Respiratory and glottal efficiency measures in normal classically trained singers

Flow-induced oscillations of vocal-fold replicas with tuned extensibility and material properties

Human vocal folds are highly deformable non-linear oscillators. During phonation, they stretch up to 50% under the complex action of laryngeal muscles. Exploring the fluid/structure/acoustic interactions on a human-scale replica to study the role of the laryngeal muscles remains a challenge. For that purpose, we designed a novel in vitro testbed to control vocal-folds pre-phonatory deformation. The testbed was used to study the vibration and the sound production of vocal-fold replicas made of (i) silicone elastomers commonly used in voice research and (ii) a gelatin-based hydrogel we recently optimized to approximate the mechanics of vocal folds during finite strains under tension, compression and shear loadings. The geometrical and mechanical parameters measured during the experiments emphasized the effect of the vocal-fold material and pre-stretch on the vibration patterns and sounds. In particular, increasing the material stiffness increases glottal flow resistance, subglottal pressure required to sustain oscillations and vibratory fundamental frequency. In addition, although the hydrogel vocal folds only oscillate at low frequencies (close to 60 Hz), the subglottal pressure they require for that purpose is realistic (within the range 0.5-2 kPa), as well as their glottal opening and contact during a vibration cycle. The results also evidence the effect of adhesion forces on vibration and sound production.

The physiology of singing and implications for 'Singing for Lung Health' as a therapy for individuals with chronic obstructive pulmonary disease

Singing is an increasingly popular activity for people with chronic obstructive pulmonary disease (COPD). Research to date suggests that ‘Singing for Lung Health’ may improve various health measures, including health-related quality-of-life. Singing and breathing are closely linked processes affecting one another. In this narrative review, we explore the physiological rationale for ‘Singing for Lung Health’ as an intervention, focusing on the abnormalities of pulmonary mechanics seen in COPD and how these might be impacted by singing. The potential beneficial physiological mechanisms outlined here require further in-depth evaluation.

Respiratory Function and Voice: The Role for Airflow Measures

OBJECTIVE

To clarify the relationship between voice and respiratory function, and to understand the role for airflow measures in the evaluation of voice patients.

METHODS

Literature searches of MEDLINE (Ovid) and Web of Science were performed on April 6, 2020, to include articles written in English that both discussed voice in relation to lower respiratory function and reported evaluation of airflow. Search strategies included the keywords voice, respiratory, airflow, and aerodynamic measures. Data were extracted from articles that met inclusion criteria.

RESULTS

Twenty studies were included for review. Fourteen (70%) studies evaluated at least 1 spirometric respiratory measure, including Forced Vital Capacity, Forced Expiratory Volume in 1 second, and Forced Expiratory Flow. Other measures assessed included mean flow rate, mean peak airflow, phonatory airflow, inspiratory airflow, expiratory airflow, and phonation quotient. Notably, four studies which included pulmonary function tests (PFTs) as part of voice evaluation discovered previously undiagnosed respiratory disease in their study populations.

CONCLUSION

This review confirms that respiratory function contributes significantly to voice and reveals that few studies have explored the role for airflow measures in clarifying this relationship. Including airflow measures such as PFTs in standard voice evaluation may allow recognition of underlying respiratory disease contributing to voice dysfunction. Further research is recommended to establish indications and diagnostic criteria for the use of PFTs in voice patients.

The Role of the Pelvic Floor in Respiration: A Multidisciplinary Literature Review

OBJECTIVE

To conduct an interdisciplinary literature review on the function of the pelvic floor musculature during respiration and its role in phonation, particularly singing.

STUDY DESIGN

This is a literature review.

METHODS

A literature review was conducted using three electronic databases: PubMed, Scopus, and Google Scholar. An index search was also performed for the NATS Journal/Journal of Singing utilizing the keywords from the original search, as these articles did not appear in the original search. Peer-reviewed articles from 1985 to 2017 were gathered on the respiratory musculature and/or support mechanisms for phonation (anatomy and physiology). Articles that pertained to the muscular function of the respiratory system in breathing and/or phonation were utilized in the review. Eighty-five articles were included in this review.

RESULTS

Breathing and support strategies were variable and nonspecific in much of the singing voice literature. The voice science literature was a rich source of articles written about breathing and support for singing. Multiple studies looked at musculature utilized in respiration and breath support and subglottal pressure generation for muscular support. However, little or no mention was made specifically of the pelvic floor. The physical medicine literature includes the pelvic floor musculature as having an important role in respiration, as a key player in the generation of intra-abdominal pressure, and as a primary expiratory muscle.

CONCLUSIONS

The information gleaned from this literature review suggests that a cross-pollination between areas of science is needed, because quite obviously, the pelvic floor is a topic in physical medicine, but it is not (so much) in the voice literature. Reaching a consensus on how we describe the function of the respiratory musculature and specifically including the role of the pelvic floor in respiration and phonation deserves future attention. Further research looking specifically at the role of the pelvic floor in phonation is also warranted.

