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Biomedical subjects

T Shipp

Publications and source records attributed to T Shipp.

At least 19 recordsLinked to original sources
PubMed1999

Genetic sonogram scoring index: accuracy and clinical utility.

We sought to evaluate the accuracy of the genetic sonogram scoring index in detecting Down syndrome fetuses in a high-risk population. Women referred for genetic sonogram scoring index based on increased risk for aneuploidy were prospectively evaluated. Each fetus was assigned a score based on our previously published genetic sonogram scoring index. A score of 1 or greater was an indication for karyotype determination. Of 1076 patients (1118 fetuses) in the study group, follow-up data were available for 1030 (92%), eight of whom had Down syndrome (prevalence 0.8%). Three fetuses with Down syndrome had a genetic sonogram scoring index of 0, and for one of these the mother was 42 years old. One affected fetus had a score of 1 and the other four had scores of 2 or greater. Using a genetic sonogram scoring index of 1 or greater (age not considered), five of eight fetuses with Down syndrome (62.5%) were identified, as well as 150 of 1030 (14.6%) of normals. Down syndrome was undetected in three fetuses of 1030 (1 in 343) or 0.29%. In addition, when all women 40 years old or older underwent karyotype testing regardless of their sonographic findings, six of eight Down syndrome fetuses were identified (75%), as well as 271 of 1030 (26.3%) of normals. The number of cases of Down syndrome not detected was two in 1030 (1 in 515) or 0.19%. In conclusion, the genetic sonogram scoring index was used to identify approximately 75% of fetuses with Down syndrome, with amniocentesis being recommended in 26.7% of a high-risk population.

Adult↗
PubMed1994

Speech measures indicating workload demand.

Heart rate and six speech measures were evaluated using a manual tracking task under different workload demands. Following training, 17 male subjects performed three task trials: a difficult trial, with a $50 incentive for successful performance at a very demanding level; an easy trial, with a $2 incentive for successful performance at a simple level; and a baseline trial, in which there was physiological monitoring but no tracking performance. Subjects counted aloud during the trials. It was found that heart rate, speaking fundamental frequency (pitch), and vocal intensity (loudness) increased significantly with workload demands. Speaking rate showed a marginal increase, while vocal jitter and vocal shimmer did not show reliable changes. A derived speech measure, which statistically combined information from all other speech measures except shimmer, was also evaluated. It increased significantly with workload demands and was surprisingly robust in showing differences for individual subjects. It appears that speech analysis can provide practical workload information.

Adult↗
PubMed1992

An adaptive method for tracking voicing irregularities.

A method has been developed for tracking irregularities in the acoustic waveform of a sustained phonation using the adaptive Wiener filter. Irregularities are determined by the technique of correlation cancellation. The algorithm is evaluated using sustained vowels produced by a formant synthesizer and by subjects with and without phonatary disorders. Results indicate that the method is capable of differentiating between normal and abnormal voices. Most significantly, however, it can also track sporadic or nonstationary irregularities in the shape of an individual acoustic wavelet. This method is expected to be a useful tool for the acoustics analysis of voice production.

Adult↗
PubMed1988

Tape recorder effects on jitter and shimmer extraction.

To test for possible contamination of acoustic analyses by record/reproduce systems, five sine waves of fixed frequency and amplitude were sampled directly by a computer and recorded simultaneously on four different tape formats (audio and FM reel-to-reel, audio cassette, and video cassette using pulse code modulation). Recordings were digitized on playback and with the direct samples analyzed for fundamental frequency, amplitude, jitter, and shimmer using a zero crossing interpolation scheme. Distortion introduced by any of the data acquisition systems is negligible when extracting average fundamental frequency or average amplitude. For jitter and shimmer estimation, direct sampling or the use of a video cassette recorder with pulse code modulation are clearly superior. FM recorders, although not quite as accurate, provide a satisfactory alternative to those methods. Audio reel-to-reel recordings are marginally adequate for jitter analysis whereas audio cassette recorders can introduce jitter and shimmer values that are greater than some reported values for normal talkers.

Acoustic Stimulation↗
PubMed1985

Intrinsic laryngeal muscle activity in a spastic dysphonia patient.

EMG activity from four intrinsic laryngeal muscles (thyroarytenoid, posterior cricoarytenoid, interarytenoid, and cricothyroid) was obtained from one female spastic dysphonia patient while she performed a variety of speech and nonspeech tasks. These tasks were performed before and during a period of temporary unilateral laryngeal muscle paralysis. In the nonparalyzed condition, adductory muscle activity showed intermittent sudden increases that coincided with momentary voice arrests. These muscle patterns and accompanying voice interruptions were not present either when speech was produced in falsetto register or at anytime during the paralysis condition. The data suggest that individuals with this type of spastic dysphonia have normal morphology of recurrent laryngeal nerves and intrinsic laryngeal muscles, which means that the triggering mechanism(s) for spastic dysphonia symptoms must be located at some point neurologically upstream from the larynx.

Combined Modality Therapy↗
PubMed1985

Study of subglottal air pressure during Hindi stop consonants.

