Articulatory and acoustic differences between lyric and dramatic singing in Western classical music.

Within the realm of voice classification, singers could be sub-categorized by the weight of their repertoire, the so-called "singer's Fach." However, the opposite pole terms "lyric" and "dramatic" singing are not yet well defined by their acoustic and articulatory characteristics. Nine professional singers of different singers' Fach were asked to sing a diatonic scale on the vowel /a/, first in what the singers considered as lyric and second in what they considered as dramatic. Image recording was performed using real time magnetic resonance imaging (MRI) with 25 frames/s, and the audio signal was recorded via an optical microphone system. Analysis was performed with regard to sound pressure level (SPL), vibrato amplitude, and frequency and resonance frequencies as well as articulatory settings of the vocal tract. The analysis revealed three primary differences between dramatic and lyric singing: Dramatic singing was associated with greater SPL and greater vibrato amplitude and frequency as well as lower resonance frequencies. The higher SPL is an indication of voice source changes, and the lower resonance frequencies are probably caused by the lower larynx position. However, all these strategies showed a considerable individual variability. The singers' Fach might contribute to perceptual differences even for the same singer with regard to the respective repertoire.

Dynamic changes of vocal tract dimensions with sound pressure level during messa di vocea).

The messa di voce (MdV), which consists of a continuous crescendo and subsequent decrescendo on one pitch is one of the more difficult exercises of the technical repertoire of Western classical singing. With rising lung pressure, regulatory adjustments both on the level of the glottis and the vocal tract are required to keep the pitch stable. The dynamic changes of vocal tract dimensions with the bidirectional variation of sound pressure level (SPL) during MdV were analyzed by two-dimensional real-time magnetic resonance imaging (25 frames/s) and synchronous audio recordings in 12 professional singer subjects. Close associations in the respective articulatory kinetics were found between SPL and lip opening, jaw opening, pharynx width, uvula elevation, and vertical larynx position. However, changes in vocal tract dimensions during plateaus of SPL suggest that perceived loudness could have been varied beyond the dimension of SPL. Further multimodal investigation, including the analysis of sound spectra, is needed for a better understanding of the role of vocal tract resonances in the control of vocal loudness in human phonation.

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 fR1:fo-tuning, wherein the first vocal tract resonance enhances the fundamental frequency, was applied until F6 (1396 Hz). An fR2:fo-tuning was not observed.

One-second MRI of a three-dimensional vocal tract to measure dynamic articulator modifications.

PURPOSE: To enable three-dimensional (3D) vocal tract imaging of dynamic singing or speech tasks at voxel sizes of 1.6 × 1.6 × 1.3 mm3 at 1.3 s per image. MATERIALS AND METHODS: A Stack-of-Stars method was implemented and enhanced to allow for fast and efficient k-space sampling of the box-shaped vocal tract using a 3 Tesla MRI system. Images were reconstructed using an off-line image reconstruction using compressed sensing theory, leading to the abovementioned spatial and temporal resolutions. To validate spatial resolution, a phantom with holes of defined sizes was measured. The applicability of the imaging method was validated in an eight-subject study of amateur singers that were required to sustain phonation at a constant pitch, past their comfortable expiratory level. A segmentation of the vocal tract over all phonation time steps was done for one subject. Anatomical distances (larynx position and pharynx width) were calculated and compared for all subjects. RESULTS: Analysis of the phantom study revealed that the imaging method could provide at least 1.6 mm isotropic resolution. Visual inspection of the segmented vocal tract during phonation showed modifications of the lips, tongue, and larynx position in all three dimensions. The mean larynx position per subject amounted to 52-85 mm, deviating up to 5% over phonation time. Parameter pharynx width was 32-181 mm2 on average per subject, deviating up to 16% over phonation time. Visual inspection of the parameter course revealed no common compensation strategy for long sustained phonation. CONCLUSION: The results of both phantom and in vivo measurements show the applicability of the fast 3D imaging method for voice research and indicate that modifications in all three dimensions can be observed and quantified. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:94-101.

