Vocal Tract in Female Registers—A Dynamic Real-Time MRI Study

Three Professional Singers' Vocal Tract Dimensions in Operatic Singing, Kulning, and Edge-A Multiple Case Study Examining Loud Singing

OBJECTIVE

A comprehensive understanding of how vocal tract dimensions vary among different types of loud voice productions has not yet been fully formed. This study aims to expand the existing knowledge on the topic.

METHODS

Three trained professional singers together practiced the vocal techniques underlying Opera and Kulning singing styles for one hour and, afterwards, phonated using these techniques on vowel [iː] at pitch C5 (523 Hz), while their vocal tracts were scanned via MRI. One of the participants also produced the samples in the Edge vocal mode using [ɛː]. Several dimensional vocal tract measurements were calculated from the MRIs. Spectral analysis was conducted on the filtered audio recorded during the MRI.

RESULTS

The Operatic technique demonstrated a lower larynx, a larger tongue-palate distance, and larger epilaryngeal and pharyngeal tube diameters compared to Kulning. Edge showed the highest laryngeal position, narrowest pharynx and epilarynx tubes, and the least forward-tilted larynx out of the styles studied. The spectra of Opera and Kulning showed a dominant first harmonic, while in Edge, the second harmonic was the strongest.

CONCLUSIONS

The results shed light on the magnitude of vocal tract changes necessary for genre-typical vocal projection. This information can be pedagogically helpful.

Oropharyngeal and Aryepiglottic Narrowing for Twang: A Magnetic Resonance Imaging Study

OBJECTIVE

This study aimed to compare vocal tract configurations between speech and twang qualities.

METHODS

Magnetic resonance imaging data were acquired from five professional vocalists while producing the sustained vowel /i/. Width and area measurements were obtained from the axial (ie, transverse) images to evaluate oropharyngeal narrowing and aryepiglottic (AES) narrowing.

RESULTS

Four out of five participants exhibited a smaller vocal tract area for twang than for speech at the oropharyngeal level, with the extent of narrowing ranging from 18.8% to 49.6%. Only one participant showed a meaningful decrease in oropharyngeal anteroposterior (AP) width, while three participants showed meaningful decreases in oropharyngeal mediolateral (ML) width for twang compared to speech. At the AES level, all participants showed a smaller vocal tract area for twang than for speech, with the extent of narrowing ranging from 11.8% to 52.4%. Two participants exhibited meaningful decreases in AES AP width, while three participants showed meaningful decreases in AES ML width for twang compared to speech.

CONCLUSIONS

Axial imaging revealed oropharyngeal and AES narrowing associated with twang, more prominent in the ML than the AP dimension. Notable individual variations in the mechanism and degree of narrowing at the oropharyngeal and AES levels were observed. The degree of narrowing varied among participants, highlighting the complexity of physiological maneuvers involved in twang production. Future research is necessary to identify broader patterns in twang production for effective pedagogic and therapeutic applications.

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.

Towards Automated Vocal Mode Classification in Healthy Singing Voice-An XGBoost Decision Tree-Based Machine Learning Classifier

Auditory-perceptual assessment is widely used in clinical and pedagogical practice for speech and singing voice, yet several studies have shown poor intra- and inter-rater reliability in both clinical and singing voice contexts. Recent advances in artificial intelligence and machine learning offer models for automated classification and have demonstrated discriminatory power in both pathological and healthy voice. This study develops and tests an XGBoost decision tree based machine learning classifier to develop automated vocal mode classification in healthy singing voice. Classification models trained on mel-frequency cepstrum coefficients, MFCC-Zero-Time Windowing, glottal features, voice quality features, and α-ratios demonstrated 92% average F1-score accuracy in distinguishing metallic and non-metallic singing for male singers and 87% average F1-score for female singers. The model distinguished vocal modes with 70% and 69% average F1-score for male and female samples, respectively. Model performance was compared to human auditory-perceptual assessments of 64 corresponding samples performed by 41 professional singers. The model performed with approximating or subpar performance to human assessors on task-matched problems. The XGBoost gains observed across tested features reveal that the most important attributes for the tested classification problems were MFCCs and α-ratios between high and low frequency energy, with models trained on only these features achieving performance not statistically significantly different from the best tested models. The best automated models in this study do not yet match human auditory-perceptual discrimination but improve on previously reported F1-average accuracies in automated classification in singing voice.

