Anne-Maria Laukkanen

Acoustic impedance of an artificially lengthened and constricted vocal tract

Voice training techniques often make use of exercises involving partial occlusion of the vocal tract, typically at the anterior part of the oral cavity or at the lips. In this study two techniques are investigated: a bilabial fricative and a small diameter hard-walled tube placed between the lips. Because the input acoustic impedance of the vocal tract is known to affect both the shaping of the glottal flow pulse and the vibrational pattern of the vocal folds, a study of the input impedance is an essential step in understanding the benefits of these two techniques. The input acoustic impedance of the vocal tract was investigated theoretically for cases of a vowel, bilabial occlusion (fully closed lips), a bilabial fricative, and artificially lengthening the tract with small diameter tubes. The results indicate that the tubes increase the input impedance in the range of the fundamental frequency of phonation by lowering the first formant frequency to nearly that of the bilabial occlusion (the lower bound on the first formant) while still allowing a continuous airflow. The bilabial fricative also has the effect of lowering the first formant frequency and increasing the low-frequency impedance, but not as effectively as the extension tubes.

Vocal Tract and Glottal Function During and After Vocal Exercising With Resonance Tube and Straw

OBJECTIVE The present study aimed to investigate the vocal tract and glottal function during and after phonation into a tube and a stirring straw. METHODS A male classically trained singer was assessed. Computerized tomography (CT) was performed when the subject produced [a:] at comfortable speaking pitch, phonated into the resonance tube and when repeating [a:] after the exercise. Similar procedure was performed with a narrow straw after 15 minutes silence. Anatomic distances and area measures were obtained from CT midsagittal and transversal images. Acoustic, perceptual, electroglottographic (EGG), and subglottic pressure measures were also obtained. RESULTS During and after phonation into the tube or straw, the velum closed the nasal passage better, the larynx position lowered, and hypopharynx area widened. Moreover, the ratio between the inlet of the lower pharynx and the outlet of the epilaryngeal tube became larger during and after tube/straw phonation. Acoustic results revealed a stronger spectral prominence in the singer/speakers formant cluster region after exercising. Listening test demonstrated better voice quality after straw/tube than before. Contact quotient derived from EGG decreased during both tube and straw and remained lower after exercising. Subglottic pressure increased during straw and remained somewhat higher after it. CONCLUSION CT and acoustic results indicated that vocal exercises with increased vocal tract impedance lead to increased vocal efficiency and economy. One of the major changes was the more prominent singers/speakers formant cluster. Vocal tract and glottal modifications were more prominent during and after straw exercising compared with tube phonation.

Effects of voice training and voice hygiene education on acoustic and perceptual speech parameters and self-reported vocal well-being in female teachers

Voice education programs may help in optimizing teachers’ voice use. This study compared effects of voice training (VT) and voice hygiene lecture (VHL) in 60 randomly assigned female teachers. All 60 attended the lecture, and 30 completed a short training course in addition. Text reading was recorded in working environments and analyzed for fundamental frequency (F0), equivalent sound level (Leq), alpha ratio, jitter, shimmer, and perceptual quality. Self-reports of vocal well-being were registered. In the VHL group, increased F0 and difficulty of phonation and in the VT group decreased perturbation, increased alpha ratio, easier phonation, and improved perceptual and self-reported voice quality were found. Both groups equally self-reported increase of voice care knowledge. Results seem to indicate improved vocal well-being after training.

Effects of a Semioccluded Vocal Tract on Laryngeal Muscle Activity and Glottal Adduction in a Single Female Subject

Voice training exploits semiocclusives, which increase vocal tract interaction with the source. Modeling results suggest that vocal economy (maximum flow declination rate divided by maximum area declination rate, MADR) is improved by matching the glottal and vocal tract impedances. Changes in MADR may be correlated with thyroarytenoid (TA) muscle activity. Here the effects of impedance matching are studied for laryngeal muscle activity and glottal resistance. One female repeated [pa:p:a] before and immediately after (a) phonation into different-sized tubes and (b) voiced bilabial fricative [β:]. To allow estimation of subglottic pressure from the oral pressure, [p] was inserted also in the repetitions of the semiocclusions. Airflow was registered using a flow mask. EMG was registered from TA, cricothyroid (CT) and lateral cricoarytenoid (LCA) muscles. Phonation was simulated using a 7 × 5 × 5 point-mass model of the vocal folds, allowing inputs of simulated laryngeal muscle activation. The variables were TA, CT and LCA activities. Increased vocal tract impedance caused the subject to raise TA activity compared to CT and LCA activities. Computer simulation showed that higher glottal economy and efficiency (oral radiated power divided by aerodynamic power) were obtained with a higher TA/CT ratio when LCA activity was tuned for ideal adduction.

Vocal tract changes caused by phonation into a tube: a case study using computer tomography and finite-element modeling.

Phonation into a glass tube is a voice training and therapy method that leads to beneficial effects in voice production. It has not been known, however, what changes occur in the vocal tract during and after the phonation into a tube. This pilot study examined the vocal tract shape in a female subject before, during, and after phonation into a tube using computer tomography (CT). Three-dimensional finite-element models (FEMs) of the vocal tract were derived from the CT images and used to study changes in vocal tract input impedance. When phonating on vowel [a:] the data showed tightened velopharyngeal closure and enlarged cross-sectional areas of the oropharyngeal and oral cavities during and after the tube-phonation. FEM calculations revealed an increased input inertance of the vocal tract and an increased acoustic energy radiated out of the vocal tract after the tube-phonation. The results indicate that the phonation into a tube causes changes in the vocal tract which remain also when the tube is removed. These effects may help improving voice production in patients and voice professionals.

