Beta-adrenergic blockade and voice: a double-blind, placebo-controlled trial

Ecologically valid speech collection in behavioral research: The Ghent Semi-spontaneous Speech Paradigm (GSSP)

This paper introduces the Ghent Semi-spontaneous Speech Paradigm (GSSP), a new method for collecting unscripted speech data for affective-behavioral research in both experimental and real-world settings through the description of peer-rated pictures with a consistent affective load. The GSSP was designed to meet five criteria: (1) allow flexible speech recording durations, (2) provide a straightforward and non-interfering task, (3) allow for experimental control, (4) favor spontaneous speech for its prosodic richness, and (5) require minimal human interference to enable scalability. The validity of the GSSP was evaluated through an online task, in which this paradigm was implemented alongside a fixed-text read-aloud task. The results indicate that participants were able to describe images with an adequate duration, and acoustic analysis demonstrated a trend for most features in line with the targeted speech styles (i.e., unscripted spontaneous speech versus scripted read-aloud speech). A speech style classification model using acoustic features achieved a balanced accuracy of 83% on within-dataset validation, indicating separability between the GSSP and read-aloud speech task. Furthermore, when validating this model on an external dataset that contains interview and read-aloud speech, a balanced accuracy score of 70% is obtained, indicating an acoustic correspondence between the GSSP speech and spontaneous interviewee speech. The GSSP is of special interest for behavioral and speech researchers looking to capture spontaneous speech, both in longitudinal ambulatory behavioral studies and laboratory studies. To facilitate future research on speech styles, acoustics, and affective states, the task implementation code, the collected dataset, and analysis notebooks are available.

Effects of trace element dietary supplements on voice parameters and some physiological and psychological parameters related to stress

Trace elements, often used as dietary supplements, are widely accessible without prescription at pharmacies. Pronutri has pioneered Nutripuncture®, a methodology that utilizes orally consumed trace elements to elicit a physiological response akin to that of acupuncture. Pronutri has empirically observed that the user's voice becomes deeper following an exclusive ingestion procedure. Given that alterations in vocal characteristics are often linked to stress, the Pronutri researchers postulated that the pills have the capacity to promptly alleviate stress upon ingestion. Nevertheless, there is a lack of scientific substantiation about the impact of these supplements on voice (or stress) indicators. The aim of this research was to determine whether there is a consistent impact of trace element ingestion on vocal characteristics, namely the fundamental frequency of the voice, as well as other physiological and psychological stress measurements. In order to achieve this objective, we have devised a unique methodology to examine this hypothesis. This involves conducting a monocentric crossover, randomized, triple-blind, placebo-controlled trial with a sample size of 43 healthy individuals. This study demonstrates that compared to placebo tablets, consuming 10 metal traces containing tablets at once is enough to cause noticeable changes in the vocal spectrum in the direction of an improvement of the voice timbre "richness", and a decrease in the occurrence of spontaneous electrodermal activity, suggesting a stress reduction. However, there were no significant changes observed in the other parameters that were tested. These parameters include vocal measures such as voice frequency F0, standard deviation from this frequency, jitter, and shimmer. Additionally, physiological measures such as respiratory rate, oxygenation and heart rate variability parameters, as well as psychological measures such as self-assessment analogic scales of anxiety, stress, muscle tension, and nervous tension, did not show any significant changes. Ultimately, our research revealed that the ingestion of 10 trace elements pills may promptly elicit a targeted impact on both vocal spectrum and electrodermal activity. Despite the limited impact, these findings warrant more research to explore the long-term effects of trace elements on voice and stress reduction.

