Physical definition of the "flageolet register"

The Physiology of Vocal Damping: Historical Overview and Descriptive Insights in Professional Singers

OBJECTIVE

Vocal damping has been historically described as a distinctive phonatory glottic behavior where the posterior part of the vocal folds is strongly adducted and vibration occurs in the anterior part. The aim of the present descriptive study is to analyze anterior glottis phonation patterns in professional singers through a multidimensional approach, in order to better understand the physiological underpinnings of vocal damping and their relation to glottic vibratory mechanisms.

METHODS

Ten professional singers (five males and five females) with no vocal complaints were recruited. Each subject was asked to produce ascending and descending glissandos in a spontaneous way; sustained vowels and little sung fragments in vocal fry, chest voice, falsetto, and whistle register. Each singer was asked to produce - where possible - damping sounds. A multidimensional investigation including acoustic analysis, electroglottography, and videolaryngostroboscopy was carried out.

RESULTS

Among the enrolled singers, nine out of 10 successfully produced vocalizations with a typical anterior-vibrating glottic pattern indicative of damping. All nine singers achieved a damping glottic configuration when vocalizing in the falsetto register and five were consciously able to switch between a full-glottic falsetto and a damping falsetto upon request. Three male and two female singers were able to produce a damping glottic configuration while emitting whistle notes. Three male singers demonstrated damping glottic configurations when producing high pitched chest notes.

CONCLUSIONS

In conclusion, it is possible to state that damping is an existing and documentable glottic behavior, with a wide range of manifestations across vocal registers. The present preliminary study describes damping in the domains of chest voice, falsetto, and whistle register. A proper damping phenomenon, defined as the modification of the glottic vibratory boundaries according to pitch variations, is described for M2 emissions, both in male and female larynx. The analysis of passaggio patterns allows to describe damping-M2 as a possible vibratory submechanism.

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.

Biomechanics of sound production in high-pitched classical singing

Voice production of humans and most mammals is governed by the MyoElastic-AeroDynamic (MEAD) principle, where an air stream is modulated by self-sustained vocal fold oscillation to generate audible air pressure fluctuations. An alternative mechanism is found in ultrasonic vocalizations of rodents, which are established by an aeroacoustic (AA) phenomenon without vibration of laryngeal tissue. Previously, some authors argued that high-pitched human vocalization is also produced by the AA principle. Here, we investigate the so-called "whistle register" voice production in nine professional female operatic sopranos singing a scale from C6 (≈ 1047 Hz) to G6 (≈ 1568 Hz). Super-high-speed videolaryngoscopy revealed vocal fold collision in all participants, with closed quotients from 30 to 73%. Computational modeling showed that the biomechanical requirements to produce such high-pitched voice would be an increased contraction of the cricothyroid muscle, vocal fold strain of about 50%, and high subglottal pressure. Our data suggest that high-pitched operatic soprano singing uses the MEAD mechanism. Consequently, the commonly used term "whistle register" does not reflect the physical principle of a whistle with regard to voice generation in high pitched classical singing.

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.

Dynamic Analysis Of Male "Extra-high Voice" Using Multi-row Detector Computed Tomography

OBJECTIVES/HYPOTHESIS

Some people who practice singing on a daily basis may be able to produce a voice higher than the upper limit of the normal range (extra high voice), but there is much regarding the movement of the larynx that remains unknown. We have been conducting dynamic analysis of the larynx using multi-row detection computed tomography (MD-CT) at our university and report herein an analysis of the extra high voice.

STUDY DESIGN

Observational.

METHODS

Images of a normal male participant capable of extremely high-frequency speech (the highest speech range is C7 [2093 Hz] and the singing application range is up to B5 [988 Hz]) during speech were captured by MD-CT. The acquisition time was 2 seconds, and the rise of the voice from low to high and then to very high tones was recorded. Ten frames per second were analyzed as three-dimensional images.

RESULTS

In the fundamental frequency range from A3 to D5 (220-587 Hz), laryngeal elevation movements were observed as the voice rose in pitch. However, posterior upward displacement of the laryngeal cartilage was observed as the frequency range increased from E5 to B5 (659-988 Hz).

CONCLUSIONS

In the E5-B5 range, laryngeal movements were different from those observed in the previous range. MD-CT analysis is useful in the study of this range because it allows visualization of laryngeal movements that are unclear using endoscopy or external examination.

