexity) did not affect the speech motor stability of either speaker group. These results indicate that language formulation processes may affect speech production processes and that the speech motor systems of adults who stutter may be especially susceptible to the linguistic demands required to produce a more complex utterance. The present findings, therefore, support the hypothesis that linguistic complexity is one factor that contributes to the disruptions of speech motor stability characteristic of stuttering.     

A comparison of stutterers' and nonstutterers' affective, cognitive, and behavioral self-reports

This study compared stutterers' and nonstutterers' communication attitudes. A self-report inventory based on a tripartite attitudinal model was administered to 75 adult stutterers and 81 adult nonstutterers. Ratings of 39 items representing 13 situational subscales, or types of speaking situations, on four response scales reflecting behavioral, affective, and cognitive components and a frequency scale were obtained. Self-ratings of speech enjoyment and speech skills best discriminated stutterers and nonstutterers. However, these self-ratings were related for both stutterers and nonstutterers. Frequency of encountering speaking situations was related to enjoyment of speech for stutterers, but not for nonstutterers. Moreover, stutterers, unlike nonstutterers, believed that most people's enjoyment of speech was not related to most people's speech skills. Similarities and differences in stutterers' and nonstutterers' ratings of specific speaking situations were identified.     

Acoustic measures of stutterers' and nonstutterers' fluency in two speech contexts

The purpose of this study was to compare stutterers' and nonstutterers' fluency during multiple productions of two dissimilar speech contexts. Twenty-two adult stutterers were matched within 1 year of age to 22 nonstutterers. Spectrographic analyses were performed on subjects' five consecutively fluent productions of a simple isolated phrase and a phrase extracted from an oral reading passage. Measures of fluent voice onset time (VOT), and vowel, consonant, and total phrase durations were calculated from the five repetitions of each phrase. From the isolated phrase, there were a total of five fluent durational measures (i.e., one VOT, two vowel, one consonant, & one phrase duration). For the phrase taken from the oral reading passage, six fluent measures were obtained (i.e., one VOT, three vowel, one consonant, & one phrase duration). Results demonstrated that only one of the five measurements taken during the isolated phrase condition was significantly different between the groups. Three of the six measures obtained from the phrase taken from the oral reading condition revealed significant between-group differences. No group differences were associated with the repetitions of either phrase for any of the dependent measures for both groups. These findings suggest that the length and complexity of the speech tasks used to obtain acoustic measures of stutterers' fluency play an important role in the discovery of differences between the fluency of the two groups.     

Effects of gradual increases in sentence length and complexity on children's dysfluency

To systematically evaluate the task demands of changes in utterance length and complexity, 8 normal and 8 stuttering children, ages 3:11-6:4, were administered an elicited imitation task in which the variables of syntactic complexity (as determined by normative age of acquisition) and length were manipulated to appraise their effects upon fluency and accuracy of sentence reproduction. Our findings suggest that fluency breakdown is significantly well correlated with gradual increases in syntactic complexity for both stuttering and normal children, as is sentence replication ability. Length does not appear to be as strong a predictor of fluency characteristics of elicited output. Additionally, we were unable to support a growing clinical impression of subtle language differences between normal and stuttering children; our stuttering subjects did not differ significantly from the normal children in their ability to accurately reproduce a variety of sentence types. The data suggest ways in which task complexity in stuttering therapy for young children might be ordered.     

The effects of word length and visual complexity on verbal reaction times.

Thirty adult subjects learned to associate nonsense names varying in word length with nonsense visual stimuli varying in visual complexity. Simple reaction times (SRTs), visual duration thresholds (VDTs), matching response latencies (MRLs), and naming response latencies (NRLs) were then obtained from these subjects. The data indicate that SRTs, VDTs, and NRLs are significantly related to word length and that VDTs and NRLs are significantly related to visual complexity. There is also a tendency for MRLs to increase with increases in word length, particularly for "no" responses. However, the effects of word length on VDTs, MRLs, and NRLs may be confounded with the number of trials needed to learn the paired associates or with the number of overlearning trials. The data are consistent with an interpretation that motor planning or some form of implicit speech process may be a part of the total time required for the naming response.     

Influences of utterance length and complexity on speech motor performance in children and adults.

The possible influences of utterance length and complexity on speech motor performance were examined by assessing the effects of increased processing demands on articulatory movement stability. Eight 5-year-old children and 8 young adults repeated a 6-syllable phrase in isolation (baseline condition) and embedded in sentences of low and high syntactic complexity. Lower lip movements for the target phrase were analyzed to produce the spatiotemporal index (STI), an index that reflects the stability of lip movement over 10 repetitions of the phrase. It was predicted that movement stability would be lower (reflected by higher values of the STI) for the phrase when it was spoken embedded in complex sentences and that, compared to adults, children's movement output would be more negatively affected by increased processing demands. The STI was significantly increased for the phrase spoken in the complex sentences compared to the baseline condition, and STIs of the children were consistently higher than those of the adults across conditions. These findings provide novel evidence that speech motor planning, execution, or both are affected by processes often considered to be relatively remote from the motor output stage.     

