Vocal Jitter Research Articles

Facial and Vocal Markers of Schizophrenia Measured Using Remote Smartphone Assessments: Observational Study.

BackgroundMachine learning–based facial and vocal measurements have demonstrated relationships with schizophrenia diagnosis and severity. Demonstrating utility and validity of remote and automated assessments conducted outside of controlled experimental or clinical settings can facilitate scaling such measurement tools to aid in risk assessment and tracking of treatment response in populations that are difficult to engage.ObjectiveThis study aimed to determine the accuracy of machine learning–based facial and vocal measurements acquired through automated assessments conducted remotely through smartphones.MethodsMeasurements of facial and vocal characteristics including facial expressivity, vocal acoustics, and speech prevalence were assessed in 20 patients with schizophrenia over the course of 2 weeks in response to two classes of prompts previously utilized in experimental laboratory assessments: evoked prompts, where subjects are guided to produce specific facial expressions and speech; and spontaneous prompts, where subjects are presented stimuli in the form of emotionally evocative imagery and asked to freely respond. Facial and vocal measurements were assessed in relation to schizophrenia symptom severity using the Positive and Negative Syndrome Scale.ResultsVocal markers including speech prevalence, vocal jitter, fundamental frequency, and vocal intensity demonstrated specificity as markers of negative symptom severity, while measurement of facial expressivity demonstrated itself as a robust marker of overall schizophrenia symptom severity.ConclusionsEstablished facial and vocal measurements, collected remotely in schizophrenia patients via smartphones in response to automated task prompts, demonstrated accuracy as markers of schizophrenia symptom severity. Clinical implications are discussed.

Effect of the vocal tract filtering on the measurement of vocal cycle perturbations

Jitter and shimmer appear as symptoms of disordered voices and they are defined as the cycle-to-cycle variation of the cycle length and cycle amplitude, respectively. The frequency modulation of the phonatory excitation, i.e. vocal jitter, causes amplitude modulation (shimmer) of the speech signal due to the action of the vocal tract transfer function. In this Letter, the authors investigate the extent to which the vocal tract filtering affects the accuracy of measurement of vocal cycle perturbations of the phonatory excitation. To achieve this goal, the direct digital synthesiser is used to generate a series of glottal excitation cycles with the desired amount of vocal perturbations that crosses the vocal tract model to produce a set of 231 stimuli of sustained vowels [a]. Praat is used to measure the amount of perturbations. Results show that the values of the input shimmer inserted in the glottal excitation are smaller than the values measured by Praat. An undesired amount of shimmer is generated in the speech signal when the glottal excitation signal perturbed with jitter crosses through the vocal tract.

Analysis of Fundamental Frequency, Jitter and Shimmer in Stuttered and Non-Stuttered Speech of Marathi Language

Stuttering is one of the complex speech disorder which lead speech unintelligible to other and ASR system. In this paper Fundamental frequency (f0), vocal jitter and shimmer were measures the numerical words of 17 Stuttering (PWS) (i.e. 13 Male and 4 female) and 25 Non-Stutterers (NS) (i.e. 15 male 10 female) belongs to the Marathi Language. Jitter and shimmer are measurements of the cycle - to - cycle variations of F0 frequency and amplitude, respectively, which were largely used to describe pathological voice quality. The experiment performed with Pasrelmouth Praat Scripts in Python. This is the first attempt for the Marathi Language. Shimmer were shows the negligible difference between PWS and NS speech samples.

Singing voice: acoustic parameters after vocal warm-up and cool-down

Purpose: The aim of this study was to evaluate the effect of the vocal warm-up and cool-down on the singing voice through Fundamental Frequency (F0), Jitter, Shimmer and harmonics-to-noise ratio (HNR).Methods: Thirty-two female singing students were recorded four times while uttering the vowel [a] for at least 5''. The first two recordings were collected before and after a vocal warm-up session and the last two before and after a vocal cool-down session. Between those sessions the participants underwent an intense vocal activity.Results: Results showed significant variations in the average values of the parameters measured. The mean value of the F0 after intense vocal activity turned to be higher than the one measured before the warm-up session, as well as the mean F0 measured after singing compared to the one measured after the vocal warm-up. On the other end, the mean F0 after the vocal cool-down resulted to be lower than that measured before. After the vocal warm-up session Jitter and Shimmer decreased while HNR increased. In addition, a decrease was detected in comparison with the average value of Jitter and Shimmer before vocal warm-up and after vocal cool-down, whereas HNR increased. There was also a decrease between the Shimmer before the vocal warm-up and after an intense phonatory activity while HNR increased.Conclusions: Our study highlights the effect of the vocal warm-up on acoustic parameters. The reduction in F0 observed after the cool-down session confirms its positive effect in helping professional vocal recovery and reducing vocal fold tension.