Acoustic and prosodic speech features reflect physiological stress but not isolated negative affect: a multi-paradigm study on psychosocial stressors

Heterogeneity in speech under stress has been a recurring issue in stress research, potentially due to varied stress induction paradigms. This study investigated speech features in semi-guided speech following two distinct psychosocial stress paradigms (Cyberball and MIST) and their respective control conditions. Only negative affect increased during Cyberball, while self-reported stress, skin conductance response rate, and negative affect increased during MIST. Fundamental frequency (F0), speech rate, and jitter significantly changed during MIST, but not Cyberball; HNR and shimmer showed no expected changes. The results indicate that observed speech features are robust in semi-guided speech and sensitive to stressors eliciting additional physiological stress responses, not solely decreases in negative affect. These differences between stressors may explain literature heterogeneity. Our findings support the potential of speech as a stress level biomarker, especially when stress elicits physiological reactions, similar to other biomarkers. This highlights its promise as a tool for measuring stress in everyday settings, considering its affordability, non-intrusiveness, and ease of collection. Future research should test these results' robustness and specificity in naturalistic settings, such as freely spoken speech and noisy environments while exploring and validating a broader range of informative speech features in the context of stress.

Acoustic speech features in social comparison: how stress impacts the way you sound

The use of speech as a digital biomarker to detect stress levels is increasingly gaining attention. Yet, heterogeneous effects of stress on specific acoustic speech features have been observed, possibly due to previous studies' use of different stress labels/categories and the lack of solid stress induction paradigms or validation of experienced stress. Here, we deployed a controlled, within-subject psychosocial stress induction experiment in which participants received both neutral (control condition) and negative (negative condition) comparative feedback after solving a challenging cognitive task. This study is the first to use a (non-actor) within-participant design that verifies a successful stress induction using both self-report (i.e., decreased reported valence) and physiological measures (i.e., increased heart rate acceleration using event-related cardiac responses during feedback exposure). Analyses of acoustic speech features showed a significant increase in Fundamental Frequency (F0) and Harmonics-to-Noise Ratio (HNR), and a significant decrease in shimmer during the negative feedback condition. Our results using read-out-loud speech comply with earlier research, yet we are the first to validate these results in a well-controlled but ecologically-valid setting to guarantee the generalization of our findings to real-life settings. Further research should aim to replicate these results in a free speech setting to test the robustness of our findings for real-world settings and should include semantics to also take into account what you say and not only how you say it.

Propranolol versus Other Selected Drugs in the Treatment of Various Types of Anxiety or Stress, with Particular Reference to Stage Fright and Post-Traumatic Stress Disorder

Propranolol, a non-cardioselective β1,2 blocker, is most commonly recognised for its application in the therapy of various cardiovascular conditions, such as hypertension, coronary artery disease, and tachyarrhythmias. However, due to its ability to cross the blood-brain barrier and affinity towards multiple macromolecules, not only adrenoreceptors, it has also found application in other fields. For example, it is one of the very few medications successfully applied in the treatment of stage fright. This review focuses on the application of propranolol in the treatment of various types of anxiety and stress, with particular reference to stage fright and post-traumatic stress disorder (PTSD). Both mechanisms of action as well as comparison with other therapies are presented. As those indications for propranolol are, in most countries, considered off-label, this review aims to gather information that can be useful while making a decision about the choice of propranolol as a drug in the treatment of those mental conditions.

Stress Effects on Pharyngeal Air Pressure and Upper Esophageal Sphincter Pressure During Phonation: The Influence of Vocal Tract Semi-Occlusion

OBJECTIVES/HYPOTHESIS

The objective of this study was to determine whether vocal tract semi-occlusion (SOVT) influenced stress effects on pharyngeal air pressure and upper esophageal sphincter (UES) pressure during phonation. Relationships between dysphonia and stress are well recognized but poorly understood. Stress effects act globally on the body, and may be observed beyond intrinsic laryngeal muscles to include pharyngeal muscles and the UES, which contribute to voice modulation. Phonation with SOVT may provide resistance to stress effects on the vocal tract. We hypothesized that stress effects on pharyngeal air pressure and UES pressure would be measurable with a high-resolution, 360° pressure catheter, and that stress effects would be impacted differently by occlusal and non-occlusal phonatory tasks.

METHODS

Ten healthy adults performed sustained vowel tasks (comfortable /a/, and loud /a/), and SOVT tasks (bilabial fricative and straw phonation). Each task was performed during a baseline condition, and during stress induced through a cold pressor task. Pharyngeal air pressure and UES pressure were measured via high-resolution manometry. Changes in pressure between baseline and stress were compared among phonatory tasks.

