Experimental and Computational Modeling of the Effects of Voice Therapy Using Tubes.

Purpose Phonations into a tube with the distal end either in the air or submerged in water are used for voice therapy. This study explores the effective mechanisms of these therapy methods. Method The study applied a physical model complemented by calculations from a computational model, and the results were compared to those that have been reported for humans. The effects of tube phonation on vocal tract resonances and oral pressure variation were studied. The relationships of transglottic pressure variation in time Ptrans ( t) versus glottal area variation in time GA( t) were constructed. Results The physical model revealed that, for the phonation on [u:] vowel through a glass resonance tube ending in the air, the 1st formant frequency ( F1 ) decreased by 67%, from 315 Hz to 105 Hz, thus slightly above the fundamental frequency ( F0 ) that was set to 90-94 Hz . For phonation through the tube into water, F1 decreased by 91%-92%, reaching 26-28 Hz, and the water bubbling frequency Fb ≅ 19-24 Hz was just below F1 . The relationships of Ptrans ( t) versus GA( t) clearly differentiate vowel phonation from both therapy methods, and show a physical background for voice therapy with tubes. It is shown that comparable results have been measured in humans during tube therapy. For the tube in air, F1 descends closer to F0 , whereas for the tube in water, the frequency Fb occurs close to the acoustic-mechanical resonance of the human vocal tract. Conclusion In both therapy methods, part of the airflow energy required for phonation is substituted by the acoustic energy utilizing the 1st acoustic resonance. Thus, less flow energy is needed for vocal fold vibration, which results in improved vocal efficiency. The effect can be stronger in water resistance therapy if the frequency Fb approaches the acoustic-mechanical resonance of the vocal tract, while simultaneously F0 is voluntarily changed close to F1.

Subjective evaluation of voice and working conditions and phoniatric examination in kindergarten teachers.

AIMS: This study evaluated the prevalence of voice problems in kindergarten teachers and investigated some background factors affecting vocal health. METHODS: One hundred and nineteen female kindergarten teachers volunteered by responding to an Internet questionnaire on voice habits, voice symptoms, and the amount of negative impact various working conditions may have on their voices. Phoniatric examination was carried out with a rigid laryngoscope. RESULTS: Of the subjects, 71.5% reported frequent strain on the voice (monthly or more often), and 56.3% reported hoarseness without infection. Eighty-six percent reported that when their voice got tired during the working day it recovered quite well, well or remarkably well by the next day. Noise at work was considered most detrimental to the voice. Clear organic findings were observed in 10.9% of the cases and did not correlate with subjective voice symptoms. CONCLUSIONS: The results confirmed earlier findings that a remarkable number of kindergarten teachers suffer from voice problems and consider noise in the environment especially to be harmful to their voices. However, the majority reported recovering well from vocal symptoms. Further studies are needed on individual speech habits, working day-related voice evaluation, recovery time and work-environmental factors. A follow-up is warranted to identify the main factors leading to voice problems.

Evaluation of support in singing.

This study searched for perceptual, acoustic, and physiological correlates of support in singing. Seven trained professional singers (four women and three men) sang repetitions of the syllable [pa:] at varying pitch and sound levels (1) habitually (with support) and (2) simulating singing without support. Estimate of subglottic pressure was obtained from oral pressure during [p]. Vocal fold vibration was registered with dual-channel electroglottography. Acoustic analyses were made on the recorded samples. All samples were also evaluated by the singers and other listeners, who were trained singers, singing students, and voice specialists without singing education (a total of 63 listeners). We rated both the overall voice quality and the amount of support. According to the results, it seemed impossible to observe any auditory differences between supported singing and good singing voice quality. The acoustic and physiological correlates of good voice quality in absolute values seem to be gender and task dependent, whereas the relative optimum seems to be reached at intermediate parameter values.

Effects of amplified and damped auditory feedback on vocal characteristics.

This study tested two possible methods for reducing vocal load e.g. during classroom speech. Six female subjects read aloud from a text (1) under normal circumstances, (2) while hearing their own voice amplified (through headphones) and (3) with auditory feedback damped by foam plastic earplugs inserted in the outer ear canal. Fundamental frequency (F0) and sound pressure level (SPL) decreased during both amplified and damped feedback. Additionally, during amplification the relative level of F0 compared to that of the first formant diminished, likewise the alpha ratio. These changes may indicate reduced vocal fold adduction. The results suggest that both amplification and damping of auditory feedback may reduce vocal load during phonation.

Effects of sound amplification on teachers' speech while teaching.

Voice problems are common among teachers. This is most likely due to the heavy vocal load of their profession. The present study investigated one possible method to decrease the vocal load. The effects of amplification on classroom speech were studied on five Icelandic teachers (three females, two males, mean age 51 years). Classroom speech was recorded with a portable DAT recorder and a head-mounted microphone, first under ordinary conditions and in the next week while using electrical sound amplification. The average fundamental frequency (F0), sound pressure level (SPL) and phonation time were measured. According to the results, amplification significantly lowered both F0 (average 8.6 Hz for the females and 11.3 Hz for the males, p = 0.002 and 0.0001, respectively) and SPL (about 1 dB for both genders, p < 0.05), while phonation time was not significantly affected. The results suggest that electric amplification is likely to reduce vocal load.

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.

The external frame function in the control of pitch, register, and singing mode: radiographic observations of a female singer.