Ensuring safety and functionality of electroglottography measurements during dynamic pulmonary MRI.

PURPOSE: To combine vocal tract measurements with dynamic MRI of the lungs to provide fundamental insights into the lung physiology during singing. METHODS: To analyze vocal fold oscillatory patterns during dynamic lung MRI, an electroglottography (EGG) system was modified to allow for simultaneous EGG measurements during MR image acquisitions. A low-pass filter was introduced to suppress residual radiofrequency (RF) coupling into the EGG signal. RF heating was tested in a gel phantom to ensure MR safety, and functionality of the EGG device was assessed in a volunteer experiment at singing frequencies from A5 to A3. In the recorded EGG signals, remaining RF interferences were removed by independent component analysis post processing, and standard EGG parameters such as fundamental frequency, contact quotient and jitter were calculated. In a second volunteer experiment, EGG recordings were compared with lung diameter measurements from 2D time-resolved trueFISP acquisitions. RESULTS: RF heating measurements resulted in less than 1.2°C temperature increase in the gel phantom. EGG parameters measured during MR imaging are within the range of ideal values. In the lung measurement, both the lung diameter and the EGG recordings could be successfully performed with only minimal interference. CONCLUSION: EGG recording is pos sible during dynamic lung MRI, and glottal activity can be studied safely at 1.5T. Magn Reson Med 76:1629-1635, 2016. © 2015 International Society for Magnetic Resonance in Medicine.

Acceleration of MRI of the vocal tract provides additional insight into articulator modifications.

PURPOSE: To accelerate dynamic imaging of the vocal tract during articulation. MATERIALS AND METHODS: Five subjects were imaged by magnetic resonance imaging (MRI) while repeating the word "Partikel" at 90 beats per minute, using both a radio-frequency-spoiled radial gradient echo sequence with golden angle projection rotation and a previously applied real-time Cartesian sequence. The acquired data were reconstructed using a CG-SENSE method and Cartesian reconstruction. The images from both methods were compared by measuring distances between anatomical landmarks that are important for resonance behavior of the vocal tract. Only commonly available hardware and software were used. RESULTS: With the presented radial method a spatial resolution of 1.8 mm at 25 frames per second could be achieved. Overall, the morphometric measurements of the vocal tract showed less deviation for the radial sequence both across repetitions and for all subjects. Fast modifications, such as complete lip closing, could be analyzed with greater fidelity using the high temporal resolution of the radial sequence. CONCLUSION: The results indicate that higher temporal resolution is a necessity to catch fast morphometric changes in the vocal tract.

A Comparison of Different Methods to Generate Tooth Surface Models Without Applying Ionizing Radiation for Digital 3-Dimensional Image Fusion With Magnetic Resonance Imaging-Based Data of the Head and Neck Region.

OBJECTIVE: The 3-dimensional display of the vocal tract and teeth is necessary in numerous clinical and scientific contexts. Due to the different tissue properties this can only be achieved by combining different imaging techniques. A comparison of methods to record the tooth surface to create combined models of the vocal tract and teeth without applying ionizing radiation is displayed in this study. METHODS: Four methods to record the tooth surface were compared concerning their clinical accuracy after combination with magnetic resonance imaging (MRI)-based vocal tract models. With 2 of the presented methods the information of the tooth surface was obtained from MRI data. With the other 2 methods, the tooth surface was captured using a digital and a conventional impression technique. RESULTS: Impression techniques received the best rating results. CONCLUSIONS: The digital 3-dimensional image fusion of dental impression and MRI resulted in a virtual model of the vocal tract and teeth with a high clinical accuracy without applying ionizing radiation.

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.

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.

Effects of Nasalization on Vocal Tract Response Curve.