RESULTS

Stress-induced changes to UES pressure differed by phonatory task (P < 0.01). Stress increased UES pressures during vowels, but had no effect during bilabial fricative, and decreased UES pressures during straw phonation. Change in UES pressure with stress was greater for comfortable /a/ and loud /a/ than straw phonation (P = 0.048 and P = 0.019, respectively), and was not significantly different between comfortable /a/ or loud /a/ and bilabial fricative. Stress-induced changes in pharyngeal air pressure were not significantly different among tasks.

CONCLUSIONS

These findings help identify possible mechanisms underlying the relationship between stress and voice, and point to the utility of SOVT tasks for training vocal tract resistance to stress. This methodology provides a foundation for measuring changes to extra-laryngeal components of the vocal tract during phonation.

Investigating Past Trauma in Laryngoresponders Versus Non-Laryngoresponders: Piloting New Methods in an Exploratory Study

OBJECTIVES/HYPOTHESIS

This exploratory pilot study aimed to probe the relationship between past experiences of trauma in people who self-identify as "laryngoresponders" compared to those who do not. It also explored the communicative context of past traumatic events in laryngoresponders versus non-laryngoresponders.

STUDY DESIGN

Prospective, within-subjects experimental design.

METHODS

29 vocally healthy cisgender women (ages 19 to 56) completed a battery of validated self-report measures relating to their past traumatic experiences. Participants also completed two original self-report measures designed to provide insight about (1) where stress tends to manifest in their body and (2) communicative settings of participants' past trauma.

RESULTS

Six participants (21%) self-identified a predictable laryngeal and/or vocal response to acute stress and thus comprise the laryngoresponders group. Laryngoresponders exhibited worse scores on 75% of all trauma-related variables compared to non-laryngoresponders, and Emotional Neglect was disproportionately represented in laryngoresponders. Participants with a reported history of childhood Emotional Neglect (83% of laryngoresponders, 35% of nonlaryngoresponders) reported quantitatively "less ideal" communication experiences in the context of past traumatic experiences.

CONCLUSIONS

Other investigators identify the larynx as a "vulnerable body pathway" for some women. This pilot study of adult women without voice complaints revealed several commonalities amongst self-reported laryngoresponders, and compels further exploration of the voice-trauma relationship.

Vocal-Stress Diary: A Longitudinal Investigation of the Association of Everyday Work Stressors and Human Voice Features

The human voice conveys plenty of information about the speaker. A prevalent assumption is that stress-related changes in the human body affect speech production, thus affecting voice features. This suggests that voice data may be an easy-to-capture measure of everyday stress levels and can thus serve as a warning signal of stress-related health consequences. However, previous research is limited (i.e., has induced stress only through artificial tasks or has investigated only short-term or extreme stressors), leaving it open whether everyday work stressors are associated with voice features. Thus, our participants (111 adult working individuals) took part in a 1-week diary study (Sunday until Sunday), in which they provided voice messages and self-report data on daily work stressors. Results showed that work stressors were associated with voice features such as increased speech rate and voice intensity. We discuss theoretical, practical, and ethical implications regarding the voice as an indicator of psychological states.

Manipulation of vocal communication and anxiety through pharmacologic modulation of norepinephrine in the Pink1-/- rat model of Parkinson disease

Vocal deficits and anxiety are common, co-occurring, and interacting signs of Parkinson Disease (PD) that have a devastating impact on quality of life. Both manifest early in the disease process. Unlike hallmark motor signs of PD, neither respond adequately to dopamine replacement therapies, suggesting that their disease-specific mechanisms are at least partially extra-dopaminergic. Because noradrenergic dysfunction is also a defining feature of PD, especially early in the disease progression, drug therapies targeting norepinephrine are being trialed for treatment of motor and non-motor impairments in PD. Research assessing the effects of noradrenergic manipulation on anxiety and vocal impairment in PD, however, is sparse. In this pre-clinical study, we quantified the influence of pharmacologic manipulation of norepinephrine on vocal impairment and anxiety in Pink1-/- rats, a translational model of PD that demonstrates both vocal deficits and anxiety. Ultrasonic vocalization acoustics, anxiety behavior, and limb motor activity were tested twice for each rat: after injection of saline and after one of three drugs. We hypothesized that norepinephrine reuptake inhibitors (atomoxetine and reboxetine) and a β receptor antagonist (propranolol) would decrease vocal impairment and anxiety compared to saline, without affecting spontaneous motor activity. Our results demonstrated that atomoxetine and reboxetine decreased anxiety behavior. Atomoxetine also modulated ultrasonic vocalization acoustics, including an increase in vocal intensity, which is almost always reduced in animal models and patients with PD. Propranolol did not affect anxiety or vocalization. Drug condition did not influence spontaneous motor activity. These studies demonstrate relationships among vocal impairment, anxiety, and noradrenergic systems in the Pink1-/- rat model of PD.

