Effects of Vocal Constitution and Autonomic Stress-Related Reactivity on Vocal Endurance in Female Student Teachers

Several studies revealed a high percentage of voice problems in future teachers. The influence of vocal constitution on the vocal endurance is, however, still unclear. The goal of this study was to evaluate whether the increase of voice fundamental frequency (F0) during teaching is caused by (1) autonomic regulation patterns under stress, (2) anxiety as an emotional factor, or (3) limitations in voice constitution. Thirty-three subjects with either normal voice constitution (n = 15, group 1) or constitutional hypofunction (n = 18, group 2) assessed by voice range profile measurements were enrolled in this study. Furthermore, they underwent a standardized baseline test to register selected autonomic test parameters and were classified into autonomic outlet types (AOT) as proposed by Johannes et al. Later the subjects were examined during 1 hour of teaching (field study). The parameters tested included heart rate, pulse transition time, finger temperature, and voice fundamental frequency. To measure situational anxiety and general anxiety proneness, a state-trait anxiety inventory was taken. Eleven subjects per group were identified as autonomic stable (AOT 1), two per group as responding cardiovascularly (AOT 2), and two of group 1 and four of group 2, respectively, as having higher heart rate and higher blood pressure responses to stress (AOT 4). One subject had to be excluded because of missing data. However, statistical analyses showed no differences between AOT groups regarding the voice constitution groups. Increased fundamental frequencies of speaking voice after 30 and 45 minutes of teaching were found in group 2 (constitutional hypofunction). No effect of state or trait anxiety on voice endurance could be detected. Thus, the increase of fundamental frequency of voice has to be regarded as a consequence of vocal fatigue. A constitutionally weak voice seems to be a risk factor for developing a professional voice disorder.     

Acoustic Measures and Self-reports of Vocal Fatigue by Female Teachers

This study investigated the relation of symptoms of vocal fatigue to acoustic variables reflecting type of voice production and the effects of vocal loading. Seventy-nine female primary school teachers volunteered as subjects. Before and after a working day, (1) a 1-minute text reading sample was recorded at habitual loudness and loudly (as in large classroom), (2) a prolonged phonation on [a:] was recorded at habitual speaking pitch and loudness, and (3) a questionnaire about voice quality, ease, or difficulty of phonation and tiredness of throat was completed. The samples were analyzed for average fundamental frequency (F0), sound pressure level (SPL), and phonation type reflecting alpha ratio (SPL [1-5 kHz]-SPL [50 Hz-1 kHz]). The vowel samples were additionally analyzed for perturbation (jitter and shimmer). After a working day, F0, SPL, and alpha ratio were higher, jitter and shimmer values were lower, and more tiredness of throat was reported. The average levels of the acoustic parameters did not correlate with the symptoms. Increase in jitter and mean F0 in loud reading correlated with tiredness of throat. The results seem to suggest that, at least among experienced vocal professionals, voice production type had little relevance from the point of view of vocal fatigue reported. Differences in the acoustic parameters after a vocally loading working day mainly seem to reflect increased muscle activity as a consequence of vocal loading.     

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

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.     

MRI Anatomical and Morphological Differences in the Vocal Tract Between Dysphonic and Normal Adult Women

Objective

To analyze the vocal tract morphometry of women with vocal nodules (VN) compared with normal subjects by means of magnetic resonance imaging (MRI) at rest position.

Study Design

Prospective study.

Methods

The present research included 20 young adult women, aged 18–40 years: 10 dysphonic patients with VN and 10 normal subjects. All participants were tested using MRI; 12 measurements of the vocal tract were performed: nine in median sagittal section and three in axial section.

Results

The 12 measurements were smaller in the dysphonic group; statistical significance was obtained for three parameters: in the sagittal plane, the laryngeal vestibule area was significantly smaller in the dysphonic group, with P = 0.012∗ (∗ = statistical significance); in the axial section, the distance between the right and left vocal processes of the arytenoids’ cartilages and the distance between the anterior commissure of the glottis and the laryngeal posterior wall were also significantly lower in the dysphonic group, with P = 0.036∗ and 0.010∗, respectively. Significant differences in the vocal tract morphometry of individuals with VN were observed compared with normal subjects, at rest position.

Conclusions

Results obtained from this study suggest that patients with VN may present a constantly increased tension of the laryngeal muscles, even at rest; moreover, reduced anterior-posterior dimension of the larynx may be a morphological characteristic of patients with VN.