BACKGROUND: Earlier studies have shown that nasalization affects the radiated spectrum by modifying the vocal tract transfer function in a complex manner. METHODS: Here we study this phenomenon by measuring sine-sweep response of 3-D models of the vowels /u, a, ᴂ, i/, derived from volumetric MR imaging, coupled by means of tubes of different lengths and diameters to a 3-D model of a nasal tract. RESULTS: The coupling introduced a dip into the vocal tract transfer function. The dip frequency was close to the main resonance of the nasal tract, a result in agreement with the Fujimura & Lindqvist in vivo sweep tone measurements [Fujimura & Lindqvist, 1972]. With increasing size of the coupling tube the depth of the dip increased and the first formant peak either changed in frequency or was split by the dip. Only marginal effects were observed of the paranasal sinuses. For certain coupling tube sizes, the spectrum balance was changed, boosting the formant peaks in the 2 - 4 kHz range. CONCLUSION: A velopharyngeal opening introduces a dip in the transfer function at the main resonance of the nasal tract. Its depth increases with the area of the opening and its frequency rises in some vowels.

Articulatory and Phonatory Precision When Singing Staccato at Different Speeds.

INTRODUCTION: Vocal tract adjustments are important for resonatory modification of the voice and also with respect to interactions concerning the voice source production. It is not clear, however, how fast, separated notes (staccato) influence vocal tract adjustments. MATERIAL AND METHODS: Twelve professional singers (four sopranos, three mezzo-sopranos, three tenors, and two baritones/basses) were recorded with dynamic real-time 2D-magnetic resonance imaging (MRI) with 25 fps singing a scale in legato and different staccato speeds (60, 120, 180, and 240 bps). From the MRI material, the lip opening, jaw opening, jaw protrusion, tongue position, pharynx width, and larynx position were measured. Furthermore, the fundamental frequency was analyzed from the simultaneously recorded audio signal after noise cancellation. RESULTS: The data show only very small differences between the legato and the staccato tasks and no great variations for different staccato speeds. During the pauses in between the staccato notes, minimal vocal tract adjustments were only detectable for the slowest staccato task. CONCLUSION: There are no great differences in the vocal tract shapes for legato singing in contrast to staccato phonation and no great differences for different staccato speeds.

The influence of gravity on respiratory kinematics during phonation measured by dynamic magnetic resonance imaging.

Respiratory kinematics are important for the regulation of voice production. Dynamic MRI is an excellent tool to study respiratory motion providing high-resolution cross-sectional images. Unfortunately, in clinical MRI systems images can only be acquired in a horizontal subject position, which does not take into account gravitational effects on the respiratory apparatus. To study the effect of body posture on respiratory kinematics during phonation, 8 singers were examined both in an open-configuration MRI with a rotatable gantry and a conventional horizontal MRI system. During dynamic MRI the subjects sang sustained tones at different pitches in both supine and upright body positions. Sagittal images of the respiratory system were obtained at 1-3 images per second, from which 6 anatomically defined distances were extracted to characterize its movements in the anterior, medium and posterior section of the diaphragm as well as the rip cage (diameter at the height of the 3rd and 5th rip) and the anterior-posterior position of the diaphragm cupola. Regardless of body position, singers maintained their general principles of respiratory kinematics with combined diaphragm and thorax muscle activation for breath support. This was achieved by expanding their chest an additional 20% during inspiration when singing in the supine position but not for sole breathing. The diaphragm was cranially displaced in supine position for both singing and breathing and its motion range increased. These results facilitate a more realistic extrapolation of research data obtained in a supine position.

Respiratory kinematics and the regulation of subglottic pressure for phonation of pitch jumps - a dynamic MRI study.

