During the Covid-19 pandemic, singing activities were restricted due to several super-spreading events that have been observed during rehearsals and vocal performances. However, it has not been clarified how the aerosol dispersion, which has been assumed to be the leading transmission factor, could be reduced by masks which are specially designed for singers. Twelve professional singers (10 of the Bavarian Radio-Chorus and two freelancers, seven females and five males) were asked to sing the melody of the ode of joy of Beethoven's 9th symphony "Freude schöner Götterfunken, Tochter aus Elisium" in D-major without masks and afterwards with five different singers' masks, all distinctive in their material and proportions. Every task was conducted after inhaling the basic liquid from an e-cigarette. The aerosol dispersion was recorded by three high-definition video cameras during and after the task. The cloud was segmented and the dispersion was analyzed for all three spatial dimensions. Further, the subjects were asked to rate the practicability of wearing the tested masks during singing activities using a questionnaire. Concerning the median distances of dispersion, all masks were able to decrease the impulse dispersion of the aerosols to the front. In contrast, the dispersion to the sides and to the top was increased. The evaluation revealed that most of the subjects would reject performing a concert with any of the masks. Although, the results exhibit that the tested masks could be able to reduce the radius of aerosol expulsion for virus-laden aerosol particles, there are more improvements necessary to enable the practical implementations for professional singing.

The human voice exhibits diverse expressions, primarily generated by the regular oscillatory movement of both vocal folds. However, further vocal tract structures can also oscillate, as observed in different singing styles, supraglottic voice substitutes and functional voice disorders. To describe the spectrum of irregular phonation types from a nonlinear systems perspective, we conducted in vivo investigations with a professional metal singer using transnasal high-speed digital imaging combined with electroglottography and acoustic data. Here, we analysed 10 distinct voice qualities. Some of these show oscillatory mechanisms characterized by nearly periodic patterns that differ in three key aspects: the ratio of glottal to supraglottic oscillations, their behaviour during the glissando and the oscillating structures primarily involved. Both reduced glottal adduction and increased glottal and supraglottic compression contribute to a greater degree of irregularity. The supraglottic oscillations can coexist with various glottal oscillation mechanisms. Based on the in vivo data, we identified various nonlinear phenomena of different categories that include synchronized oscillations with defined frequency ratios, bifurcations, biphonations and chaotic oscillations.

Introduction: Group musical activities using wind instruments have been restricted during the CoVID19 pandemic due to suspected higher risk of virus transmission. It was presumed that the aerosols exhaled through the tubes while playing would be ejected over larger distances and spread into the room due to jet stream effects. In particular, the soprano recorder is widely used as an instrument in school classes, for beginners of all age groups in their musical education, in the context of leisure activities and in professional concert performances. Understanding the aerosol impulse dispersion characteristics of playing the soprano recorder could assist with the establishment of concepts for safe music-making. Methods: Five adult professionally trained soprano recorder players (4 female, 1 male) played four bars of the main theme of L. van Beethoven’s “Ode to Joy” in low and in high octaves, as well as with 3 different potential protection devices in the high octave. For comparison they spoke the corresponding text by F. Schiller. Before each task, they inhaled .5 L of vapor from an e-cigarette filled with base liquid. The vapor cloud escaping during speaking or playing was recorded by cameras and its spread was measured as a function of time in the three spatial dimensions. The potential safety devices were rated for practicability with a questionnaire, and their influence on the sound was compared, generating a long-term average spectrum from the audio data. Results: When playing in the high octave, at the end of the task the clouds showed a median distance of 1.06 m to the front and .57 m diameter laterally (maxima: x: 1.35 m and y: .97 m). It was found that the clouds’ expansion values in playing the recorder with and without safety measures are mostly lower when compared to the ordinary, raised speaking voice of the same subjects. The safety devices which covered the instrument did not show clear advantages and were rated as unpractical by the subjects. The most effective reduction of the cloud was reached when playing into a suction funnel. Conclusion: The aerosol dispersion characteristics of soprano recorders seem comparable to clarinets. The tested safety devices which covered holes of the instrument did not show clear benefits.

In voice production, interactions occur between the oscillating vocal folds, the respiratory system, and the vocal tract. However, it is not yet sufficiently understood how the respiratory system could affect the vocal tract configuration. It is hypothesized that a reduction in tracheal pull, caused by decreasing lung volume, along with shifts in dominant exhalation forces (from inspiratory to expiratory muscles), leads to a larynx elevation with shortening of the vocal tract tube, and consecutively, articulatory adjustments to preserve consistent sound quality. Seventeen professional operatic singers performed a maximum phonation time task on comfortable pitch while being recorded with dynamic 2D-magnetic resonance imaging (MRI) (25 fps, pixel resolution of 1.6 x 1.6 mm²) including simultaneous audio recording. From the MRI footage, articulatory movements were calculated for vertical larynx position, pharynx width at the narrowest point, lip opening, jaw opening, and jaw protrusion. Spectral data were extracted from the audio signals after noise reduction. The larynx moved in cranial direction in 5 of 9 female and 3 of 8 male participants during the phonatory exhalation. Such movement was directly counteracted by other articulators in four cases. In 12 of the subjects, articulatory and/or spectral events in the form of adaptions or twitches occurred around and after 50% of the phonation time. Most subjects exhibited changes in articulator positioning as well as adjustments to the subsequently sustained fundamental frequency during the first and last 10% of the sustained phonation. The articulatory movements during the task were non-systematic. Sudden events/adaptations in the second half of the phonatory exhalation could potentially mark a passage of the REL. The cranial movement of the larynx could be attributed to the decreasing tracheal pull; however, this was not evident in all subjects, suggesting a high degree of individuality in the regulation of respiratory movement in relation to vertical larynx position. Overall, the data indicate that it is important to consider continuous and sudden articulatory movements during sustained measurements.

This study aimed to characterize the biomechanics of vibrato and non-vibrato phonation in professional singers, focusing on vocal fold oscillation patterns and cuneiform cartilage movements. Ten vocally healthy, professionally-trained, western classical singers were instructed to sustain the vowel [i:] without vibrato, with vibrato, and again without vibrato, for approximately two seconds for each quality. Data were collected via acoustic recordings, electroglottography (EGG), and transnasal high-speed videoendoscopy. After segmentation, glottal area waveforms (GAW) were analyzed, and temporal trajectories of fundamental frequency ( fo) and glottal parameters were compared. Cuneiform cartilage movement was tracked in three spatial dimensions using the videoendoscopic image sequences. The participants maintained a relatively stable mean fo across conditions, with no significant differences in open quotient (OQEGG and OQGAW) and closing quotient (ClQ) regarding vibrato and non-vibrato. During vibrato, most participants showed a higher OQ in vibrato fo minima than in maxima. Vibrato was associated with lower cepstral peak prominence and higher sound pressure level (SPL), and SPL courses inverse to fo modulation. The cuneiform tubercle tracking correlated to fo showed vertical and horizontal movements which followed, in one subject, an epiglottis forward positioning, presumably due to a tilting by cricothyroid muscle activity linked to the vibrato phenomenon.