Simulation of Vocal Loudness Regulation with Lung Pressure, Vocal Fold Adduction, and Source-Airway Interaction

In speaking, shouting, and singing, vocal loudness is known to be regulated with lung pressure, but the degree to which vocal fold adduction and airway shape play a role in loudness control is less well known. When loudness is quantified in sones instead of sound pressure level (SPL), the regulatory mechanisms are even less obvious. Here it is shown computationally that loudness is insensitive to changes in SPL produced with variable adduction. A trade-off exists between a reduction in glottal flow amplitude and a flatter spectral slope. When the airway configuration is changed from a uniform tube to a "belt" or "call" shape, loudness can increase with a slight decrease in SPL. When the airway configuration is changed from a uniform tube to an operatic "ring" shape, loudness is increased with only a small increase in SPL.

Finite element modeling of the effects of velopharyngeal opening on vocal tract reactance in female voice

Classical singers use nasal consonants as "resonance exercises," and experimental results have shown that singers may use some velopharyngeal opening (VPO), most often in [a:] and more seldom in [i:] or [u:]. In particular, male singers have been found to increase VPO as pitch rises toward register change frequencies (passaggi). Laryngoscopic findings have shown that some VPO stabilizes vocal fold vibration; the effect is related to positive reactance. This study investigates the effects of VPO on vocal tract (VT) reactance over the range of fundamental frequencies (f₀) used in singing using a computerized tomography-based finite element model of the VT and nose of a female. According to the results, by raising the lowest VT resonances, the VPO increased the VT reactance in the frequency ranges 207-359 Hz for [i:], 265-411 Hz for [u:], and 500-611 Hz for [a:], depending on the VPO size (full or half VPO). These frequency ranges are close to the first and second passaggio of a female singer. The change may have an especially practical stabilizing effect for [a:], which is otherwise characterized by very large changes in VT reactance and negative reactance at the second passaggio.

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.

Realistic Dynamic Numerical Phantom for MRI of the Upper Vocal Tract

Dynamic and real-time MRI (rtMRI) of human speech is an active field of research, with interest from both the linguistics and clinical communities. At present, different research groups are investigating a range of rtMRI acquisition and reconstruction approaches to visualise the speech organs. Similar to other moving organs, it is difficult to create a physical phantom of the speech organs to optimise these approaches; therefore, the optimisation requires extensive scanner access and imaging of volunteers. As previously demonstrated in cardiac imaging, realistic numerical phantoms can be useful tools for optimising rtMRI approaches and reduce reliance on scanner access and imaging volunteers. However, currently, no such speech rtMRI phantom exists. In this work, a numerical phantom for optimising speech rtMRI approaches was developed and tested on different reconstruction schemes. The novel phantom comprised a dynamic image series and corresponding k-space data of a single mid-sagittal slice with a temporal resolution of 30 frames per second (fps). The phantom was developed based on images of a volunteer acquired at a frame rate of 10 fps. The creation of the numerical phantom involved the following steps: image acquisition, image enhancement, segmentation, mask optimisation, through-time and spatial interpolation and finally the derived k-space phantom. The phantom was used to: (1) test different k-space sampling schemes (Cartesian, radial and spiral); (2) create lower frame rate acquisitions by simulating segmented k-space acquisitions; (3) simulate parallel imaging reconstructions (SENSE and GRAPPA). This demonstrated how such a numerical phantom could be used to optimise images and test multiple sampling strategies without extensive scanner access.