The respiratory system is a central part of voice production as it contributes to the generation of subglottic pressure, which has an impact on voice parameters including fundamental frequency and sound pressure level. Both parameters need to be adjusted precisely during complex phonation tasks such as singing. In particular, the underlying functions of the diaphragm and rib cage in relation to the phonation of pitch jumps are not yet understood in detail. This study aims to analyse respiratory movements during phonation of pitch jumps using dynamic MRI of the lungs. Dynamic images of the breathing apparatus of 7 professional singers were acquired in the supine position during phonation of upwards and downwards pitch jumps in a high, medium, and low range of the singer's tessitura. Distances between characteristic anatomical landmarks in the lung were measured from the series of images obtained. During sustained phonation, the diaphragm elevates, and the rib cage is lowered in a monotonic manner. During downward pitch jumps the diaphragm suddenly changed its movement direction and presented with a short inspiratory activation which was predominant in the posterior part and was associated with a shift of the cupola in an anterior direction. The magnitude of this inspiratory movement was greater for jumps that started at higher compared to lower fundamental frequency. In contrast, expiratory movement of the rib cage and anterior diaphragm were simultaneous and continued constantly during the jump. The data underline the theory of a regulation of subglottic pressure via a sudden diaphragm contraction during phonation of pitch jumps downwards, while the rib cage is not involved in short term adaptations. This strengthens the idea of a differentiated control of rib cage and diaphragm as different functional units during singing phonation.

The Influence of Vowels on Vocal Fold Dynamics in the Tenor's Passaggio.

INTRODUCTION: The influence of vowels on the frequency region where registration events in male voices usually occur (passaggio) has not yet been clarified. Particularly, for tenors who frequently have to sing across the passaggio, it might be assumed that the vowel quality has an influence on the stability of phonation. METHODS: In this investigation, six professionally trained Western classical tenors performed a glide from A3 (220 Hz) to A4 (440 Hz) and were recorded using high-speed videoendoscopy at 20,000 fps via transnasal flexible endoscopy. The participants produced transitions (1) from modal register to falsetto and (2) from modal register to stage voice above the passaggio on the vowels [aː], [iː], and [uː]. Simultaneously, acoustic and electroglottographic (EGG) signals were recorded. The glottal area waveform (GAW) open quotient (OQ), the EGG OQ, and the sample entropy derived from the EGG were calculated and phonovibrograms were established. RESULTS: In comparison to [iː] and [uː], vowel [aː] showed lower values regarding the sample entropy and greater periodicity in the phonovibrograms during the passaggio. For [iː] and [uː], the falsetto showed greater GAW OQ than the stage voice above the passaggio but no great difference for vowel [aː]. There was a good agreement between GAW OQ and EGG OQ for GAW OQ values below .65. However, for values greater than .65, the EGG OQ showed greater disagreement. CONCLUSIONS: The data support the hypothesis that the vowel condition influences the phonatory stability concerning the passaggio, suggesting that vowel [aː] is associated with greater phonation stability.

Oscillatory Characteristics of the Vocal Folds Across the Tenor Passaggio.

INTRODUCTION: Recent research has revealed that classically trained tenors tend to constrict epilaryngeal structures when singing in and above the passaggio (ie, the frequency region where register events typically occur). These constrictions complicate visibility of vocal fold oscillatory patterns with transoral rigid high-speed video endoscopy, thus limiting the current understanding of laryngeal dynamics in the passaggio region of tenors. MATERIALS AND METHODS: This investigation analyzed seven professionally trained western classical tenors using high-speed digital imaging (HSDI) at 20,000 frames per second via transnasal flexible endoscopy. The participants produced transitions (a) from modal to falsetto register and (b) from modal to stage voice above the passaggio (SVaP) during ascending pitch glides from A3 (220 Hz) to A4 (440 Hz) on vowel /i/. HSDI data were complemented by simultaneous acoustic and electroglottographic recordings. RESULTS: For many subjects both transition types were associated with constrictions of the epilaryngeal structures during the pitch glide. These constrictions appeared to be more distinct for the SVaP than for falsetto. No major irregularities of vocal fold oscillations in the sense of fundamental frequency jumps were observed for either transition type. However, during the transitions, the open quotient derived from the glottal area waveform (OQGAW) increased; in falsetto, the OQGAW was greater and the electroglottographic cepstral peak prominence was lower than in SVaP. CONCLUSIONS: Epilaryngeal constrictions should be considered typical for tenors singing at high fundamental frequencies. Vocal fold oscillatory patterns are changing not only for the register shift from modal to falsetto but also for the transition from modal to SVaP, indicating a need for laryngeal adjustments during these transitions.