Investigation of resonance strategies of high pitch singing sopranos using dynamic three-dimensional magnetic resonance imaging

Resonance-strategies with respect to vocal registers, i.e., frequency-ranges of uniform, demarcated voice quality, for the highest part of the female voice are still not completely understood. The first and second vocal tract resonances usually determine vowels. If the fundamental frequency exceeds the vowel-shaping resonance frequencies of speech, vocal tract resonances are tuned to voice source partials. It has not yet been clarified if such tuning is applicable for the entire voice-range, particularly for the top pitches. We investigated professional sopranos who regularly sing pitches above C6 (1047 Hz). Dynamic three-dimensional (3D) magnetic resonance imaging was used to calculate resonances for pitches from C5 (523 Hz) to C7 (2093 Hz) with different vowel configurations ([a:], [i:], [u:]), and different contexts (scales or octave jumps). A spectral analysis and an acoustic analysis of 3D-printed vocal tract models were conducted. The results suggest that there is no exclusive register-defining resonance-strategy. The intersection of fundamental frequency and first vocal tract resonance was not found to necessarily indicate a register shift. The articulators and the vocal tract resonances were either kept without significant adjustments, or the f_R1:f_o-tuning, wherein the first vocal tract resonance enhances the fundamental frequency, was applied until F6 (1396 Hz). An f_R2:f_o-tuning was not observed.

Using visual feedback to tune the second vocal tract resonance for singing in the high soprano range

PURPOSE

Over a range roughly C5-C6, sopranos usually tune their first vocal tract resonance (R1) to the fundamental frequency (f_o) of the note sung: R1:f_o tuning. Those who sing well above C6 usually adjust their second vocal tract resonance (R2) and use R2:f_o tuning. This study investigated these questions: Can singers quickly learn R2:f_o tuning when given suitable feedback? Can they subsequently use this tuning without feedback? And finally, if so, does this assist their singing in the high range?

METHODS

New computer software for the technique of resonance estimation by broadband excitation at the lips was used to provide real-time visual feedback on f_o and vocal tract resonances. Eight sopranos participated. In a one-hour session, they practised adjusting R2 whilst miming (i.e. without phonating), and then during singing.

RESULTS

Six sopranos learned to tune R2 over a range of several semi-tones, when feedback was present. This achievement did not immediately extend their singing range. When the feedback was removed, two sopranos spontaneously used R2:f_o tuning at the top of their range above C6.

CONCLUSIONS

With only one hour of training, singers can learn to adjust their vocal tract shape for R2:f_o tuning when provided with visual feedback. One additional participant who spent considerable time with the software, acquired greater skill at R2:f_o tuning and was able to extend her singing range. A simple version of the hardware used can be assembled using basic equipment and the software is available online.

Laryngeal evidence for the first and second passaggio in professionally trained sopranos

Introduction

Due to a lack of empirical data, the current understanding of the laryngeal mechanics in the passaggio regions (i.e., the fundamental frequency ranges where vocal registration events usually occur) of the female singing voice is still limited.

Material and methods

In this study the first and second passaggio regions of 10 professionally trained female classical soprano singers were analyzed. The sopranos performed pitch glides from A3 (ƒ_o = 220 Hz) to A4 (ƒ_o = 440 Hz) and from A4 (ƒ_o = 440 Hz) to A5 (ƒ_o = 880 Hz) on the vowel [iː]. Vocal fold vibration was assessed with trans-nasal high speed videoendoscopy at 20,000 fps, complemented by simultaneous electroglottographic (EGG) and acoustic recordings. Register breaks were perceptually rated by 12 voice experts. Voice stability was documented with the EGG-based sample entropy. Glottal opening and closing patterns during the passaggi were analyzed, supplemented with open quotient data extracted from the glottal area waveform.

Results

In both the first and the second passaggio, variations of vocal fold vibration patterns were found. Four distinct patterns emerged: smooth transitions with either increasing or decreasing durations of glottal closure, abrupt register transitions, and intermediate loss of vocal fold contact. Audible register transitions (in both the first and second passaggi) generally coincided with higher sample entropy values and higher open quotient variance through the respective passaggi.

Conclusions

Noteworthy vocal fold oscillatory registration events occur in both the first and the second passaggio even in professional sopranos. The respective transitions are hypothesized to be caused by either (a) a change of laryngeal biomechanical properties; or by (b) vocal tract resonance effects, constituting level 2 source-filter interactions.