Speech as an indicator for psychosocial stress: A network analytic approach

Recently, the possibilities of detecting psychosocial stress from speech have been discussed. Yet, there are mixed effects and a current lack of clarity in relations and directions for parameters derived from stressed speech. The aim of the current study is – in a controlled psychosocial stress induction experiment – to apply network modeling to (1) look into the unique associations between specific speech parameters, comparing speech networks containing fundamental frequency (F0), jitter, mean voiced segment length, and Harmonics-to-Noise Ratio (HNR) pre- and post-stress induction, and (2) examine how changes pre- versus post-stress induction (i.e., change network) in each of the parameters are related to changes in self-reported negative affect. Results show that the network of speech parameters is similar after versus before the stress induction, with a central role of HNR, which shows that the complex interplay and unique associations between each of the used speech parameters is not impacted by psychosocial stress (aim 1). Moreover, we found a change network (consisting of pre-post stress difference values) with changes in jitter being positively related to changes in self-reported negative affect (aim 2). These findings illustrate – for the first time in a well-controlled but ecologically valid setting – the complex relations between different speech parameters in the context of psychosocial stress. Longitudinal and experimental studies are required to further investigate these relationships and to test whether the identified paths in the networks are indicative of causal relationships.

Aerodynamic and Acoustic Voice Measures Before and After an Acute Public Speaking Stressor

Purpose The goal of this study was to determine if differences in stress system activation lead to changes in speaking fundamental frequency, average oral airflow, and estimated subglottal pressure before and after an acute, psychosocial stressor. Method Eighteen vocally healthy adult females experienced the Trier Social Stress Test (TSST) to activate the hypothalamic-pituitary-adrenal axis. The TSST includes public speaking and performing mental arithmetic in front of an audience. At seven time points, three before the stressor and four after the stressor, the participants produced /pa/ repetitions, read the Rainbow Passage, and provided a saliva sample. Measures included (a) salivary cortisol level, (b) oral airflow, (c) estimated subglottal pressure, and (d) speaking fundamental frequency from the second sentence of the Rainbow Passage. Results Ten of the 18 participants experienced a hypothalamic-pituitary-adrenal axis response to stress as indicated by a 2.5-nmol/L increase in salivary cortisol from before the TSST to after the TSST. Those who experienced a response to stress had a significantly higher speaking fundamental frequency before and immediately after the stressor than later after the stressor. No other variable varied significantly due to the stressor. Conclusions This study suggests that the idiosyncratic and inconsistent voice changes reported in the literature may be explained by differences in stress system activation. In addition, laryngeal aerodynamic measures appear resilient to changes due to acute stress. Further work is needed to examine the influence of other stress systems and if these findings hold for dysphonic individuals.

A psychometric investigation of "macroscopic" speech measures for clinical and psychological science

The analysis of vocal expression is a critical endeavor for psychological and clinical sciences and is an increasingly popular application for computer-human interfaces. Despite this, and despite advances in the efficiency, affordability, and sophistication of vocal analytic technologies, there is considerable variability across studies regarding what aspects of vocal expression are studied. Vocal signals can be quantified in a myriad of ways, and their underlying structure, at least with respect to "macroscopic" measures from extended speech, is presently unclear. To address this issue, we evaluated the psychometric properties-notably, the structural and construct validity-of a systematically defined set of global vocal features. Our analytic strategy focused on (a) identifying redundant variables among this set, (b) employing principal components analysis (PCA) to identify nonoverlapping domains of vocal expression, (c) examining the degrees to which the vocal variables are modulated as a function of changes in speech task, and (d) evaluating the relationship between the vocal variables and cognitive (i.e., verbal fluency) and clinical (i.e., depression, anxiety, and hostility) variables. Spontaneous speech samples from 11 independent studies of young adults (>60 s in length), employing one of three different speaking tasks, were examined (N = 1,350). Confounding variables (i.e., sex, ethnicity) were statistically controlled for. The PCA identified six distinct domains of vocal expression. Collectively, vocal expression (defined in terms of these domains) was modulated as a function of speech task and was related to the cognitive and clinical variables. These findings provide empirically grounded implications for the study of vocal expression in psychological and clinical sciences.