Dynamic Fast Imaging Employing Steady State Acquisition Magnetic Resonance Imaging of the Vocal Tract in One Overtone Male Singer: Our Preliminary Experience

AIMS

To demonstrate physiological changing of vocal tract's structures during overtone singing with commercial magnetic resonance imaging (MRI) Fast Imaging Employing Steady State Acquisition (FIESTA) dynamic sequence.

METHODS AND MATERIALS

A 1.5 T MRI with a 16 channel head-and-neck coil and a FIESTA sequence were used. A temporal resolution of 0.155 sec (7 image/s). A single professional singer was studied. The MR acquisition is made while the singer performed a predetermined singing sequence. Three different overtone singing techniques were examined (L-technique, J-technique, and NG technique) and one effect (Ezengileer) applied to L-technique. For each overtone technique we evaluated MRI movement of lips, tongue, velopharyngeal closure, and relationship among tongue and pharyngeal posterior wall/soft palate. To cancel the noise over-imposed, the dynamic MRI was subsequently dubbed in studio with the audio of the preset overtone sing. Dubbed MR images were analyzed with an Overtone Analyzer Software and different sound frequencies were identified and pointed out as colored lines.

RESULTS

This study shows that different overtone techniques are related to a specific conformation of tongue, lips, soft and hard palate and motion's relation changing between them. Only a correct conformation of vocal tract's structure allows resonance and so to hear desired fundamental and harmonic pitch in overtone singing.

CONCLUSION

The preliminary data of our study demonstrates that FIESTA dynamic MRI sequence can be used to depict changing of position of vocal tract's structure in overtone singing techniques with a good temporal and anatomic resolution.

Assessment of Tongue Position and Laryngeal Height in Two Professional Voice Populations

Purpose To advance our current knowledge of singer physiology by using ultrasonography in combination with acoustic measures to compare physiological differences between musical theater (MT) and opera (OP) singers under controlled phonation conditions. Primary objectives addressed in this study were (a) to determine if differences in hyolaryngeal and vocal fold contact dynamics occur between two professional voice populations (MT and OP) during singing tasks and (b) to determine if differences occur between MT and OP singers in oral configuration and associated acoustic resonance during singing tasks. Method Twenty-one singers (10 MT and 11 OP) were included. All participants were currently enrolled in a music program. Experimental procedures consisted of sustained phonation on the vowels /i/ and /ɑ/ during both a low-pitch task and a high-pitch task. Measures of hyolaryngeal elevation, tongue height, and tongue advancement were assessed using ultrasonography. Vocal fold contact dynamics were measured using electroglottography. Simultaneous acoustic recordings were obtained during all ultrasonography procedures for analysis of the first two formant frequencies. Results Significant oral configuration differences, reflected by measures of tongue height and tongue advancement, were seen between groups. Measures of acoustic resonance also showed significant differences between groups during specific tasks. Both singer groups significantly raised their hyoid position when singing high-pitched vowels, but hyoid elevation was not statistically different between groups. Likewise, vocal fold contact dynamics did not significantly differentiate the two singer groups. Conclusions These findings suggest that, under controlled phonation conditions, MT singers alter their oral configuration and achieve differing resultant formants as compared with OP singers. Because singers are at a high risk of developing a voice disorder, understanding how these two groups of singers adjust their vocal tract configuration during their specific singing genre may help to identify risky vocal behavior and provide a basis for prevention of voice disorders.