Articulation and vocal tract acoustics at soprano subject's high fundamental frequencies

The role of the vocal tract for phonation at very high soprano fundamental frequencies (F0s) is not yet understood in detail. In this investigation, two experiments were carried out with a single professional high soprano subject. First, using two dimensional (2D) dynamic real-time magnetic resonance imaging (MRI) (24 fps) midsagittal and coronal vocal tract shapes were analyzed while the subject sang a scale from Bb5 (932 Hz) to G6 (1568 Hz). In a second experiment, volumetric vocal tract MRI data were recorded from sustained phonations (13 s) for the pitches C6 (1047 Hz) and G6 (1568 Hz). Formant frequencies were measured in physical models created by 3D printing, and calculated from area functions obtained from the 3D vocal tract shapes. The data showed that there were only minor modifications of the vocal tract shape. These changes involved a decrease of the piriform sinus as well as small changes of tongue position. Formant frequencies did not exhibit major differences between C6 and G6 for F1 and F3, respectively. Only F2 was slightly raised for G6. For G6, however, F2 is not excited by any voice source partial. Therefore, this investigation was not able to confirm that the analyzed professional soprano subject adjusted formants to voice source partials for the analyzed F0s.

Vocal fold vibrations at high soprano fundamental frequencies

Human voice production at very high fundamental frequencies is not yet understood in detail. It was hypothesized that these frequencies are produced by turbulences, vocal tract/vocal fold interactions, or vocal fold oscillations without closure. Hitherto it has been impossible to visually analyze the vocal mechanism due to technical limitations. Latest high-speed technology, which captures 20,000 frames/s, using transnasal endoscopy was applied. Up to 1568 Hz human vocal folds do exhibit oscillations with complete closure. Therefore, the recent results suggest that human voice production at very high F0s up to 1568 Hz is not caused by turbulence, but rather by airflow modulation from vocal fold oscillations.

Glottal behavior in the high soprano range and the transition to the whistle register

The high soprano range was investigated by acoustic and electroglottographic measurements of 12 sopranos and high-speed endoscopy of one of these. A single laryngeal transition was observed on glissandi above the primo passaggio. It supports the existence of two distinct laryngeal mechanisms in the high soprano range: M2 and M3, underlying head and whistle registers. The laryngeal transition occurred gradually over several tones within the interval D#5-D6. It occurred over a wider range and was completed at a higher pitch for trained than untrained sopranos. The upper limit of the laryngeal transition during glissandi was accompanied by pitch jumps or instabilities, but, for most singers, it did not coincide with the upper limit of R1:f(0) tuning (i.e., tuning the first resonance to the fundamental frequency). However, pitch jumps could also be associated with changes in resonance tuning. Four singers demonstrated an overlap range over which they could sing with a full head or fluty resonant quality. Glottal behaviors underlying these two qualities were similar to the M2 and M3 mechanisms respectively. Pitch jumps and discontinuous glottal and spectral changes characteristic of a M2-M3 laryngeal transition were observed on decrescendi produced within this overlap range.

Vocal tract adjustments in the high soprano range

Twelve sopranos with different levels of expertise (4 nonexperts, 4 advanced, 4 professionals) sustained pitches from A4 ( approximately 440 Hz) to their highest pitch (ranging from C6 to D7, i.e., from approximately 1000 to 2300 Hz). The frequencies of their first two vocal tract resonances (R1 and R2) were measured by broadband excitation at the mouth and compared with the voice harmonics (f(0), 2f(0), etc). Lip articulation was measured from simultaneous video recordings. Adjustment of R1 near to f(0) (R1:f(0) tuning) was observed below C6 to D6 ( approximately 1000-1200 Hz) for both expert and non-expert singers. Experts began this tuning at lower pitches. Some singers combine R2:2f(0) adjustment with R1:f(0) tuning. Some singers increased mouth area with increasing pitch over the whole R1:f(0) tuning range. Other singers showed this strategy on the higher part of the R1:f(0) range only, and used another, as yet unidentified, articulatory strategy on the lower part. To achieve very high pitches, some singers extended the range of R1:f(0) tuning as far as E6 to F#6 ( approximately 1300-1500 Hz) while others adjusted R2 near f(0) over the highest pitch range.

Mirroring the voice from Garcia to the present day: Some insights into singing voice registers

Starting from Garcia's definition, the historical evolution of the notion of vocal registers from then until now is considered. Even though much research has been carried out on vocal registers since then, the notion of registers is still confused in the singing voice community, and defined in many different ways. While some authors consider a vocal register as a totally laryngeal event, others define it in terms of overall voice quality similarities. This confusion is reflected in the multiplicity of labellings, and it lies in the difficulty of identifying and specifying the mechanisms distinguished by these terms. The concept of laryngeal mechanism is then introduced, on the basis of laryngeal transition phenomena detected by means of electroglottography. It helps to specify at least the laryngeal nature of a given singing voice register. On this basis, the main physiological, acoustic, and perceptual characteristics of the most common singing voice registers are surveyed.