A preliminary comparison of flat affect schizophrenics and brain-damaged patients on measures of affective processing

Flat affect is a major component of schizophrenia and is often also seen in neurological disorders. A preliminary set of comparisons were conducted to delineate neuropsychological mechanisms underlying flat affect in schizophrenia, and new measures are described for the assessment of affective deficits in clinical populations. Subjects were schizophrenic with flat affect (SZs), right brain-damaged (RBD), Parkinson's Disease (PDs), and normal control (NC) right-handed adults. Subjects were administered affective measures of expression and perception in both facial and vocal channels. For both perceptual and expressive tasks the SZs performed significantly less accurately than the NCs and the PDs but did not differ from the RBDs. This was the case for both face and voice. This finding lends support to the speculation that right hemisphere mechanisms, especially cortical ones, may be compromised among schizophrenics with flat affect.     

A comparison of temporal measures of speech using spectrograms and digital oscillograms

To determine whether any systematic differences occur as a result of using spectrograms versus digital oscillograms to make durational measurements, a number of temporal features (e.g., voice onset time, vowel duration, and consonant closure duration) for 3 speakers were independently measured by 2 different investigators. Both experimenters measured the same intervals with conventional spectrograms and with digital oscillograms, separated by at least a 2-week interval. Oscillograms tended to reveal slightly longer vowel durations and more voicing during consonant closure, while spectrograms evidenced slightly longer consonant closure durations. In general, variations between the two types of instrumentation were no more than 8 to 10 ms and are, therefore, of primary consequence only for studies in which quite small temporal differences are critical.     

A comparison of ocular protective measures during carbon dioxide laser laryngoscopy

OBJECTIVE: To determine the efficacy of various eye protection measures during carbon dioxide laser laryngoscopy. DESIGN: A standard medical mannequin was equipped with indicator paper over the eyes and subjected to multiple passes of direct carbon dioxide laser beam contact at 400-mm focal length with powers ranging from 2.5 to 4.0 W during simulated laser microlaryngoscopy. Several different eye protection materials, including silk tape, paper tape, cloth tape, occlusive dressing, and eye pads, were used to cover the eyes and tested for their degree of protection against the laser beam. Thermal injuries were quantified and compared among these protective materials. SETTING: Academic medical center. MAIN OUTCOME MEASURE: Degree of eye protection against the laser beam injury on a scale of 0 to 4. RESULTS: The carbon dioxide laser beam at both 2.5 and 4.0 W produced considerable thermal damage to the indicator paper in the absence of any protective barrier. Among the adhesive protective barriers, moistened cloth tape was the most effective adhesive material against laser beam-induced thermal damage (P<.001). Silk tape and paper tape offered poor protection. Moist eye pads, although not adhesive and therefore unable to maintain eye closure, were very effective barriers against the laser beam. Dry paper tape and dry eye pads were imminently flammable. CONCLUSION: A combination of moistened cloth tape to maintain eye closure coupled with placement of well- moistened cotton-based eye pads over the tape provides excellent eye protection during carbon dioxide laser laryngoscopy.     

A comparison of extratympanic versus transtympanic recordings in electrocochleography.

Detection thresholds, amplitudes and input output curves of cochlear microphonics (CMs), and action potentials (APs) determined by extratympanic electrocochleography (ET ECochG) were compared with those determined by transtympanic (TT) ECochG in the same ears. Two groups were studied: 12 ears in 9 volunteers with normal hearing, and 6 ears in 6 subjects with sensorineural hearing loss. Short tone bursts with frequencies of 0.5, 1, 2 and 4 kHz were used as acoustic stimuli to evoke CMs, and a click was presented to measure the APs. In both groups, although the two approaches produced large differences in amplitudes, nearly identical values were obtained for the CM and AP detection thresholds. The CM and AP input-output curves obtained from mean amplitudes at each intensity in normally-hearing ears had similar slopes with the two approaches. These findings demonstrate the clinical usefulness of ET ECochG.     

A comparison of selected phonatory behaviors of healthy aged and young adults.

Selected phonatory behaviors of healthy aged and young men and women were compared. Inverse-filtered air flow, electroglottograph (EGG), and intraoral air pressure signals were recorded as subjects phonated in each of four conditions: normal, soft, loud, loud/high pitched. Minimum flow offset, flow amplitude, air flow duty cycle, EGG duty cycle, estimated subglottal pressure, and fundamental frequency were derived from the recorded signals and compared among age/gender groups. Males had significantly greater flow amplitude than females regardless of age. Significant Age x Sex interactions were found for fundamental frequency and duty cycle measures. Duty cycles and fundamental frequency increased for males and decreased for females with aging. For the normal phonatory condition, aged men had significantly greater duty cycle measures, flow amplitude, and estimated subglottal pressure than young men. There were significant differences in fundamental frequency and EGG duty cycle between aged and young women during normal phonation. It was concluded that the effects of aging on phonatory behaviors are different in degree and kind for men and women. Fewer significant age-related differences in phonatory measures for women than men were consistent with reports of less age-related laryngeal degeneration in females than males.