The Effect of Singers' Masks on the Impulse Dispersion of Aerosols During Singing

BACKGROUND

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.

MATERIAL AND METHODS

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.

RESULTS

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.

CONCLUSION

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.

Boys Choirs in the Pandemic: Effects of Distance and Other Factors on Spectral and Temporal Accuracy

During the Covid-19 pandemic, choral singing has been either completely prohibited or regulated with safety measures due to increased transmission risks. However, the impact of larger inter-singer spacings on the performance and educational process in boys' choirs is unclear. This study analyzed recordings of six groups of five singers each from two boys' choirs aged 7-16 who sang Beethoven's Ode to Joy while standing on an arc with a 4 m radius and an inter-subject spacing of 0.5-3 m. The effects of singers' masks, distance, group age, and relative position on the timing of articulation and fundamental frequency were investigated, along with the amount, rate, and sign of pitch drift and loudness. The ANOCOVA results showed that onsets were robust to the tested factors, while errors in fundamental frequency tended to decrease with increasing age/experience. Loudness was affected by distance, mask, and relative position, with increasing loudness as spacing decreased. Understanding influencing factors can inform recommendations for choral singing and education.

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.

Boys Choirs in the Pandemic: Exploring Qualitative Aspects of Safety Measures

INTRODUCTION

During the Covid-19 pandemic, choirs had to apply safety measures such as distances and wearing masks. For children's choirs, there is no knowledge of their reaction to these measures, regarding their age and experience. This study aimed to investigate boys choir singers' perceptions of the measures, regarding wellbeing and feasibility, as well as the quality of the performance outcomes.

METHODS

Six groups were put together, assembling five singers of the same age (7-16 years, before voice change) and experience level. The boys sang one verse of the same song at inter-subject distances of 3, 1.5, 0.5, 0.5 m plus wearing a mask and again 3 m. Afterward they filled out questionnaires concerning difficulty, irritation, hearing themselves and their neighbors, and if they could imagine singing regularly in the respective setting. Fifteen parents were asked to fill out questionnaires about their opinions about choir safety measures during the pandemic. Six anonymous boys choir experts rated the randomized recordings of all tasks regarding homogenous sound quality, rhythmical precision, and uniform intonation.

RESULTS

Even though most of the children preferred smaller distances, they were open to all kinds of settings. The answers given were very specific to the individuals. Masks were voted out by a majority of the subjects. Parents found choir singing very important for their children and did in majority neither fear infection of their children, nor mind precautions. The experts rated the performance outcomes of the largest distance (3 m) as best in most of the cases.

CONCLUSION

Different interspatial settings do not harm the children and adolescents and could be introduced as a beneficial approach to give them a broader listening experience and to make them flexible, alert, adaptable, and resilient singers. Singers' masks are only recommended for compelling circumstances.

Impulse dispersion of aerosols during playing the recorder and evaluation of safety measures

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.

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.

Are source-filter interactions detectable in classical singing during vowel glides?

In recent studies, it has been assumed that vocal tract formants (F_n) and the voice source could interact. However, there are only few studies analyzing this assumption in vivo. Here, the vowel transition /i/-/a/-/u/-/i/ of 12 professional classical singers (6 females, 6 males) when phonating on the pitch D4 [fundamental frequency (ƒ_o) ca. 294 Hz] were analyzed using transnasal high speed videoendoscopy (20.000 fps), electroglottography (EGG), and audio recordings. F_n data were calculated using a cepstral method. Source-filter interaction candidates (SFICs) were determined by (a) algorithmic detection of major intersections of F_n/nƒ_o and (b) perceptual assessment of the EGG signal. Although the open quotient showed some increase for the /i-a/ and /u-i/ transitions, there were no clear effects at the expected F_n/nƒ_o intersections. In contrast, ƒ_o adjustments and changes in the phonovibrogram occurred at perceptually derived SFICs, suggesting level-two interactions. In some cases, these were constituted by intersections between higher nƒ_o and F_n. The presented data partially corroborates that vowel transitions may result in level-two interactions also in professional singers. However, the lack of systematically detectable effects suggests either the absence of a strong interaction or existence of confounding factors, which may potentially counterbalance the level-two-interactions.

Sources of Aerosol Dispersion During Singing and Potential Safety Procedures for Singers

INTRODUCTION

With respect to the Covid-19 pandemic, singing is assumed to be associated with a high potential person-to-person transmission. However, it remains unclear how the impulse dispersion varies with different types of articulation, intensity levels of diction, or body position. Furthermore, it has not been understood in detail how to prevent aerosol dispersion during singing.

MATERIAL AND METHODS

Single professional singers from the Bavarian Radio Chorus were asked to sing in different head positions, with different articulation patterns and different masks after inhaling the basic liquid of an e-cigarette. The vapor cloud was segmented and tracked over time.

RESULTS

Consonants and exaggeration of diction enhanced the distance reached by the impulse dispersion. Furthermore, the greatest dispersion was reached for a neutral head position. All protection masks stopped the initial jet of the aerosols but the FFP2 masks were the most effective.

CONCLUSION

Some protection equipment has been identified to be promising in reducing aerosol dispersion. However, systematic effects have to be evaluated in greater collectives.

Vocal fold oscillation pattern changes related to loudness in patients with vocal fold mass lesions

Introduction

Vocal fold mass lesions can affect vocal fold oscillation patterns and therefore voice production. It has been previously observed that perturbation values from audio signals were lower with increased loudness. However, how much the oscillation patterns change with gradual alteration of loudness is not yet fully understood.