Laryngeal Mechanisms During Human 4-kHz Vocalization Studied With CT, Videostroboscopy, and Color Doppler Imaging

The objective of this study was to investigate the underlying laryngeal mechanisms during the specific human 4-kHz vocalization. The laryngeal configuration during this vocalization was measured using high-resolution computerized tomographic scan and videostrobolaryngoscopy. The color Doppler imaging (CDI) of medical ultrasound was used to detect the vibrations of glottal and supraglottal mucosa. During the 4-kHz vocalization, the ventricular folds were adducted in the shape of a bimodal chink and the vocal folds were shaped as a "V" with an opening at the posterior glottis. In the coronal view, the laryngeal ventricles had collapsed and a divergent shaped conduit was observed at the posterior portion of the larynx. The surface mucosa vibration detected by CDI was noted over the bilateral ventricular folds and aryepiglottic folds. The vibration displacement was estimated to be on the order of 0.1mm. This vibration amplitude was too small to be detected in videostrobolaryngoscopy. The laryngeal configuration and CDI data suggested a diffuser jet with periodic vorticity bursts in the larynx producing 4 kHz voice.

Three registers in an untrained female singer analyzed by videokymography, strobolaryngoscopy and sound spectrography

There has been a lack of objective data on the singing voice registers, particularly on the so called "whistle" register, occurring in the top part of the female pitch range, which is accessible only to some singers. This study offers unique strobolaryngoscopic and high-speed (7812.5 imagess) videokymographic data on the vocal fold behavior of an untrained female singer capable of producing three distinct voice qualities, i.e., the chest, head and whistle registers. The sound was documented spectrographically. The transition from chest to head register, accompanied by pitch jumps, occurred around tones B4-C#5 (500-550 Hz) and was found to be associated with a slight decrease in arytenoids adduction, resulting in decrease of the closed quotient. The register shifts from head to whistle, also accompanied by pitch jumps, occurred around tones E5-B5 (670-1000 Hz) without any noticeable changes in arytenoids adduction. Some evidence was found for the vocal tract influence on this transition. The mechanism of the vocal fold vibration in whistle register was found principally similar to that at lower registers: vibrations along the whole glottal length and vertical phase differences (indicated by sharp lateral peaks in videokymography) were seen on the vocal folds up to the highest tone G6 (1590 Hz).

Comparison of vocal tract formants in singing and nonperiodic phonation

The skilled use of nonperiodic phonation techniques in combination with spectrum analysis has been proposed here as a practical method for locating formant frequencies in the singing voice. The study addresses the question of the degree of similarity between sung phonations and their nonperiodic imitations, with respect to both frequency of the first two formants as well as posture of the vocal tract. Using magnetic resonance imaging (MRI), linear predictive coding (LPC), and spectrum analysis, two types of nonperiodic phonation (ingressive and vocal fry) are compared with singing phonations to determine the degree of similarity/difference in acoustic and spatial dimensions of the vocal tract when these phonation types are used to approximate the postures of singing. In comparing phonation types, the close similarity in acoustic data in combination with the relative dissimilarity in spatial data indicates that the accurate imitations are not primarily the result of imitating the singing postures, but have instead an aural basis.

Bifurcations in excised larynx experiments

Bifurcation analysis was applied to vocal fold vibration in excised larynx experiments. Phonation onset and vocal instabilities were studied in a parameter plane spanned by subglottal pressure and asymmetry of either vocal fold adduction or elongation. Various phonatory regimes were observed, including single vocal fold oscillations. Selected spectra demonstrated correspondence between these regimes and vocal registers noted in the literature. To illustrate the regions spanned by the various phonatory regimes, two-dimensional bifurcation diagrams were generated. Many instabilities or bifurcations were noted in the regions of coexistence, i.e., regions in which the phonatory regimes overlap. Bifurcations were illustrated with spectrograms and fundamental frequency contours. Where possible, results from these studies were related to clinical observations.

Fundamental frequency and tracheal pressure during three types of vocalizations elicited from anesthetized dogs

Electrical stimulation of the midbrain was used to elicit a variety of vocalizations from six anesthetized dogs. This study was conducted to investigate the ranges of and relationships between fundamental frequency of the vocalizations (F0) and tracheal pressure (Pt) produced during the vocalizations. The vocalizations were described according to type (growl, howl, and whine); F0 and Pt, as well as patterns of laryngeal muscle activity, were examined for each vocalization type. Natural-sounding growl and howl vocalizations were elicited from five dogs; three dogs also produced whines. With few exceptions, F0 was categorically different for the three vocalization types (low for growls, average for howls, very high for whines). Pt values overlapped for the three vocalization types, although, on average, howls were produced with greater Pt than growls. Patterns and degrees of laryngeal muscle activity varied across and within vocalization types, but general findings were consistent with the presumed function of most of the muscles. Laryngeal muscle activity may help explain some of the variability in the acoustic and aerodynamic data.