Effects of a Voice Therapy Program for Patients with Muscle Tension Dysphonia

Objective: This study aimed to verify the effects of a voice therapy program focusing on patients with muscle tension dysphonia (MTD). Patients and Methods: The sample comprised 30 participants diagnosed with MTD, 8 men and 22 women, none of whom was a voice professional. The assessments and reassessments employed the perceptual-auditory protocol GRBASI, measures of maximum phonation times, s/z ratio, and acoustic voice analysis. The voice therapy program included indirect and direct therapy approaches. Results: All parameters assessed using the GRBASI protocol improved following treatment, particularly in regard to lowering voice strain, which is important when treating MTD. The average overall maximum phonation times increased from 8.15 to 10.8 s, while the average s/z ratio did not significantly change. Among the various acoustic parameters, a positive difference was observed for vocal jitter and shimmer. Conclusions: The therapeutic approach adopted in this study proved effective in the treatment of primary and secondary MTD. Speech therapy favored lower phonation effort, lowered vocal strain, and adequacy of adjustment of laryngeal muscles.

Testing the reliability of Grade, Roughness and Breathiness scores by means of synthetic speech stimuli

This article describes a synthesizer of disordered voices and reports a test of the reliability of Grade, Roughness, and Breathiness scores assigned to synthetic stimuli by eight expert listeners in two sessions. Speech stimuli [a], [i], [u], [ai], and [ia] were synthesized with three values of vocal frequency and four levels of vocal jitter and pulsatile additive noise each. The agreement and correlation of scores assigned by the same rater in different sessions, or by different raters in the same session, accord with published data. Only a small part of the variance of the arithmetic differences between the scores that are assigned to the same stimulus is explained by the stimuli properties. The conclusion is that differences between scores that are assigned to the same stimulus are not attributable to biases of individual raters; such biases would shift all the scores assigned on a scale, and the shift would be interpretable in terms of the properties of the stimuli.

Joint Source-Filter Optimization for Accurate Vocal Tract Estimation Using Differential Evolution

In this work, we present a joint source-filter optimization approach for separating voiced speech into vocal tract (VT) and voice source components. The presented method is pitch-synchronous and thereby exhibits a high robustness against vocal jitter, shimmer and other glottal variations while covering various voice qualities. The voice source is modeled using the Liljencrants-Fant (LF) model, which is integrated into a time-varying auto-regressive speech production model with exogenous input (ARX). The non-convex optimization problem of finding the optimal model parameters is addressed by a heuristic, evolutionary optimization method called differential evolution. The optimization method is first validated in a series of experiments with synthetic speech. Estimated glottal source and VT parameters are the criteria used for comparison with the iterative adaptive inverse filter (IAIF) method and the linear prediction (LP) method under varying conditions such as jitter, fundamental frequency (f0) as well as environmental and glottal noise. The results show that the proposed method largely reduces the bias and standard deviation of estimated VT coefficients and glottal source parameters. Furthermore, the performance of the source-filter separation is evaluated in experiments using speech generated with a physical model of speech production. The proposed method reliably estimates glottal flow waveforms and lower formant frequencies. Results obtained for higher formant frequencies indicate that research on more accurate voice source models and their interaction with the VT is necessary to improve the source-filter separation. The proposed optimization approach promises to be a useful tool for future research addressing this topic.