This study investigates pitch control, register, and singing mode related movements of the laryngo-pharyngeal structures by radiographic methods. One trained female singer served as the subject. The results show that singing voice production involves complex movements in the laryngeal structures. Pitch related increase in the thyro-arytenoid distance (vocal fold length) is nonlinear, slowing down as pitch rises. Similar observations have been made earlier. At the highest pitches, a shortening of the distance can be seen, suggesting the use of alternative pitch control mechanisms. The various observations made support the existence of three registers in this trained female singing voice. Open and covered modes of singing seemed to be distinguishable on the basis of different amounts of inner and outer forces acting on the larynx. Therefore, caution must be exercised when generalizing from the results.

Simultaneous videofluorographic and dual-channel electroglottographic registration of the vertical laryngeal position in various phonatory tasks.

Simultaneous tracking of the vertical laryngeal position in various phonatory tasks was performed for 2 subjects (one male, one female) using dual-channel electroglottography (EGG) and videofluorography (videofluoroscopy). The tasks included phonation on [a:] with voluntary repeated (1) heightening and (2) lowering of the laryngeal position; alternation between [a:] and phonation on (3) [b], (4) [m], and (5) the voiced bilabial fricative [beta:]; and (6) production of the corner vowels [a, i, u]. EGG and videofluorography agreed about the direction of changes in the vertical laryngeal position in most cases. Most disagreements were found in the amount of changes. Reasons for the discrepancies, including, for example, changes in the resting position of the larynx and anteroposterior movements of the cartilages, are discussed. It can be concluded that dual-channel EGG is a valuable clinical and pedagogical tool for the analysis of the vertical displacement of larynx in well-specified phonatory tasks. The method should act most reliably on separately phonated vowels. Its applicability for studying laryngeal biomechanics more wholistically, however, is limited.

Parameterization of the voice source by combining spectral decay and amplitude features of the glottal flow.

A new method is presented for the parameterization of glottal volume velocity waveforms that have been estimated by inverse filtering acoustic speech pressure signals. The new technique, Parameter for Spectral and Amplitude Features of the Glottal Flow (PSA), combines two features of voice production, the AC value and the spectral decay of the glottal flow, both of which contribute to changes in vocal loudness. PSA yields a single parameter that characterizes the glottal flow in different loudness conditions. By analyzing voices of 8 speakers it was shown that the new parameter correlates strongly with the sound pressure level of speech.

A physiological and acoustic study on voiced bilabial fricative/beta:/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.

Vocal-fold collision mass as a differentiator between registers in the low-pitch range.

Register shift between the chest and falsetto register is generally studied in the higher-than-speaking pitch range. However, a similar difference can also be produced at speaking pitch level. The shift from breathy "falsetto" phonation to normal chest voice phonation was studied in normal female (pitch range 170-180 Hz) and male (pitch range 94-110 Hz) subjects. The phonations gliding from falsetto to normal chest voice were analyzed using iterative adaptive inverse filtering and electroglottography. Both trained and untrained, as well as female and male subjects, were able to produce an abrupt register shift from soft falsetto to soft chest register phonation. The differences between male and female speakers in the glottal flow waveforms were smaller than expected. The register shift is interpreted in terms of a "critical mass" concept of chest register phonation.

On the effects of various vocal training methods on glottal resistance and efficiency. A preliminary report.

The glottal resistance, i.e. the ratio of subglottic pressure to glottal flow, and the laryngeal efficiency, i.e. the ratio of oral acoustic power to aerodynamic subglottal power (multiplication of subglottig pressure and glottal flow), were measured for 11 subjects (3 males) with normal voices and for 1 female patient with glottal insufficiency in the repeated production of the nonsense word /paappa/ immediately before and after 1 min of vocal exercising with /beta:, m:/ and phonation into a narrow glass tube. For the subjects with normal voices the glottal resistance decreased in most cases and the laryngeal efficiency in half of the cases due to increased glottal flow. In contrast, for the patient the glottal resistance and efficiency increased due to decreased glottal flow. The results suggest that the vocal exercises instantly affected the control of the glottal width.

Phonation into a tube as a voice training method: acoustic and physiologic observations.

Phonation into narrow glass tubes has been used as a voice training method. The present study examined phonatory and voice quality during and after tube phonation. The methods used were (a) electromyography with surface electrodes, (b) a dual-channel electroglottography from which the vertical larynx position was derived and (c) inverse filtering of the acoustic signal of vowel samples produced before and immediately after the exercise. Phonation into a tube seemed to cause a tendency to heighten the vertical laryngeal position. For female subjects (n = 3) the tube exercise tended to lead to increased vocal effort in vowel production after the exercise and, in contrast, to a tendency for a more relaxed voice production for the males (n = 2).

Artificial pitch changing in auditory feedback as a possible method in voice training and therapy.

This study tested the effects of artificial pitch change of the auditory feedback on the fundamental frequency of normal-hearing subjects in text reading. The subjects (4 males, 24 females; 4 subjects were professional speech trainers, 3 subjects were trained singers; 1 male and 6 females were habitually using a non-optimal speaking pitch) read aloud from a text first the same paragraph twice in normal circumstances and then again while hearing their own voices, in real time changed in pitch, through headphones. In most cases the reading pitch increased during auditory feedback manipulations and the changes were larger than the differences found between recapitulations of the same text. The speech trainers and singers did not differ from the other subjects in their reactions. Three of the 7 subjects with pitch problems did not change the pitch at all and 3 did change it to an inappropriate direction. Only 1 subject with a pitch problem did benefit from the feedback manipulation. These results suggest that with certain limitations this method could be taken advantage of in voice training.