This study examines subglottal air pressure (Ps) variations in Hindi stop consonants. The stops were produced in initial, medial and final positions and under different stress conditions in nonsense utterances of the type CV, VCV and VC which were embedded in a frame sentence. The results show no systematic correlation between Ps variations during the oral closure of the stops and the voicing and/or aspiration contrasts associated with them. However, aspiration and a momentary drop in Ps immediately after the release of aspirated stops seem to be systematically related. A systematic relationship between a momentary increase in Ps and production of stress is also observed. The variations in Ps associated with the production of stop consonants appear to be reflections of the changes in the glottal and supraglottal impedances. Ps variations related to normal stress appear to be controlled by the phonatory system rather than the respiratory system. On the other hand, for the implementation of heavy or emphatic stress, the phonatory and the respiratory systems appear to function synergistically.

Adult↗
PubMed1984

Physiologic stages of vocal reaction time.

A simple vocal reaction time (RT) task was performed by 10 male subjects while measures from intrinsic laryngeal muscles and subglottal air pressure were obtained simultaneously. Based only on each subject's fastest time among 15 trials, RT values were similar to the latencies previously observed in normal subjects. The mean of the subjects' fastest trials was 185 ms (range: 160-250 ms). Shortest latency values obtained for each measure were interarytenoid muscle, 50 ms; thyroarytenoid muscle, 60 ms; posterior cricoarytenoid muscle, 80 ms; subglottal air pressure rise, 125 ms. From these data estimates were made of 115 ms for the shortest respiratory system latency and 25 ms for the minimal central processing time. These data suggest that fastest vocal RTs are determined principally by the temporal constraints involved in activating pulmonary rather than laryngeal structures.

Adult↗
PubMed1981

Current evidence for the existence of laryngeal macrotremor and microtremor.

To test for the existence of laryngeal "microtremors" two experiments were conducted on humans. The first analyzed the acoustic characteristics of observable tremors (macrotremors) in the voice of singers using vocal vibrato and in pathologic subjects producing vocal tremor. In both of these groups acoustic oscillations between 4 and 8 Hz were found. The second study, using a normal subject, sampled electromyographic (EMG) activity from laryngeal and arm muscles during isometric contraction to determine if a periodic component (microtremor) was present in either muscle's contraction pattern. A 9-Hz signal was detected in limb muscle contraction, whereas no periodicity was found in signals from laryngeal muscles. The application of these findings to the theory behind voice "stress" analyzers is discussed

Female↗
PubMed1979

Predicting vocal frequency from selected physiologic measures.

Simultaneous physiologic measures were obtained on four young adult male subjects as they sustained phonation at seven frequencies within their modal-to-falsetto voice range. Data were analyzed using a multiple regression program to determine the contribution of each measure singly and in combination with other measures to the prediction of the resultant voice frequency. Results showed that by far the best predictor was cricothyroid muscle activity for both the pooled data model, and for each individual subject. The contribution of subglottal air pressure and thyroarytenoid muscle activity increased the variance explained by only 4% while the measure of vertical laryngeal position was a significant factor in only one subject's predictive model. Partial models from the pooled data explained from 67% to 73% of the variance; whereas the obtained measures for individual subjects explained from 90% to 94% of the variance.

Adult↗
PubMed1978

Minimal reaction times for phonatory initiation.

The maximum speed at which voluntary vocal and digital responses can be initiated was investigated in 15 male and 15 female neurologically normal adults using simple reaction time (RT) methodology. All subjects were pretrained to respond as quickly as possible to stimulus onset following a computer-controlled preparatory interval. Voluntary minimal RTs for phonation initiation were studied as a function of (1) stimulus type (auditory and somesthetic), (2) prephonatory vocal-fold position (abducted and adducted), and (3) subject's lung volume (75%, 50%, and 25% VC). The average minimal vocal RT across subjects was 195 msec, and the fastest recorded vocal RT was 120 msec. Although vocal responses to an auditory stimulus were somewhat shorter than to a somesthetic stimulus, neither these differences nor the RTs between sexes were statistically significant except that females had shorter vocal RTs from an abducted prephonatory vocal-fold position. Shorter vocal RTs were obtained when phonation was initiated at midlung volume than at the lung volume extremes, and for both sexes the average digital RTs were significantly shorter than vocal RTs.

Acoustic Stimulation↗
PubMed1975

Vertical laryngeal position during continuous and discrete vocal frequency change.

Six young adult male subjects produced sustained phonation throughout their vocal frequency ranges: first, in a glissando or continuous frequency change maneuver, and second, in discrete intervals at separate trials. Measures of intrinsic and extrinsic laryngeal muscle activity and vertical laryngeal position were related to voice fundamental frequency in the two conditions. Each subject consistently positioned his larynx at a resting level when he was instructed to relax or when he was not performing experimental tasks. All larynx positions during experimental tasks were measured as deviations from this resting level. Subjects showed a close correspondence between their vertical laryngeal positions and voice frequencies--more so for the glissando maneuver than for changes in discrete frequency tasks. In general, subjects lowered their larynges from the resting position for low-frequency phonation and raised their larynges for higher fundamental frequencies. Absolute larynx position for the same frequency was quite varied both within and between subjects. Vertical laryngeal position during phonation most often was directly related to the activity of the thyrohyoid and sternothyroid muscles. Neither vertical laryngeal movement nor intrinsic laryngeal activity showed any pattern of relationship to changes between modal and falsetto voice registers.

Action Potentials↗