Vocal Indices of Stress: A Review

Identification of stress patterns in the voice has multiple potential applications. The objective was to review literature pertaining to the effects of various forms of stress upon the healthy voice. Literature review, discussion of results, and direction for further study. This review article offers a model of stress and a review of the historical and recent research into the effects of stress on the voice. Electronic databases were searched using the key words. No studies were excluded on the basis of design; however, an attempt was made to include in the discussion studies which primarily address physiological and acoustic vocal parameters. The results of greater than 50 studies examining the effect of stressors ranging from lie and guilt to high altitude and space flight upon the voice were included in the review. Increase in fundamental frequency is the most commonly reported effect of stress in well-controlled trials. The trend, however, is not universal. A reduction in noise as reflected by the diminished vocal jitter is reported, but less frequently. Stress types, gender, and individual differences in baseline autonomic tone may explain the primarily equivocal findings of effects of stressor exposure or perceived stress on voice; and as such, the article concludes with a discussion of directions for future study.

The existence of phonatory instability in multiple sclerosis: an acoustic and electroglottographic study

Dysarthria and phonatory symptomatology are often reported by patients suffering from multiple sclerosis (MS), but have been poorly investigated, although related to life quality. The objective of the study was to investigate the phonatory function in MS patients using objective measures. The speech of 64 MS patients and 64 pair-matched controls was recorded and analyzed using electroglottography, a physiological method that measures the electrical conductance during the opening and closing phases of the vibrating vocal folds. Electroglottographic parameters were correlated with clinical and MRI features. Most of the variables that have been used for the analysis of voice (vocal jitter P = 0.041, standard deviation of the average fundamental frequency P = 0.018, and the mean fundamental frequency of the vibrating vocal folds P = 0.025) differentiated the MS group from the control group. Phonatory function is impaired in MS patients, and physiological methods, such as electroglottography, are useful tools to assess it.

Representation of the vocal roughness of aperiodic speech sounds in the auditory cortex

Aperiodicity of speech alters voice quality. The current study investigated the relationship between vowel aperiodicity and human auditory cortical N1m and sustained field (SF) responses with magnetoencephalography. Behavioral estimates of vocal roughness perception were also collected. Stimulus aperiodicity was experimentally varied by increasing vocal jitter with techniques that model the mechanisms of natural speech production. N1m and SF responses for vowels with high vocal jitter were reduced in amplitude as compared to those elicited by vowels of normal vocal periodicity. Behavioral results indicated that the ratings of vocal roughness increased up to the highest jitter values. Based on these findings, the representation of vocal jitter in the auditory cortex is suggested to be formed on the basis of reduced activity in periodicity-sensitive neural populations.

The evaluation of the causes of subjective voice disturbances after thyroid surgery

Background Voice changes following thyroidectomy is a rare form of morbidity not infrequently encountered. Injury to the recurrent laryngeal nerve or external branch of the superior laryngeal nerve is the most well-known cause of post-thyroidectomy voice disturbances. However, voice dysfunction is a more complex entity. The aim of the current study was to assess the possible factors that influence voice changes after thyroidectomy. Methods Forty-eight consecutive patients who had undergone thyroidectomy were studied. The acoustic voice analysis (mean vocal fundamental frequency [Fo], mean percentage vocal jitter and shimmer, and noise-to-harmonic ratio) and videolaryngostroboscopic examination of these patients were performed preoperatively, on the second postoperative day, and 3 months after the operation. The presence of subjective voice changes was recorded prospectively based on a symptom scale. Results No major complications occurred perioperatively or in the postoperative period. Videolaryngostroboscopic examinations were normal in all patients before and after thyroidectomy. Eighteen (37.5%) patients complained of subjective voice changes in the early postoperative period and 7 (14.6%) of these were still uncomfortable after 3 months. Although the difference was significant by means of all acoustic voice parameters measured in the early postoperative period, Fo is the only parameter that continues to be significant after 3 months. Conclusions Irrespective from recurrent laryngeal nerve and/or injuries to the external branch of the superior laryngeal nerve, voice may temporarily be affected by thyroidectomy. Most of the subjective complaints and acoustic voice parameters return to normal in a few months after surgery.