Identification of Diseases in Newborns Using Advanced Acoustic Features of Cry Signals

Our challenge in the current study is to extend research on the cries of newborns for the early diagnosis of different pathologies. This paper proposes a recognition system for healthy and pathological cries using a probabilistic neural network classifier. Two different kinds of features have been used to characterize newborn cry signals: 1) acoustic features such as fundamental frequency glide (F0glide) and resonance frequencies dysregulation (RFsdys); 2) conventional features such as mel-frequency cestrum coefficients. This paper describes the automatic estimation of the proposed characteristics and the performance evaluation of these features in identifying pathological cries. The adopted methods for F0glides and RFsdys estimation are based on the derived function of the F0 contour and the jump "J" of the RFs between two subsequent tunings, respectively. The database used contains 3250 cry samples of full-term and preterm newborns, and includes healthy and pathologic cries. The obtained results indicate the important association between the quantified features and some studied pathologies, and also an improvement in the identification of pathologic cries. The best result obtained is 88.71% for the correct identification of health status of preterm newborns, and 82% for the correct identification of full-term infants with a specific disease. We conclude that using the proposed characteristics improves the diagnosis of pathologies in newborns. Moreover, the method applied in the estimation of these characteristics allows us to extend this study to other uninvestigated pathologies.

An Acoustic Examination of Pitch Variation in Soprano Singing

INTRODUCTION

The ability to perform acoustic inspection of data and to correlate the results with perceptual and physiological aspects facilitates vocal behavior analysis. The singing voice has specific characteristics and parameters that are involved during the phonation mechanism, which may be analyzed acoustically.

OBJECTIVE

To describe and analyze the fundamental frequency and formants in pitch variation in the /a/ vowel in sopranos.

METHODS

The sample consisted of 30 female participants between the ages of 20 to 45 years without vocal complaints. All sustained vowel sounds were recorded with the /a/ vowel sustained for 5 seconds, with three replications at low (C4-261 Hz), medium (Eb4-622 Hz), and high (Bb4-932 Hz) frequencies that were comfortable for the voice classification. In total, 90 samples were analyzed with digital extraction of the fundamental frequency (f0) and the first five formants (F1, F2, F3, F4, and F5) and manual confirmation. The middle segment was considered for analysis, whereas the onset and offset segments were not considered. Subsequently, FFT (fast Fourier transform) plots, LPC (linear predictive coding) graphs, and tube diagrams were created. The Shapiro-Wilks test was applied for adherence and the Friedman test was applied for comparison of paired samples.

RESULTS

For vocalizations at low and medium pitches, higher values were observed for the first five formant frequencies than for the f0 value. Overlaying the LPC and FFT graphs revealed a similarity between F1 and F2 at the two pitches, with clustered harmonics in the F3, F4, and F5 region in the low pitch. At the medium pitch, there was similarity between F3 and F4, an F5 peak, and tuned harmonics. However, in the high-pitch vocalizations, there was an increase in the F2, F3, F4, and F5 values in relation to f0, and there was similarity between them along with synchrony between f0 and F1, H2 and F2, H3 and F3, H4 and F4, and H5 and F5.

CONCLUSIONS

Pitch changes indicate differences in the behavior of the fundamental frequency and sound formants in sopranos. The comparison of the sustained vowels sounds in f0 at the three pitches revealed specific vocal tract changes on the LPC curve and FFT harmonics, with an extra gain range at 261 Hz, synchrony between peaks of formants and harmonics at 622 Hz, and equivalence of f0 and F1 at 932 Hz.

Magnetic resonance imaging-based measurement of internal deformation of vibrating vocal fold models

A method is presented for tracking the internal deformation of self-oscillating vocal fold models using magnetic resonance imaging (MRI). Silicone models scaled to four times life-size to lower the flow-induced vibration frequency were embedded with fiducial markers in a coronal plane. Candidate marker materials were tested using static specimens, and two materials, cupric sulfate and glass, were chosen for testing in the vibrating vocal fold models. The vibrating models were imaged using a gated MRI protocol wherein MRI acquisition was triggered using the subglottal pressure signal. Two-dimensional image slices at different phases during self-oscillation were captured, and in each phase the fiducial markers were clearly visible. The process was also demonstrated using a three-dimensional scan at two phases. The benefit of averaging to increase signal-to-noise ratio was explored. The results demonstrate the ability to use MRI to acquire quantitative deformation data that could be used, for example, to validate computational models of flow-induced vocal fold vibration and quantify deformation fields encountered by cells in bioreactor studies.

