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.     

Vocal Improvement After Voice Therapy in Unilateral Vocal Fold Paralysis

Unilateral vocal fold paralysis (UVFP) is associated with changes in acoustic and aerodynamic voice measurements and can have a significant impact on a patient's quality of life. Few objective data regarding the efficacy of voice therapy for UVFP exist. The aim of this study was to retrospectively analyze voice modifications in a group of patients with UVFP before and after voice therapy. Forty patients with UVFP of different etiology were included in the study. Each subject had voice therapy with an experienced speech/language pathologist twice a week; the mean number of sessions was 12.6. A multidimensional assessment protocol was used; it included videoendoscopy, the maximum phonation time (MPT), the GIRBAS scale, spectrograms and a perturbation analysis, and the Voice Handicap Index (VHI). Pre- and posttreatment data were compared by means of the Wilcoxon and Student's t tests. A complete glottal closure was seen in 8 patients before voice therapy and in 14 afterward. Mean MPT increased significantly. In the perceptual assessment, the difference was significant for five out of six parameters. A significant improvement was found on spectrographic analysis; as for perturbation analysis, the differences in jitter, shimmer, and noise-to-harmonic ratio values were significant. VHI values showed a clear and significant improvement. A significant improvement of voice quality and quality of life after voice therapy is an often reached and reasonable goal in patients with UVFP.     

Effect of Hydration and Vocal Rest on the Vocal Fatigue in Amateur Karaoke Singers

Karaoke singing is a very popular entertainment among young people in Asia. It is a leisure singing activity with the singer's voice amplified with special acoustic effects in the backdrop of music. Music video and song captions are shown on television screen to remind the singers during singing. It is not uncommon to find participants singing continuously for four to five hours each time. As most of the karaoke singers have no formal training in singing, these amateur singers are more vulnerable to developing voice problems under these intensive singing activities. This study reports the performance of 20 young amateur singers (10 males and 10 females, aged between 20-25 years) on a series of phonatory function tasks carried out during continuous karaoke singing. Half of the singers were given water to drink and short duration of vocal rests at regular intervals during singing and the other half sang continuously without taking any water or rest. The subjects who were given hydration and vocal rests sang significantly longer than those who did not take any water or rest. The voice quality, as measured by perceptual and acoustic measures, and vocal function, as measured by phonetogram, did not show any significant changes during singing in the subjects who were given water and rest during the singing. However, subjects who sang continuously without drinking water and taking rests showed significant changes in the jitter measure and the highest pitch they could produce during singing. These results suggest that hydration and vocal rests are useful strategies to preserve voice function and quality during karaoke singing. This information is useful educational information for karaoke singers.     

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.     

Vocal intensity in speakers and singers.

Vocal intensity is studied as a function of fundamental frequency and lung pressure. A combination of analytical and empirical models is used to predict sound pressure levels from glottal waveforms of five professional tenors and twenty five normal control subjects. The glottal waveforms were obtained by inverse filtering the mouth flow. Empirical models describe features of the glottal flow waveform (peak flow, peak flow derivative, open quotient, and speed quotient) in terms of lung pressure and phonation threshold pressure, a key variable that incorporates the Fo dependence of many of the features of the glottal flow. The analytical model describes the contributions to sound pressure levels SPL by the vocal tract. Results show that SPL increases with Fo at a rate of 8-9 dB/octave provided that lung pressure is raised proportional to phonation threshold pressure. The SPL also increases at a rate of 8-9 dB per doubling of excess pressure over threshold, a new quantity that assumes considerable importance in vocal intensity calculations. For the same excess pressure over threshold, the professional tenors produced 10-12 dB greater intensity than the male nonsingers, primarily because their peak airflow was much higher for the same pressure. A simple set of rules is devised for predicting SPL from source waveforms.     

Vocal fold exposure in phonosurgery

A difficult laryngeal exposure is made easier by placement of the patient's head and neck into the Boyce-Jackson “sniffing position” and then flexing them further if necessary, by selection of a laryngoscope appropriate to the patient and to the triangular glottic shape, by placement of the laryngoscope along the path of least resistance, by use of a true suspension device in order to apply the force for laryngoscopy towards the larynx and away from the teeth and gums, and by allowing time for the force to work. With these techniques, an easy exposure is made almost perfect. The true vocal folds are exposed from vocal process to anterior commissure without the need for external pressure, the endotracheal tube remains out of sight between the arytenoids, and there is no risk to the teeth, gums, and cervical spine.     

Vocal tremor and psychological stress

This study examines vocal tremor and its decrease in high versus low experimentally induced stress situations. We have analyzed the Amplitude Tremor Intensity Index (ATRI) and Frequency Tremor Intensity Index (FTRI) from the prolongation of vowel /a/ for approximately 5 seconds, under baseline conditions and under 3 different test conditions (reading of tongue twister, reading of tongue twister with delayed auditory feedback [DAF], and spelling of alphabet in reverse order), in a 2-test series, with and without demanding experimental instructions (Experiments 1 and 2, respectively). Inclusion of experimental instructions was considered as making the first test situation more stressful than the second one. Our results show a significant decrease in the ATRI variable when reading a tongue twister with DAF in relation to the baseline for the first test but not in the second, which suggests a suppression or significant reduction of amplitude tremor only in high-stress situations.     

Vocal fold microsurgery in singers

Some singers with benign vocal fold mucosal lesions remain unacceptably impaired vocally in spite of compliance with a regimen of medical treatment and voice therapy lasting several months—or even years. I present here my experience with 62 singers who, because of this predicament, chose to undergo vocal fold microsurgery. This series is the second largest reported to date in English literature. Procedures are presented which were used for patient selection, education, and vocal retraining, as well as for surgery itself and postoperative care. Results reported here include (a) comparison of my auditory-perceptual ratings of singing voice impairment before and after surgery, (b) preoperative versus postoperative videostroboscopic findings, (c) postoperative rate of return to public singing, and (d) postoperative patient questionnaires which sought to uncover patient/singer perceptions of the results of vocal fold surgery. Excellent results were achieved overall with a very low incidence of untoward results, and no complications were encountered.