Medidas acústicas e aerodinâmicas em cantores: comparação entre homens e mulheres

RESUMO Objetivo Comparar medidas acústicas e aerodinâmicas da voz em homens e mulheres cantores. Método Trata-se de um estudo transversal, observacional, comparativo, com amostra de conveniência. Participaram do estudo 30 homens e 30 mulheres cantores. Foi realizada avaliação das medidas acústicas (intensidade e frequência fundamental) e aerodinâmicas (tempo de expiração, pressão aérea, fluxo de ar expirado e vozeado, volume expiratório, potência e resistência aerodinâmica, impedância acústica e eficiência aerodinâmica) durante a emissão da sílaba /pá/ em frequência e intensidade habituais, sete vezes consecutivas. Estas emissões permitem a extração de medidas de pressão aérea (obtidas da consoante plosiva /p/ que estima a pressão glótica) e das medidas de fluxo aéreo e acústicas da voz (obtidas da vogal /a/ da sílaba /pá/). Resultados Na comparação de homens e mulheres cantores, as mulheres apresentam maiores valores de frequência fundamental, e não houve diferenças na avaliação de valores das medidas aerodinâmicas entre os gêneros. Conclusão Os valores das medidas aerodinâmicas não se diferenciam entre mulheres e homens cantores.

The Utility of Pulmonary Function Testing in Patients Presenting With Dysphonia

OBJECTIVE

We aimed to evaluate the utility of pulmonary function testing (PFT), particularly forced expiratory flow (FEF) 25-75%, in patients presenting with dysphonia.

STUDY DESIGN

A retrospective chart review was carried out.

METHODS

Records of 199 patients who presented with dysphonia were reviewed to determine whether in-office PFTs, which we perform routinely, lead to new pulmonary diagnoses or the need for additional pulmonary medications, after assessment by a pulmonologist. Of particular interest was evaluating if FEF25-75% of predicted values less than 80% can be used as a marker for occult pulmonary disease in patients presenting with dysphonia.

RESULTS

Of the 199 patient charts reviewed, 129 were female and 70 were male. The age of patients ranged from 18 to 88 years, with a mean of 46.8 years. The body mass index ranged from 17.5 to 53.4 kg/m². One hundred five (52.8%) patients had FEF25-75% values less than 80% of predicted (poor midflow values). Of these patients, 76 (72.4%) were referred to a pulmonologist, 22 of 76 (28.9%) completed the referral, and 17 of 22 (77.3%) received a new pulmonary diagnosis or change in medications. Of the 155 patients without a history of pulmonary disease, 76 had poor midflow values, 57 (75%) of these patients were referred, and 12 of 57 (21%) completed the referral. Eight (67%) of these 12 patients were diagnosed with a previously unrecognized pulmonary disorder. Of the 44 patients with a prior history of pulmonary disease, 29 (65.9%) had poor midflow values. Nineteen (65.5%) of these patients were referred, and 9 (47%) received a new pulmonary diagnosis or a change in their medications. There were 51 classically trained singers and 148 nonclassically trained singers or nonsingers. There was no significant difference in average midflow values between the two groups (80.96 ± 24.7 and 80.73 ± 28.4, respectively) or in the percentage of classically trained singers with poor midflow values compared with nonsingers (53.5% vs. 49%, respectively).

CONCLUSION

This study suggests that patients with dysphonia may have unrecognized underlying pulmonary disease, and PFT should be considered as part of the routine initial voice evaluation for patients presenting with dysphonia.

Quantifying Laryngopharyngeal Reflux in Singers: Perceptual and Objective Findings

This study examines the relationship between laryngopharyngeal reflux (LPR) symptoms and oropharyngeal pH levels in singers. We hypothesized that reported symptoms would correlate with objective measures of pH levels from the oropharynx, including the number and total duration of reflux episodes. Twenty professional/semiprofessional singers completed the Reflux Symptom Index (RSI) and underwent oropharyngeal pH monitoring. Mild, moderate, or severe pH exposure was recorded during oropharyngeal pH monitoring. Correlations were performed to examine potential relationships between reflux symptoms and duration of LPR episodes. Symptom severity did not correlate with pH levels; however, we found a number of covariances of interest. Large sample sizes are necessary to determine if true correlations exist. Our results suggest that singers may exhibit enhanced sensitivity to LPR and may therefore manifest symptoms, even in response to subtle changes in pH. This study emphasizes the importance of sensitive and objective measures of reflux severity as well as consideration of the cumulative time of reflux exposure in addition to the number of reflux episodes.

