Adjustment of Vocal Tract Shape via Biofeedback: Influence on Vowels

Volitional and Non-volitional Devices Used in Voice Therapy and Training: A Scoping Review-Part A

OBJECTIVE

To map the volitional and non-volitional devices used by speech and language pathologists (SLPs) in voice training and therapy and characterize their use in research on voice interventions.

METHODS

This scoping review is the first part of a larger study. The electronic search was carried out by mapping the references in PubMed/Medline, LILACS/BVS, Scopus, Web of Science, EMBASE, and the Cochrane Library, and the manual search was carried out in the grey literature. Two blind independent reviewers selected and extracted data; divergences were solved by consensus. The data extracted in this part of the study were the authorship and year of publication, country, study design, sample characteristics, intervention modality, ingredient, target, mechanism of action, dosage, and outcome measures. They were addressed with descriptive analysis.

RESULTS

Publications that use devices as ingredients are mostly from the last two decades, mainly carried out in the United States of America and Brazil, in adults of both sexes with behavioral dysphonia. Forty-two types of devices were used, many of them with similar approaches but different nomenclatures. Most devices were used voluntarily, focusing on vocal function, and aiming to increase source and filter interaction. Most studies used silicone tubes. The most reported technical specification to apply the ingredient was surface electrodes on the neck. Device dosage was time-controlled, and the most used outcomes were self-assessment and acoustic analysis.

CONCLUSION

Devices are currently used as ingredients in vocal interventions, with a greater focus on increasing the source and filter interaction, associated with silicone tubes (the most used devices in these studies), which have been dosed with performance time. Outcomes were measured with self-assessment instruments.

Relationship Between Oropharyngeal Geometry and Acoustic Parameters in Singers: A Preliminary Study

OBJECTIVE

To verify possible correlations between formant and cepstral parameters and oropharyngeal geometry in singers, stratified by sex.

METHOD

Voice records and oropharyngeal measures of 31 singers - 13 females and 18 males, mean age of 28 (±5.0) years - were retrieved from a database and analyzed. The oropharyngeal geometry measures were collected with acoustic pharyngometry, and the voice records consisted of sustained vowel /Ԑ/ phonation, which were exported to Praat software and edited to obtain the formant and cepstral parameters, stratified by sex. The Pearson linear correlation test was applied to relate voice parameters to oropharyngeal geometry, at the 5% significance level; the linear regression test was used to justify the variable related to the second formant.

RESULTS

Differences between the sexes were identified only in the oral cavity length (greater in males) and pharyngeal cavity length (greater in females). There was a linear correlation between the third formant and the cepstrum in the female group. In the male group, there was a linear correlation between the cepstrum and the third and fourth formants. A positive linear correlation with up to 95% confidence was also identified between the pharyngeal cavity volume and the second formant in the female group, making it possible to estimate a regression model for the second formant (R2 = 0.70).

CONCLUSION

There are correlations between the oropharyngeal geometry and formant and cepstral parameters in relation to sex. The pharyngeal cavity volume showed the greatest correlation between females and the second formant.

Vocal Tract and Subglottal Impedance in High Performance Singing: A Case Study

OBJECTIVES/HYPOTHESIS

The respiratory process is important in vocal training and in professional singing, the airflow is highly important. It is hypothesized that subglottal resonances are important to the singing voice in high performance singing.

STUDY DESIGN

Single subject, prospective.

METHOD

A professional soprano singer shaped her vocal tract to form the vowels [a], [e], [i], [o], and [u] at the pitch d4. We measured phonated vowels and the vocal tract impedance spectra with a deterministic noise supplied by an iPhone buzzer in the range of 200 to 4,000 Hz at closed glottis, during exhalation and during inhalation while maintaining the shape of the vocal tract.

RESULTS

Measurements of the phonated vowels before and after the different glottal adjustments were highly reproducible. Vocal tract resonances and the ones resulting during respiration are reported. The impedance spectra show vowel dependent resonances with closed and open glottis. The formants of the vocal spectra are explained by including both, the vocal tract, and the subglottal resonances.

CONCLUSION

The findings indicate that subglottal resonances influence the first formant as well as the singers's formant cluster in high-performance singing. The instrumental setup used for the impedance measurement allows a simple and lightweight procedure for a measurement of vocal tract and subglottal resonances.

Acoustically Induced Vocal Training for Individuals With Impaired Hearing

OBJECTIVES/HYPOTHESIS

Articulation, phonation, and resonance disorders in the speech of hearing-impaired-speakers reduces intelligibility. The study focusses on (1) whether nonacoustic feedback may facilitate the adjustment of the vocal tract, leading to increased vocal tract resonance, and (2) whether training with the feedback would be helpful for the subsequent formation of vowels.

STUDY DESIGN

Prospective.

METHODS

Seven profoundly hearing-impaired participants used acoustic sound waves in the frequency range of the first two vocal tract resonances applied in front of the open mouth at intensities above 1 Pa. They were asked to amplify the sound via adjusting the vocal tract. The sound waves corresponded to the first and second resonance frequencies of the vowels [u], [o], and [a]. The self-assessment of the participants and a software-based/auditory analysis was reported.

RESULTS

The participants were able to enhance the acoustic signal by adjusting the vocal tract shape. The self-perception of the participants, the auditory voice analysis, and the acoustic analysis of vowels were consistent with each other. While the maximum sound pressure levels were constant, the mean sound pressure levels increased. Breathiness and hoarseness declined during the exercises. Resonance/harmonic-to-noise ratio increased, especially for the vowels [u], [o], [a]. Furthermore, the positively connoted feedback from the participants indicated easier sound production.

CONCLUSION

Nonauditory feedback, based on acoustic waves, could be suitable for improving the formation of vowels. The findings are in accordance with a reduction of acoustic losses within the vocal tract.