Life-cycle exposure of fathead minnows to environmentally relevant concentrations of the β-blocker drug propranolol

Propranolol is a human pharmaceutical β-blocker that has been detected in municipal wastewater effluents at ng/L to low μg/L. To assess the potential of this compound to affect fish, fathead minnow (Pimephales promelas) were exposed for a life cycle in a flow-through system to nominal propranolol concentrations of 0.87 ng/L, 8.7 ng/L, 87 ng/L, 870 ng/L, and 8700 ng/L. Measured propranolol concentrations were below detection for the 2 lowest exposure concentrations, and were 76 ng/L, 580 ng/L, and 7800 ng/L for the 3 highest exposure concentrations. During the 162-d to 165-d exposure, no significant changes in weights or lengths were seen in fathead minnows, although the highest concentration of propranolol did cause a 15% decrease in survival of larval and juvenile stage fish compared with controls. At maturity, there were no significant changes in condition factor, liver-somatic index, or secondary sex characteristics in propranolol-exposed male or female fish. Female gonadosomatic index was significantly decreased in fish exposed to the highest concentrations of propranolol, probably because of increased egg-laying. Fathead minnows from all propranolol exposures produced more eggs than control fish, with fish exposed to 7800 ng/L propranolol producing 70% more eggs per female (p = 0.060), and having significantly increased clutch size (p = 0.008). Egg quality, % fertilization, % hatching, and % deformities in F1 fry were unaffected by propranolol exposure of fish. Propranolol exposure caused no effects in fathead minnows, except at the highest exposure concentration (7800 ng/L), where there were slight decreases in survival of juvenile minnows, and indications of increased reproduction. The present study is important because it is the first to assess the potential for effects in fish exposed to propranolol for a life cycle. Environ Toxicol Chem 2017;36:1644-1651. © 2016 SETAC.

Vocal expression in schizophrenia: Less than meets the ear

Abnormalities in nonverbal communication are a hallmark of schizophrenia. Results from studies using symptom rating scales suggest that these abnormalities are profound (i.e., 3-5 SDs) and occur across virtually every channel of vocal expression. Computerized acoustic analytic technologies, used to overcome practical and psychometric limitations with symptom rating scales, have found much more benign and isolated abnormalities. To better understand vocal deficits in schizophrenia and to advance acoustic analytic technologies for clinical and research applications, we examined archived speech samples from 5 separate studies, each using different speaking tasks (patient N = 309; control N = 117). We sought to: (a) use Principal Component Analysis (PCA) to identify independent vocal expression measures from a large set of variables, (b) quantify how patients with schizophrenia are abnormal with respect to these variables, (c) evaluate the impact of demographic and contextual factors (e.g., study site, speaking task), and (d) examine the relationship between clinically-rated psychiatric symptoms and vocal variables. PCA identified 7 independent markers of vocal expression. Most of these vocal variables varied considerably as a function of context and many were associated with demographic factors. After controlling for context and demographics, there were no meaningful differences in vocal expression between patients and controls. Within patients, vocal variables were associated with a range of psychiatric symptoms-though only pause length was significantly associated with clinically rated negative symptoms. The discussion centers on explaining the apparent discordance between clinical and computerized speech measures.

Factors Associated With Attrition in Randomized Controlled Trials of Vocal Rehabilitation: Systematic Review and Meta-Analysis

OBJECTIVES/HYPOTHESIS

This study aimed to determine the dropout rates and the reasons for dropout in randomized clinical trials of vocal rehabilitation.

