Physiology and Acoustics of Inspiratory Phonation

Vocal Fold Vibration of the Whistle Register Observed by High-Speed Digital Imaging

INTRODUCTION

Singers use a whistle register to sing at a fundamental frequency above 1000 Hz. In previous studies, vocal fold vibrations with or without complete closure and partial vocal fold vibrations were observed depending on the subject. However, the production mechanism of the whistle register is not yet clearly understood because of the limitations of the imaging device for the glottis and subjects.

OBJECTIVES

This study aims to examine vocal fold vibrations in a whistle register.

METHODS

The dynamic behavior of the glottis was recorded for six singers (four females and two males) using a high-speed digital imaging device with a frame rate above 10,000 fps. Audio signals were recorded simultaneously. The data were analyzed in the form of topography, glottal area waveforms, spectrograms, and phonovibrography to examine spatiotemporal patterns of glottal motion.

RESULTS

The vibratory motion of the vocal folds was classified into six patterns. The first pattern was the entire vocal fold vibration with complete closure during the closed phase. The second to fifth was the entire vocal fold vibration without complete closure, where a gap was observed for the full length of the vocal folds for the second, at the posterior part of the glottis for the third, at the anterior for the fourth, and at both ends for the fifth. In the sixth pattern, the vocal folds vibrated partially. Our results support the previous findings on the vibration of the vocal folds. In addition, we identified novel vibratory patterns in the vocal folds.

CONCLUSION

We conclude that the production of the whistle register is not just an extension of the falsetto register to the higher fundamental-frequency region; rather, the production mechanism of the whistle register appeared to be diverse as a means of vocalization.

High-Speed Videoendoscopic and Acoustic Characteristics of Inspiratory Phonation

PURPOSE

Given the importance of inspiratory phonation for assessment of vocal fold structure, the aim of this investigation was to evaluate and describe the vocal fold vibratory characteristics of inspiratory phonation using high-speed videoendoscopy in healthy volunteers. The study also examined the empirical relationship between cepstral peak prominence (CPP) and glottal area waveform measurements derived from simultaneous high-speed videoendoscopy and audio recordings.

METHOD

Vocally healthy adults (33 women, 28 men) volunteered for this investigation and completed high-speed videoendoscopic assessment of vocal fold function for two trials of an expiratory/inspiratory phonation task at normal pitch and normal loudness. Twelve glottal area waveform measures and acoustic CPP values were extracted for analyses.

RESULTS

Inspiratory phonation resulted in shorter closing time, longer duration of the opening phase, and faster closing phase velocity compared to expiratory phonation. Sex differences were elucidated. CPP changes for inspiratory phonation were predicted by changes in the glottal area index and waveform symmetry index, whereas changes in CPP during expiratory phonation were predicted by changes in asymmetry quotient, glottal area index, and amplitude periodicity.

CONCLUSIONS

Vocal fold vibratory differences were identified for inspiratory phonation when compared to expiratory phonation, the latter of which has been studied more extensively. This investigation provides important basic inspiratory phonation data to better understand laryngeal physiology in vivo and provides a basic model from which to further study inspiratory phonation in a larger population representing a broader age range.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.22223812.

Experimental Study on Inspiratory Phonation Using Physical Model of the Vocal Folds

In inspiratory phonation, the air is inhaled from the mouth. The inhaled air passes through the glottis towards the lungs, thereby inducing the vocal fold vibrations. Such phonation takes place in various situations such as sighs, laughter, and crying. To characterize the inspiratory phonation, an experimental study was carried out using a physical model of the vocal folds. By reversing the direction of the airflow that passed through the vocal fold model, the inspiratory phonation was experimentally realized and compared with the normal expiratory phonation. Our experiments revealed that the phonation threshold pressures as well as the volume flow rates decreased under the inspiratory condition. Accordingly, the vocal efficiency was increased. The fundamental frequency was also increased under the inspiratory condition. The kymograms showed that phase of the upper edge of the vocal fold advanced that of the lower edge under the inspiratory phonation. A mathematical model of the vocal folds was further constructed to elucidate these experiments. Except for few aspects, our experimental findings are in good agreement with the preceding studies on inspiratory phonation (e.g., reversed propagation of the mucosal waves observed in a singer, increased pitches in human subjects, and use of inspiratory phonation in speech therapy).