Decomposition of Vocal Cycle Length Perturbations into Vocal Jitter and Vocal Microtremor, and Comparison of Their Size in Normophonic Speakers

Summary: A statistical method that enables raw vocal cycle length perturbations to be decomposed into perturbations ascribed to vocal jitter and vocal tremor is presented, together with a comparison of the size of jitter and tremor. The method is based on a time series model that splits the vocal cycle length perturbations into uncorrelated cycle-to-cycle perturbations ascribed to vocal jitter and supra-cycle perturbations ascribed to vocal tremor. The corpus was composed of 114 vocal cycle length time series for sustained vowels [a], [i], and [u] produced by 22 male and 16 female normophonic speakers. The results were the following. First, 100 out of 114 time series were decomposed successfully by means of the time series model. Second, vocal perturbations ascribed to tremor were significantly larger than perturbations ascribed to jitter. Third, the correlation between vocal jitter and vocal tremor was moderate, but statistically significant. Fourth, small but statistically significant differences were observed among the three vowel timbres in the relative jitter and the arithmetic difference of jitter and tremor. Fifth, the differences between male and female speakers were not statistically significant in the relative raw perturbations, the relative jitter, or the modulation level owing to tremor.

Stochastic models of jitter.

This study presents stochastic models of jitter. Jitter designates small, random, involuntary perturbations of the glottal cycle lengths. Jitter is a base-line phenomenon that may be observed in all voiced speech sounds. Knowledge of its properties is therefore relevant to the acoustic modeling, analysis, and synthesis of voice quality. Also, models of jitter are conceptual frameworks that enable experimenters and clinicians to distinguish jitter in particular from aperiodic cycle length patterns in general. Vocal jitter is modeled by means of the ribbon model of the glottal vibration combined with stochastic models of the disturbances of the instantaneous frequency. The disturbance model comprises correlation-free noise and vocal microtremor. Properties of jitter that are simulated are the stochasticity, stationarity, and normality of the decorrelated cycle length perturbations, the size of decorrelated jitter, the correlation between the perturbations of neighboring glottal cycles, the modulation level and modulation frequency owing to microtremor, the asynchrony between external disturbances and glottal cycles, the dependence of the size of jitter on the average glottal cycle length, and the relation between jitter and laryngeal pathologies. Modeled jitter is discussed in the light of measured jitter, as well as the physiological and statistical plausibility of the model parameters.

Vocal Characteristics of Older Adults and Stereotyping

Two studies extended the study of the nonverbal correlates of age stereotypes. In Study 1, 40 young listeners assessed the age of 30 elderly speakers from three age groups: 60–69, 70–79, 80 and over. As expected, perceived age increased linearly with age group, although greater variability was found in judgments of male than of female speakers. For male speakers, mean vocal volume (intensity) and standard deviations in vocal volume were positively correlated with chronological and perceived age. For female speakers, mean pitch, standard deviations in pitch, and vocal jitter were positively correlated with chronological and perceived age. In Study 2, 40 young listeners selected trait sets corresponding to 3 positive and 3 negative elderly stereotypes to describe 6 young-old and 6 old-old speakers. As predicted, listeners associated the old-old voices of females (but not males) with fewer positive stereotypes than the young-old female voices. In addition, young-old male voices were associated with significantly fewer positive stereotypes than young-old female voices. Finally, male participants chose fewer positive stereotypes for young-old male voices than did female participants. These results provide information on the ways in which vocal characteristics may serve to activate stereotypes in interaction.

Acoustic analysis of the speaking voice after thyroidectomy

Voices of 47 female patients were analyzed before and after thyroidectomy, with preservation of the recurrent and superior laryngeal nerves and normal vocal fold motility during the observation period. A mean decrease of the speaking fundamental frequency (SFF) of 12 Hz was found on day 4; in 8 patients the postoperative vocal pitch was more than 2 semitones lower. The distance between the highest and lowest F0 during speaking was diminished (speech was more monotone) and the vocal jitter was elevated. In the frequency spectrum, there was a diminished prominence of the harmonics. The other spectral parameters (as the slope of the spectrum and the H1/H2 ratio) were unchanged. All changes had disappeared the fifteenth day, except for a lower SFF (> 2 semitones) in 2 cases. It is concluded that after normal dissection of the laryngeal nerves, and in the absence of vocal fold paresis, other reasons for voice changes immediately after thyroidectomy remain: alterations in the neck muscles, in the laryngeal mucosa, and in the patient's general condition. Although the effects seem limited and of short duration, knowledge of them is helpful when informing the patient before thyroid surgery.