Material and methods

Eight patients with vocal fold mass lesions were asked to perform a glide from minimum to maximum loudness on the vowel /i/, ƒ_o of 125 Hz for male or 250 Hz for female voices. During phonation the subjects were simultaneously recorded with transnasal high speed videoendoscopy (HSV, 20,000 fps), electroglottography (EGG), and an audio recording. Based on the HSV material the Glottal Area Waveform (GAW) was segmented and GAW parameters were computed.

Results

The greatest vocal fold irregularities were observed at different values between minimum and maximum sound pressure level. There was a relevant discrepancy between the HSV and EGG derived open quotients. Furthermore, the EGG derived sample entropy and GAW values also evidenced different behavior.

Conclusions

The amount of vocal fold irregularity changes with varying loudness. Therefore, any evaluation of the voice should be performed under different loudness conditions. The discrepancy between EGG and GAW values appears to be much stronger in patients with vocal fold mass lesions than those with normal physiological conditions.

Level of evidence

4.

Duration of biodynamic changes associated with water resistance therapy

INTRODUCTION

In current voice research, there is a growing interest in semi-occluded vocal tract exercises and their contribution to an increased vocal efficiency. However, there are only few studies on the lasting effects.

MATERIAL AND METHODS

Eight vocally healthy subjects were asked to sustain a phonation at a comfortable loudness on the vowel /i/, with a Fundamental Frequency of 250 Hz (females) or 125 Hz (males). During phonation the subjects were simultaneously recorded with transnasal High Speed Videoendoscopy (HSV, 20,000fps), electroglottography, and audio signals. The subjects then performed a water resistance therapy (WRT) for 10 min (tube: 30 cm length, 5 cm below water surface, diameter 9 mm). Repeated measurements of sustained phonation were performed 0, 5, 10, 20, and 30 min after exercising. From the HSV material the Glottal Area Waveform (GAW) was segmented and GAW parameters were computed.

RESULTS

There were strong inter-individual differences concerning the changes of different measures over time after WRT. In general, directly after WRT there was a lowering of the GAW derived Period Perturbation Quotient, a lowering of the Closing Quotient and an increase of the Sound Pressure Level (SPL) in comparison to the pre-intervention measurement. However, only 5 min post WRT there was no longer a clear difference compared to baseline results before WRT. Other values such as Open Quotients exhibited no evident changes by WRT at any timepoint.

CONCLUSIONS

WRT showed strong inter-individual effects concerning the changes in the evaluated measures post-intervention. General tendencies of some measures directly after the intervention showed a brief effect of only a few minutes.

The Effect of Nasalance on Vocal Fold Oscillation Patterns During the Male Passaggio

INTRODUCTION

It is generally assumed that when singing across the region where registration events for untrained voices occur (the passaggio), singers modify the voice production system in order to avoid changes of voice quality. In this context, it has been postulated that nasalance could be used to stabilize vocal function throughout the passaggio. However, whether nasalance is frequently used by professional singers and if so, if it has a stabilizing effect on vocal fold oscillation patterns, is not yet fully understood.

MATERIAL AND METHODS

Eight western classically trained professional male singers (6 tenors and 2 baritones) were asked to perform transitions (1) from modal to falsetto register and (2) from modal to stage voice above the passaggio (SVaP) during ascending pitch glides from A3 (ƒo approx. 220 Hz) to A4 (ƒo approx. 440 Hz) on the vowel /i/. Transnasal high-speed videoendoscopy at 20.000 fps was captured simultaneously with electroglottographic, nasal and oral flow, and audio signals, recorded using the same frame rate. The nasalance was calculated from both oral and nasal DC-flow signals.

RESULTS

Transitions to SVaP showed greater periodicity and regularity than transitions to falsetto. For 5 subjects, nasalance was increased during the passaggio for the transition to SVaP. For 4 subjects the increase of nasalance for the SVaP was associated with a stabilization of the open quotient and occurred at a comparable fundamental frequency as the increase of the open quotient for the transition to falsetto.

CONCLUSIONS

Nasalance can be used in order to stabilize oscillatory regularity and open quotient in male singers for singing across the passaggio.

A comparison of electroglottographic and glottal area waveforms for phonation type differentiation in male professional singers

This study compares the use of electroglottograms (EGGs) and glottal area waveforms (GAWs) to study phonation in different vibratory states as produced by professionally trained singers. Six western classical tenors were asked to phonate pitch glides from modal to falsetto phonation, or from modal to their stage voice above the passaggio (SVaP). For each pitch glide the sample entropy (SampEn) of the EGG signal was calculated to detect the occurrence of phonatory instabilities and establish a "ground truth" for the performed phonation type. The cycles before the maximum SampEn were labeled as modal, and the cycles after the peak were labeled as either falsetto, or SVaP. Three automatic categorizations of vibratory state were performed using clustering: one based only on the EGG, one based on the GAW, and one based on their combination. The error rate (clustering vs ground truth) was, on average, lower than 10% for all of the three settings, revealing no special advantage of the GAW over EGG, and vice versa. Modal voice cycles exhibited a larger contact quotient, larger normalized derivative peak ratio, and lower rise time, compared to SVaP and falsetto. The GAW-based normalized maximum area declination rate was larger in SVaP compared to modal voice.

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.

Codon usage as a reason for unsuccessful search for amber-suppressor mutants in Streptomyces lividans?

An amber mutation was created in the CAT gene of plasmid vector pACYC184 and this modified plasmid was fused with theStreptomycesvector pIJ702 for use as an indicator for the identification ofStreptomycesstrains carrying nonsense suppressor tRNA mutations. The resulting hybrid plasmid pGM1109 was introduced into the chloramphenicol-sensitive mutant M252 ofStreptomyces lividans. Chloramphenicol-resistant colonies were isolated and characterized. None of them was a nonsense suppressor mutant. The failure to obtain such mutants is discussed on the basis of codon usage in streptomycetes.