Can vocal economy in phonation be increased with an artificially lengthened vocal tract? A computer modeling study

Voiced obstruents and phonation into tubes are widely used as vocal exercises. They increase the inertive reactance of the vocal tract in the 200–1000 Hz range and thereby reinforce vocal fold vibration. But the effect is strong only when the epilarynx tube is also narrowed. The present study focused on the effects of a ‘resonance tube’ (27 cm in length, 0.5 cm2 cross-sectional area, hard walls) on vocal tract reactance and the accompanying economy of voice production (defined as maximum flow declination rate (MFDR), divided by maximum area declination rate (MADR)). The vowel /u/ and phonation into the tube were simulated with a computer model. Three values were given to the cross-sectional area of the epilarynx tube (0.2 cm2, 0.5 cm2, and 1.6 cm2), which is at the opposite end of the vocal tract from the artificial ‘resonance tube’. The degree of glottal adduction was varied in order to find the economy maximum for each epilarynx tube setting. Results showed that the ‘resonance tube’ lowered F1 from 300 Hz to 150 Hz and doubled the vocal tract inertive reactance at F0=100 Hz. The largest economy with the ‘resonance tube’ was obtained when the epilarynx tube was narrowed (relative to the rest of the vocal tract) and sufficiently tight adduction was used. Most importantly, the intraoral acoustic pressure (calculated at 0.8 cm behind the lips) was tripled with the tube. The results suggest that by optimizing the vibratory sensations in the face that are attributed to increased intraoral acoustic pressure, phonation into a tube may assist a trainee in finding an optimal glottal and epilaryngeal setting for the greatest vocal economy.

A physiological and acoustic study on voiced bilabial fricative /β:/ as a vocal exercise

The voiced bilabial fricative/beta:/has been used as a vocal exercise. The present study investigated the effects of the exercise on voice production and voice source. This study compared vowel phonation on the syllable /a:p/ with the production of the exercise and vowel phonation before and immediately after the exercise. The methods were (a) dual-channel electroglottography, from which the vertical laryngeal position was derived, (b) electromyography using surface electrodes, and (c) inverse filtering of the acoustic signal to obtain an estimate of the voice source. In the production of /beta:/ as compared with vowel phonation in most of the cases, the vertical laryngeal position seemed to be higher, the muscular activity of the larynx lower, and the slope of the voice source spectrum steeper. In vowel phonation after the exercise, the muscular activity seemed to be lower in most cases, although the voice source remained unchanged. This seems to indicate improved vocal economy.

Changes in Teachers’ Speech during a Working Day with and without Electric Sound Amplification

An increase in fundamental frequency (F₀) and in sound pressure level (SPL) has been reported both after vocal loading tests and after a teacher’s working day. This increase has been found to be greater among teachers with fewer voice complaints. The present study investigated speech changes during a teacher’s working day (a) in ordinary conditions and (b) when using electric sound amplification while teaching. Five Icelandic teachers (mean age 51 years) volunteered as subjects. Classroom speech was recorded with a portable DAT recorder and a head-mounted microphone first in ordinary conditions, and the next week while using electrical sound amplification. Recordings were made during the first and the last lesson of the hardest working day of the week. F₀ and SPL were analyzed. The subjects’ comments were gathered by questionnaire. An increase in F₀ and SPL was found during the working day in both teaching conditions but the change was larger and for F₀ statistically significant when amplification was used. All 5 teachers reported less tiredness of the vocal mechanism when using amplification. The results support the suggestion that a vocal loading-related increase in F₀ and SPL is not merely a sign of vocal fatigue but may even reflect an adequate adaptation to loading. Situational factors cannot be ignored, however.

On the perception of emotions in speech: the role of voice quality

This experiment studied the role of voice quality in the communication of emotions in speech. The material was derived from an earlier study. There three subjects produced a three-word utterance expressing different emotional states. The glottal airflow waveform was estimated from the acoustic speech pressure signal using an inverse filtering technique.In the present study the differences in F0 level and the intrasyllabic F0 changes were artificially eliminated and only the first 200 ms of the primarily stressed syllable replayed at equal sound volume to the listeners (10 in total). The listeners tended to categorize the samples to represent emotions implying either high or low psychophysiological activity level. This seemed to emanate from signs of vocal effort level. Perception of vocal effort was significantly related to the glottal source type and F1.Decision of valence of the perceived emotion was in this material significantly related to F1 and F4. The type of glottal source, however, may also contr...

Vocal Loading-Related Changes in Male Teachers’ Voices Investigated before and after a Working Day

Vocal loading-related changes have mainly been investigated in female voice users. The present study investigated male teachers’ voices before and after a working day. A questionnaire was used to select 22 male teachers as subjects from a larger group. Ten reported suffering often from symptoms of vocal fatigue (MC = multiple complaints group), 12 reported few vocal complaints (FC group). The subjects recorded a text reading sample at habitual loudness and loudly, and sustained vowel [a:] before and after an approximately 6-hour working day. Text samples were analyzed for total sound pressure level (SPL) and SPL at three frequency regions (50–1,000 Hz, 1–2 kHz, 2–5 kHz), fundamental frequency (F0) and alpha ratio [(SPL 1–5 kHz) – SPL (50 Hz–1 kHz)]. Jitter and shimmer were calculated from the vowel. The subjects filled in a questionnaire about vocal sensations. The MC group reported more symptoms of vocal fatigue, and the symptoms increased during the working day. F0 and SPL increased in both groups. Alpha ratio increased in the MC group but remained the same in the FC group. The MC group had higher values of jitter and shimmer. Jitter diminished in the FC group but did not change significantly in the MC group. The differences between the groups reflect either different strategies for coping with vocal loading or different loading-induced changes in the vocal organ.