Measuring Voice Effects of Vibrato-Free and Ingressive Singing: A Study of Phonation Threshold Pressures

BACKGROUND

Phonation threshold pressure (PTP), showing the lowest subglottal pressure producing vocal fold vibration, has been found useful for documenting various effects of phonatory conditions. The need for such documentation is relevant also to the teaching of singing, particularly in view of vocal demands raised in some contemporary as well as early music compositions. The aim of the present study was to test the usefulness of PTP measurement for evaluating phonatory effects of vibrato-free and ingressive singing in professional singers.

METHODS

PTP was measured at a middle, a high and a low pitch in two female and two male singers before and after recording voice range profiles (i) in habitual technique, ie, with vibrato, (ii) in vibrato-free, and (iii) in ingressive phonation. Effects on vocal fold status were examined by videolaryngostroboscopy.

RESULTS

After careful instruction of the singers, no problems were found in applying the PTP method. In some singers videolaryngostroboscopy showed effects after the experiment, eg, in terms of increased mucus and more complete glottal closure. After ingressive phonation PTP increased substantially at high pitch in one singer but changed marginally in the other singers.

CONCLUSION

The method seems useful for assessing and interpreting effects of singing in different styles and as a part of voice diagnostics. Therefore, it seems worthwhile to automatize PTP measurement.

Vocal Tract Morphology in Inhaling Singing: Characteristics During Vowel Production-A Case Study in a Professional Singer

BACKGROUND

A professional singer produced various vowels on a comfortable loudness and pitch in an inspiratory and expiratory phonation manner. The present study investigates the morphological differences and tries to find a link with the acoustical characteristics.

OBJECTIVES/HYPOTHESIS

We hypothesize that features, constantly present over all vowels, characterize inhaling phonation and that the formant frequencies reflect the morphological findings.

STUDY DESIGN

A prospective case study was carried out.

METHODS

A female singer uttered the vowels /a/, /e/, /i/, /o/, and /u/ in a supine position under magnetic resonance imaging, on a comfortable loudness and pitch, in both inhaling and exhaling manner. The exact same parameters as in previous reports were measured (1-3). Acoustical analysis was performed with Praat.

RESULTS

Wilcoxon directional testing demonstrates a statistically significant difference in (1) the distance between the lips, (2) the antero-posterior tongue diameter, (3) the distance between the lips and the tip of the tongue, (4) the distance between the epiglottis and the posterior pharyngeal wall, (5) the narrowing of the subglottic space, and (6) the oropharyngeal and the hypopharyngeal areas. Acoustical analysis reveals slightly more noise and irregularity during reverse phonation. The central frequency of F0 and F1 is identical, whereas that of F2 and F3 increases, and that of F4 varies.

CONCLUSIONS

A smaller mouth opening, a narrowing of the subglottic space, a larger supralaryngeal inlet, and a smaller antero-posterior tongue diameter can be considered as morphological characteristics for reverse phonation. Acoustically, reverse phonation discretely contains more noise and perturbation. The formant frequency distribution concurs with a mouth narrowing and pharyngeal widening during inhaling.

Divergent acoustic properties of gelada and baboon vocalizations and their implications for the evolution of human speech

Human speech has many complex spectral and temporal features traditionally thought to be absent in the vocalizations of other primates. Recent explorations of the vocal capabilities of non-human primates are challenging this view. Here, we continue this trend by exploring the spectro-temporal properties of gelada (Theropithecus gelada) vocalizations. First, we made cross-species comparisons of geladas, chacma baboons, and human vowel space area. We found that adult male and female gelada exhaled grunts-a call type shared with baboons-have formant profiles that overlap more with human vowel space than do baboon grunts. These gelada grunts also contained more modulation of fundamental and formant frequencies than did baboon grunts. Second, we compared formant profiles and modulation of exhaled grunts to the derived call types (those not shared with baboons) produced by gelada males. These derived calls contained divergent formant profiles, and a subset of them, notably wobbles and vocalized yawns, were more modulated than grunts. Third, we investigated the rhythmic patterns of wobbles, a call type shown previously to contain cycles that match the 3-8 Hz tempo of speech. We use a larger dataset to show that the wobble rhythm overlaps more with speech rhythm than previously thought. We also found that variation in cycle duration depends on the production modality; specifically, exhaled wobbles were produced at a slower tempo than inhaled wobbles. Moreover, the variability in cycle duration within wobbles aligns with a linguistic property known as 'Menzerath's law' in that there was a negative association between cycle duration and wobble size (i.e. the number of cycles). Taken together, our results add to growing evidence that non-human primates are anatomically capable of producing modulated sounds. Our results also support and expand on current hypotheses of speech evolution, including the 'neural hypothesis' and the 'bimodal speech rhythm hypothesis'.