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.

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.

Regional ventilation during phonation in professional male and female singers

The respiratory system is a central part of voice production, but details in breath control during phonation are not yet fully understood. This study therefore aims to investigate regional ventilation of the lungs during phonation. It was analyzed in 11 professional singers using electrical impedance tomography during breathing and phonation with maximum phonation time. Our results show differences in impedance changes between phonation and exhalation in the courses of time and amplitude normalized curves. Furthermore, differences related to gender and professionalism were found in the temporal and spatial profiles of regional ventilation. For female singers (sopranos and mezzo-sopranos) the anterior region participated less at the start of ventilation, and was more stable at the midpoint compared to male singers (tenors). This might be an expression of a smaller relative movement in rib cage and anterior diaphragm, primarily in early phonation.

Morphometric Differences of Vocal Tract Articulators in Different Loudness Conditions in Singing

Introduction

Dynamic MRI analysis of phonation has gathered interest in voice and speech physiology. However, there are limited data addressing the extent to which articulation is dependent on loudness.

Material and Methods

12 professional singer subjects of different voice classifications were analysed concerning the vocal tract profiles recorded with dynamic real-time MRI with 25fps in different pitch and loudness conditions. The subjects were asked to sing ascending scales on the vowel /a/ in three loudness conditions (comfortable = mf, very soft = pp, very loud = ff, respectively). Furthermore, fundamental frequency and sound pressure level were analysed from the simultaneously recorded optical audio signal after noise cancellation.

Results

The data show articulatory differences with respect to changes of both pitch and loudness. Here, lip opening and pharynx width were increased. While the vertical larynx position was rising with pitch it was lower for greater loudness. Especially, the lip opening and pharynx width were more strongly correlated with the sound pressure level than with pitch.

Conclusion

For the vowel /a/ loudness has an effect on articulation during singing which should be considered when articulatory vocal tract data are interpreted.

Comparison of Cartesian and Non-Cartesian Real-Time MRI Sequences at 1.5T to Assess Velar Motion and Velopharyngeal Closure during Speech

Dynamic imaging of the vocal tract using real-time MRI has been an active and growing area of research, having demonstrated great potential to become routinely performed in the clinical evaluation of speech and swallowing disorders. Although many technical advances have been made in regards to acquisition and reconstruction methodologies, there is still no consensus in best practice protocols. This study aims to compare Cartesian and non-Cartesian real-time MRI sequences, regarding image quality and temporal resolution trade-off, for dynamic speech imaging. Five subjects were imaged at 1.5T, while performing normal phonation, in order to assess velar motion and velopharyngeal closure. Data was acquired using both Cartesian and non-Cartesian (spiral and radial) real-time sequences at five different spatial-temporal resolution sets, between 10 fps (1.7×1.7×10 mm3) and 25 fps (1.5×1.5×10 mm3). Only standard scanning resources provided by the MRI scanner manufacturer were used to ensure easy applicability to clinical evaluation and reproducibility. Data sets were evaluated by comparing measurements of the velar structure, dynamic contrast-to-noise ratio and image quality visual scoring. Results showed that for all proposed sequences, FLASH spiral acquisitions provided higher contrast-to-noise ratio, up to a 170.34% increase at 20 fps, than equivalent bSSFP Cartesian acquisitions for the same spatial-temporal resolution. At higher frame rates (22 and 25 fps), spiral protocols were optimal and provided higher CNR and visual scoring than equivalent radial protocols. Comparison of dynamic imaging at 10 and 22 fps for radial and spiral acquisitions revealed no significant difference in CNR performance, thus indicating that temporal resolution can be doubled without compromising spatial resolution (1.9×1.9 mm2) or CNR. In summary, this study suggests that the use of FLASH spiral protocols should be preferred over bSSFP Cartesian for the dynamic imaging of velopharyngeal closure, as it allows for an improvement in CNR and overall image quality without compromising spatial-temporal resolution.