STUDY DESIGN

This study used systematic review and meta-analysis (CRD42013003807).

METHODS

We included randomized controlled trials for voice disorders. In June 2015, we searched the following databases: MEDLINE, EMBASE, Cochrane, Clinical Trials, and AJSLP. The titles and abstracts or full texts of articles were independently analyzed by two reviewers. Study quality was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) scale. Our initial research base included more than 8491 articles.

RESULTS

A total of 51 articles were obtained using our eligibility criteria. The low-quality studies evaluated had higher dropout rates (odds ratio: 3.3, 95% confidence interval: 1.04-12.9). Studies with healthy patients (45%) or vocal training versus no training (25%) also had higher dropout rates. Methodological issues seemed to have a greater influence on the dropout rates of the studies included in the co-occurrence matrix.

CONCLUSIONS

Dropout rates of approximately 15% occur in randomized clinical trials of speech therapy when assessed by the Grading of Recommendations Assessment, Development and Evaluation. Studies with lower methodological quality had higher patient loss rates. Methodological and clinical reasons accounted for the highest dropout rates in the studies included in this meta-analysis.

A case study of vocal features associated with galvanic skin response to stressors in a clinical interaction

OBJECTIVE

We investigated vocal characteristics associated with physiologically determined stressful episodes by means of post-hoc acoustic analyses of speech recorded in a clinical setting. Our research addressed the understudied question of which vocal features may serve as cues naturally occurring stress and is the first to explore this issue in a pitch accent language.

METHODS

The vocal profile of a single female patient interacting with a physician was analyzed with standard speech analysis software for acoustic indicators of stress-related arousal determined by galvanic skin response measurements.

RESULTS

Vocal jitter, representing an aspect of voice quality perceived as hoarseness, appeared to increase during and immediately after skin conductance response intervals. Skin conductance levels during the response intervals were negatively correlated with acoustic features used to approximate the perception of voice unsteadiness (slope and standard deviation of fundamental frequency).

CONCLUSION

An acoustic analysis of vocal properties of speech uttered during independently detected skin conductance response intervals revealed individual patterns for some acoustic features linked to stress in earlier studies.

PRACTICE IMPLICATIONS

Non-invasive methods of arousal detection in physician-patient communication based on acoustic analyses of vocal profiles may, in combination with other analyses, help identify stressful events and thus improve the process of medical information gathering and decision-making.

Vocal complaint in physical education teachers and its association with the cardiovascular system

Background

We examined the vocal complaints and evaluated the correlation between the vocal handicap index (VHI) and heart rate variability (HRV) in physical education teachers. We evaluated 46 teachers.

Method

The subjects were investigated regarding voice complaint and the VHI was applied. HRV was recorded at seated rest for ten minutes and it was analyzed in the time, frequency domains, geometric indices and fractal exponents. The three domains of the VHI were correlated with the indices of HRV.

Results

The physical education teachers presented a VHI score much below the standard of the physiological normality. There was correlation of the organic domain of the VHI with the NN50 and pNN50 and correlation of the functional domain and organic domain of the VHI with the HF index of HRV.

Conclusion

The physical education teachers evaluated reported vocal complaints that affected their function and it is suggested to be related with the cardiac autonomic regulation.

Vocal indices of stress: a review

OBJECTIVE

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.

STUDY DESIGN

Literature review, discussion of results, and direction for further study.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Interactions between voice fundamental frequency and cardiovascular parameters. Preliminary results and physiological mechanisms

OBJECTIVES

To determine heart rate influence on voice fundamental frequency under stress conditions.

METHODS

In 14 healthy volunteers, heart rate and blood pressure variables were analyzed during three classical autonomic tasks. Sustained voice samples were obtained to analyze F0.

RESULTS

Cold pressure test increased mean blood pressure, without effect on heart rate; isometric and mental tasks increased heart rate and blood pressure. Voice F0 was only affected by mental and cold ice tasks; it significantly correlated with the heart rate that occurred before and during every vocal emission.

DISCUSSION

Cardiovascular changes showed that subjects were significantly stressed during autonomic tasks. Heartbeat variations had a regular and significant influence on phonatory frequency, and this effect occurred during baseline and stress conditions.