A new jitter-algorithm to quantify hoarseness: an exploratory study

This paper presents an empirical study of the validity and reliability of a new method to quantify hoarseness or roughness of the voice by measuring vocal jitter which refers to the temporal irregularities of the vibration process of the vocal folds. Whereas it is quite possible to measure jitter in recordings of sustained vowels elicited in laboratory conditions, there seems to be no reliable method of measuring it in connected speech. This problem arises in forensic speaker identification (S I), where speech samples from non-cooperative speakers have to be analysed . Therefore a new jitter-algorithm which was specifically developed for application in forensic SI is rested. Seven male German speakers with different kinds of pathological hoarseness and seven speakers with normal voices served as subjects. The results show that the algorithm reliably measures jitter not only based on isolated vowels bur also based on vowels in connected speech, thus allowing for quantification of an additional parameter in forensic SI.

Effect of Microphone Type and Placement on Voice Perturbation Measurements

This study was conducted to explore the effects of microphone type (dynamic vs. condenser) and pattern (omnidirectional vs. cardioid) on the extraction of voice perturbation measures for sustained phonation. Also of interest were the effects of distance and angle between the source and the microphone. Four professional-grade and two consumer-grade microphones were selected for analysis. Synthesized phonation with different amplitude and frequency modulations at fundamental frequencies of 100 Hz and 300 Hz were presented over a loudspeaker. Human phonation was also included to test the validity of loudspeaker presentations. Three microphone distances (4 cm, 30 cm, 1 m) and three angles (0 degree, 45 degrees, 90 degrees) were used for microphone placement. Among the professional grade microphones, the cardioid condenser type had the smallest effect on perturbation measures. In general, condenser types gave better results than dynamic types. Microphones with an unbalanced output did not perform as well as those with balanced outputs. Microphone sensitivity and distance had the largest effect on perturbation measures, making it difficult to resolve normal vocal jitter at anything but a few centimeters from the mouth. Angle had little effect for short distances, but a greater effect for longer distances. These conclusions are preliminary because the sampling of microphones, distances, and signal types was very coarse. The study serves only to chart the course for future work.

The Effect of Sustained Phonation at High and Low Pitch on Vocal Jitter and Shimmer

Looking for possible signs of vocal fatigue, acoustic waveform perturbation was measured in normal female subjects during sustained phonation at various fundamental frequencies (Fo). At none of the pitch levels a rise of the jitter or the shimmer was found after 25 min of vocalization. On the other hand, an effect of Fo was seen from the start: above the habitual speaking Fo of our subjects' voices there was a tendency for the jitter to be higher and for the shimmer to be lower.

Acoustic characteristics of post-thyroplasty patients.

This study investigated changes in voice quality after thyroplasty type I in eight adults with unilateral vocal fold paralysis. A silicone rubber implant was inserted through a window in the thyroid ala and placed between the inner and outer perichondrium to externally medialize the abducted vocal fold. Measures of fundamental frequency (vocal pitch), pitch range, maximum phonation time, s/z ratio, pitch perturbation (vocal jitter), and amplitude perturbation (vocal shimmer) were made 1 to 2 weeks preoperatively and 1 month postoperatively. Postoperative voice quality was characterized by an improved pitch range, phonation time, s/z ratio, and pitch and amplitude perturbation. No change was noted in fundamental frequency. Changes in postoperative voice quality were unrelated to the subjects' preoperative age, sex, etiology, and duration of the paralysis.

Validity and reliability of nonverbal voice measures as indicators of stressor‐provoked anxiety

To determine the validity and reliability of vocal jitter, tenseness, and pitch as measures of stressor-provoked anxiety, 88 women representing three coping styles (Highly Anxious, Truly Low Anxious, and Repressor) phonated vowels, reported anxiety, and provided measures of muscle tension, heart rate, and sweating 2 weeks before, the day before, and 1 week after stressful exams. Greater self-reported anxiety, sweating, and heart rate on the day before versus the other occasions confirmed the day before was the most stressful occasion. Results suggest excellent validity and reliability for Jitter as an indicator of stressor-provoked anxiety.