Recommendations for real-time speech MRI

Real-time magnetic resonance imaging (RT-MRI) is being increasingly used for speech and vocal production research studies. Several imaging protocols have emerged based on advances in RT-MRI acquisition, reconstruction, and audio-processing methods. This review summarizes the state-of-the-art, discusses technical considerations, and provides specific guidance for new groups entering this field. We provide recommendations for performing RT-MRI of the upper airway. This is a consensus statement stemming from the ISMRM-endorsed Speech MRI summit held in Los Angeles, February 2014. A major unmet need identified at the summit was the need for consensus on protocols that can be easily adapted by researchers equipped with conventional MRI systems. To this end, we provide a discussion of tradeoffs in RT-MRI in terms of acquisition requirements, a priori assumptions, artifacts, computational load, and performance for different speech tasks. We provide four recommended protocols and identify appropriate acquisition and reconstruction tools. We list pointers to open-source software that facilitate implementation. We conclude by discussing current open challenges in the methodological aspects of RT-MRI of speech.

Correlation Between the Position of the Hyoid Bone on Lateral Cephalographs and Formant Frequencies

OBJECTIVES

The objective of this study is to examine the F1, F2, F3, and F4 during sustained vowels /ɑ/, /i/, /o/, /u/.

STUDY DESIGN

Prospective cross-sectional study.

METHODS

Fifty-two consecutive patients aged between 9 years and 38 years were invited to participate in this study. Linear measurements included linear vertical distance from the hyoid bone to the sella turcica (H-S); linear vertical distance from the hyoid bone to the posterior nasal spine (H-PNS); linear measure from the hyoid bone to the most anterior point of the cervical vertebra C3 (H-C3); and linear vertical distance from the hyoid bone to the mandibular plane (H-MP).

RESULTS

The results showed a moderate and statistically significant correlation between the average fundamental frequency for the vowel /ɑ/ and H-C3, H-S, and H-PNS and another moderate negative correlation between F3 and F4, and the vertical position of the hyoid bone H-C3 and H-S. For the vowel /i/, there was a moderate negative correlation between F1, F3, and F4 and H-S and also a moderate negative correlation between F3 and F4 and H-C3. For the vowel /o/, there was a moderate negative correlation between F4 and H-S and H-PNS. For the vowel /u/, only F4 correlated significantly with H-S.

CONCLUSION

There is a moderate correlation between the high formants, mostly F4, and the cephalo-caudal position of the hyoid bone.

Lower Vocal Tract Morphologic Adjustments Are Relevant for Voice Timbre in Singing

The vocal tract shape is crucial to voice production. Its lower part seems particularly relevant for voice timbre. This study analyzes the detailed morphology of parts of the epilaryngeal tube and the hypopharynx for the sustained German vowels /a/, /e/, /i/, /o/, and /u/ by thirteen male singer subjects who were at the beginning of their academic singing studies. Analysis was based on two different phonatory conditions: a natural, speech-like phonation and a singing phonation, like in classical singing. 3D models of the vocal tract were derived from magnetic resonance imaging and compared with long-term average spectrum analysis of audio recordings from the same subjects. Comparison of singing to the speech-like phonation, which served as reference, showed significant adjustments of the lower vocal tract: an average lowering of the larynx by 8 mm and an increase of the hypopharyngeal cross-sectional area (+ 21.9%) and volume (+ 16.8%). Changes in the analyzed epilaryngeal portion of the vocal tract were not significant. Consequently, lower larynx-to-hypopharynx area and volume ratios were found in singing compared to the speech-like phonation. All evaluated measures of the lower vocal tract varied significantly with vowel quality. Acoustically, an increase of high frequency energy in singing correlated with a wider hypopharyngeal area. The findings offer an explanation how classical male singers might succeed in producing a voice timbre with increased high frequency energy, creating a singer‘s formant cluster.