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 (ƒo = 220 Hz) to A4 (ƒo = 440 Hz) and from A4 (ƒo = 440 Hz) to A5 (ƒo = 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.

The influence of vocal fold mass lesions on the passaggio region of professional singers.

OBJECTIVES/HYPOTHESIS: In professional classical singing, an even voice quality throughout the entire singing voice range is essential. Transitions between vocal registers (passaggio) are the technically most challenging aspects in classical singing. It is hypothesized that they are most affected by vocal fold mass lesions (VFML). STUDY DESIGN: Cohort study. METHODS: In this study, the effect of VFML on vocal fold vibration in the passaggio regions was analyzed in four female and three male singers suffering from organic dysphonia. The singers were asked to sing an ascending glissando through the passaggio regions, before and after treatment. The vocal fold vibration was documented with transnasal endoscopic high-speed imaging recordings at 20,000 frames per second, supplemented by synchronized acoustic and electroglottographic recordings. RESULTS: Major irregularities were found in the passaggio region of four singers before treatment, whereas the respective phonations below the passaggio were almost regular. In two female singers only the upper, but not the lower passaggio was affected. In all four of these participants, the passaggio region was more regular after treatment. In the remaining three participants, the VFML showed no effect on the passaggio region. However, the singers' ability to reach higher pitches was impaired, but was resolved after treatment. CONCLUSIONS: The data in this case study strongly suggest that the passaggio region could be affected by VFML, even if phonation outside the passaggio regions is unimpaired. When planning surgical procedures for professional singers, clinical examination protocols should therefore include phonatory tests across the passaggio regions. LEVEL OF EVIDENCE: 4 Laryngoscope, 127:1392-1401, 2017.

Respiratory dynamics in phonation and breathing-A real-time MRI study.

The respiratory system is a central part of voice production, but for phonation neither the underlying functional relations between diaphragm (DPH) and rib cage (RC), nor differences to normal breathing are yet understood. This study aims to compare respiratory dynamics in phonation and breathing via dynamic MRI of the lung. Images of the breathing apparatus of 6 professional singers were captured in a 1.5T MRI system in supine position during vital capacity breathing and maximal long sustained phonation at 3 different pitches and loudness conditions. In a dynamic series of cross-sectional images of the lung, distances between characteristic anatomical landmarks were measured. During exhalation in normal breathing the diaphragm and rib cage moved synchronously to reduce lung volume, but during phonation different functional units could be identified, which support phonation by facilitating the control of subglottic pressure.

Relevance of the Implementation of Teeth in Three-Dimensional Vocal Tract Models.

Purpose: Recently, efforts have been made to investigate the vocal tract using magnetic resonance imaging (MRI). Due to technical limitations, teeth were omitted in many previous studies on vocal tract acoustics. However, the knowledge of how teeth influence vocal tract acoustics might be important in order to estimate the necessity of implementing teeth in vocal tract models. The aim of this study was therefore to estimate the effect of teeth on vocal tract acoustics. Method: The acoustic properties of 18 solid (3-dimensional printed) vocal tract models without teeth were compared to the same 18 models including teeth in terms of resonance frequencies (fRn). The fRn were obtained from the transfer functions of these models excited by white noise at the glottis level. The models were derived from MRI data of 2 trained singers performing 3 different vowel conditions (/i/, /a/, and /u/) in speech and low-pitched and high-pitched singing. Results: Depending on the oral configuration, models exhibiting side cavities or side branches were characterized by major changes in the transfer function when teeth were implemented via the introduction of pole-zero pairs. Conclusions: To avoid errors in modeling, teeth should be included in 3-dimensional vocal tract models for acoustic evaluation. Supplemental Material: https://doi.org/10.23641/asha.5386771.