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.

Weight-bearing MR imaging as an option in the study of gravitational effects on the vocal tract of untrained subjects in singing phonation

Magnetic Resonance Imaging (MRI) of subjects in a supine position can be used to evaluate the configuration of the vocal tract during phonation. However, studies of speech phonation have shown that gravity can affect vocal tract shape and bias measurements. This is one of the reasons that MRI studies of singing phonation have used professionally trained singers as subjects, because they are generally considered to be less affected by the supine body position and environmental distractions. A study of untrained singers might not only contribute to the understanding of intuitive singing function and aid the evaluation of potential hazards for vocal health, but also provide insights into the effect of the supine position on singers in general. In the present study, an open configuration 0.25 T MRI system with a rotatable examination bed was used to study the effect of body position in 20 vocally untrained subjects. The subjects were asked to sing sustained tones in both supine and upright body positions on different pitches and in different register conditions. Morphometric measurements were taken from the acquired images of a sagittal slice depicting the vocal tract. The analysis concerning the vocal tract configuration in the two body positions revealed differences in 5 out of 10 measured articulatory parameters. In the upright position the jaw was less protruded, the uvula was elongated, the larynx more tilted and the tongue was positioned more to the front of the mouth than in the supine position. The findings presented are in agreement with several studies on gravitational effects in speech phonation, but contrast with the results of a previous study on professional singers of our group where only minor differences between upright and supine body posture were observed. The present study demonstrates that imaging of the vocal tract using weight-bearing MR imaging is a feasible tool for the study of sustained phonation in singing for vocally untrained subjects.

Vocal tract resonances in singing: variation with laryngeal mechanism for male operatic singers in chest and falsetto registers

Seven male operatic singers sang the same notes and vowels in their chest and their falsetto registers, covering the overlap frequency range where two main laryngeal mechanisms can be identified by means of electroglottography: M1 in chest register and M2 in falsetto register. Glottal contact quotients determined using electroglottography were typically lower by 0.27 in M2 than in M1. Vocal tract resonance frequencies were measured by using broadband excitation at the lips and found to be typically lower in M2 than in M1 sung at the same pitch and vowel; R1 typically by 65 Hz and R2 by 90 Hz. These shifts in tract resonances were only weakly correlated with the changes in the contact quotient or laryngeal height that were measured simultaneously. There was considerable variability in the resonance tuning strategies used by the singers, and no evidence of a uniform systematic tuning strategy used by all singers. A simple model estimates that the shifts in resonance frequencies are consistent with the effective glottal area in falsetto register (M2) being 60%-70% of its value in chest register (M1).

Motor functions in trumpet playing-a real-time MRI analysis

INTRODUCTION

The function of the orofacial and pharyngeal musculature for sound generation in brass instruments is insufficiently investigated. The contribution of muscles defying direct observation remains poorly understood. Time-resolved magnetic resonance imaging (MRI) allows visualization of muscle function as well as changes of the oropharyngeal cavities during muscle activation.

METHODS

We used fast 3-T MRI imaging to analyze motor activation during sound generation in brass instruments. Twelve professional trumpeters were analyzed at different pitch, loudness and dynamic. MR images were analyzed for position of the mouthpiece to lips and teeth, pivoting, nasopharyngeal closure and changes in the area of oral and pharyngeal cavity.

RESULTS

Of the 12 subjects, eight positioned the mouthpiece mainly to the upper lip, three in equal parts to upper and lower lip, and only one mostly to the lower lip. The last turned out to be the only subject with upward pivoting. All subjects had a complete velopharyngeal closure. Measurements of the oral and pharyngeal cavities showed an increase when subjects were playing higher pitches. The increase in areas of oral and pharyngeal cavity was present also when switching from lower to higher loudness and when performing crescendo to decrescendo. Enlargement of the oral and pharyngeal cavity was less pronounced with increasing loudness. But no general difference in change of oral and pharyngeal cavity could be observed.

CONCLUSIONS

The present study shows that it is possible to measure motor function and its implications on oral as well as pharyngeal cavities during sound generation in brass instruments. These changes seem to follow a reproducible pattern.

Dynamic real-time magnetic resonance imaging for the analysis of voice physiology

PURPOSE OF REVIEW

For a number of years, it has been possible to use dynamic real-time magnetic resonance imaging (MRI) to analyse the dynamic processes which occur in the human body. In the fields of laryngology and phoniatrics, such dynamic processes are found not only in swallowing, but also in voice and speech production. This article aims to present an overview of how the use of MRI might add to our current understanding of the dynamic processes involved in voice production.

RECENT FINDINGS

It is shown that up to now the analysis of vocal fold oscillations has been limited by MRI's relatively low sampling rate of up to 50 Hz. Nevertheless, more detailed analysis does seem possible with regard to the modulation of the power source and vocal tract.

SUMMARY

Dynamic real-time MRI offers a great opportunity for the analysis of voice production in all stages of the voice production system.

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.

[Medical treatment of singers' voices]

ENT/phoniatrics specialists are frequently the primary reference persons for patients who have problems with the professional use of their voice. Singers show the highest risk factors for voice disorders among all professional voice users. The treatment and care of singers requires specific knowledge and competence of the physician, as well as a treatment setting adapted to the needs of this special group of patients, whose existence depends on the use of their voice. To some extent, evidence based concepts can be taken into account when treating professional singers. In cases for which no concepts have yet been developed and evaluated, recourse to clinical experience is necessary. In the present paper, current concepts for the treatment of singers are discussed on the basis of scientific publications and on long-standing experience of consultations in musician's medicine and ENT, under the aspects of diagnosis, therapy as well as prevention, taking into account the most frequent voice problems in professional singers.

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 area functions and formant frequencies in opera tenors' modal and falsetto registers

According to recent model investigations, vocal tract resonance is relevant to vocal registers. However, no experimental corroboration of this claim has been published so far. In the present investigation, ten professional tenors' vocal tract configurations were analyzed using MRI volumetry. All subjects produced a sustained tone on the pitch F4 (349 Hz) on the vowel /a/ (1) in modal and (2) in falsetto register. The area functions were estimated from the MRI data and their associated formant frequencies were calculated. In a second condition the same subjects repeated the same tasks in a sound treated room and their formant frequencies were estimated by means of inverse filtering. In both recordings similar formant frequencies were observed. Vocal tract shapes differed between modal and falsetto register. In modal as compared to falsetto the lip opening and the oral cavity were wider and the first formant frequency was higher. In this sense the presented results are in agreement with the claim that the formant frequencies differ between registers.

Membranous and cartilaginous vocal fold adduction in singing

While vocal fold adduction is an important parameter in speech, relatively little has been known on the adjustment of the vocal fold adduction in singing. This study investigates the possibility of separate adjustments of cartilaginous and membranous vocal fold adduction in singing. Six female and seven male subjects, singers and non-singers, were asked to imitate an instructor in producing four phonation types: "aBducted falsetto" (FaB), "aDducted falsetto" (FaD), "aBducted Chest" (CaB), and "aDducted Chest" (CaD). The phonations were evaluated using videostroboscopy, videokymography (VKG), electroglottography (EGG), and audio recordings. All the subjects showed less posterior (cartilaginous) vocal fold adduction in phonation types FaB and CaB than in FaD and CaD, and less membranous vocal fold adduction (smaller closed quotient) in FaB and FaD than in CaB and CaD. The findings indicate that the exercises enabled the singers to separately manipulate (a) cartilaginous adduction and (b) membranous medialization of the glottis though vocal fold bulging. Membranous adduction (monitored via videokymographic closed quotient) was influenced by both membranous medialization and cartilaginous adduction. Individual control over these types of vocal fold adjustments allows singers to create different vocal timbres.