A Review of the Physiological Effects and Mechanisms of Singing

Daily experience suggests that singing can energize us and even provide a physical workout. A growing amount of evidence has been presented to support anecdotal claims of the benefits of singing on health and well-being. Singing has been shown to be related to numerous physiological changes. The cardiorespiratory system is utilized during persistent singing training, resulting in enhanced respiratory muscles and an optimized breathing mode. In addition, singing can also cause changes in neurotransmitters and hormones, including the upregulation of oxytocin, immunoglobulin A, and endorphins, which improves immune function and increases feelings of happiness. This review is organized by respiratory, circulatory, and hormonal changes that are collectively a part of singing in a healthy population. The various studies are discussed with the intention of helping researchers and clinicians realize the potential benefit of singing and provide a clinical option as an adjunct therapy for a given situation. Better understanding of physiological mechanisms will lay a solid theoretical foundation for singing activities and will present important implications for further study. Evaluations of existing research and recommendations for future research are given to promote the scale and duration to better demonstrate the effectiveness of singing before it can be recommended in clinical guidelines and satisfy criteria for funding by commissioners of health and social care.

Comparison of Fundamental Frequency Nasalance between Trained Singers and Nonsingers for Sung Vowels

Objectives:

The purpose of this study was to determine the effect of vocal training on fundamental frequency nasalance measures under selected vowel and frequency conditions.

Methods:

Fundamental frequency nasalance measures were reported for 2 groups of women: 36 trained singers and 36 nonsingers. Each group sang and sustained the vowels (/i/, /æ/, /u/, /a/) for 6 seconds' duration at 3 frequency levels. A 3-second segment from the middle of each vowel was measured to generate fundamental frequency nasalance scores.

Results:

No significant differences were found in the mean fundamental frequency nasalance scores between the trained singers and the nonsingers. The fundamental frequency nasalance scores were significantly higher for front vowels for both groups. Additionally, both groups displayed a pattern of producing significantly higher fundamental frequency nasalance scores at lower fundamental frequencies than at higher fundamental frequencies.

Conclusions:

These findings support the practice of training singers to elevate the velum when singing at high frequencies but not when singing at low ones.

Breathing and Singing: Objective Characterization of Breathing Patterns in Classical Singers

Singing involves distinct respiratory kinematics (i.e. movements of rib cage and abdomen) to quiet breathing because of different demands on the respiratory system. Professional classical singers often advocate for the advantages of an active control of the abdomen on singing performance. This is presumed to prevent shortening of the diaphragm, elevate the rib cage, and thus promote efficient generation of subglottal pressure during phonation. However, few studies have investigated these patterns quantitatively and inter-subject variability has hindered the identification of stereotypical patterns of respiratory kinematics. Here, seven professional classical singers and four untrained individuals were assessed during quiet breathing, and when singing both a standard song and a piece of choice. Several parameters were extracted from respiratory kinematics and airflow, and principal component analysis was used to identify typical patterns of respiratory kinematics. No group differences were observed during quiet breathing. During singing, both groups adapted to rhythmical constraints with decreased time of inspiration and increased peak airflow. In contrast to untrained individuals, classical singers used greater percentage of abdominal contribution to lung volume during singing and greater asynchrony between movements of rib cage and abdomen. Classical singers substantially altered the coordination of rib cage and abdomen during singing from that used for quiet breathing. Despite variations between participants, principal component analysis revealed consistent pre-phonatory inward movements of the abdominal wall during singing. This contrasted with untrained individuals, who demonstrated synchronous respiratory movements during all tasks. The inward abdominal movements observed in classical singers elevates intra-abdominal pressure and may increase the length and the pressure-generating capacity of rib cage expiratory muscles for potential improvements in voice quality.

Acoustic Properties of the Voice Source and the Vocal Tract: Are They Perceptually Independent?

OBJECTIVE/HYPOTHESIS

This study sought to determine whether the properties of the voice source and vocal tract are perceptually independent.

STUDY DESIGN

Within-subjects design.

METHODS

This study employed a paired-comparison paradigm where listeners heard synthetic voices and rated them as same or different using a visual analog scale. Stimuli were synthesized using three different source slopes and two different formant patterns (mezzo-soprano and soprano) on the vowel /a/ at four pitches: A3, C4, B4, and F5.

RESULTS

Whereas formant pattern was the strongest effect, difference in source slope also affected perceived quality difference. Source slope and formant pattern were not independently perceived.

CONCLUSION

These results suggest that when judging laryngeal adduction using perceptual information, judgments may not be accurate when the stimuli are of differing formant patterns.

Comparison of dysphonia severity index between younger and older carnatic classical singers and nonsingers

OBJECTIVES

The main objective of this study was to compare dysphonia severity index (DSI) and its parameters between Carnatic classical singers and nonsingers. The second objective was to investigate the effect of age on DSI and its parameters in both singers and nonsingers.

STUDY DESIGN

This study included 30 female Carnatic classical singers who were subdivided into two groups based on their age: 15 younger singers and 15 older singers. These 30 singers were compared with 30 age and gender matched nonsingers.

METHODS

From each participant, measures of highest phonational frequency, lowest intensity, jitter, and maximum phonation time were obtained. Using these, DSI values were calculated.

RESULTS

Singers had significantly greater highest phonational frequency, longer maximum phonation time, and higher DSI values. When compared with the younger participants, older participants had significantly reduced highest phonational frequency, maximum phonation time, and DSI values.

CONCLUSIONS

The results of this study suggest that DSI values vary between Carnatic classical singers and nonsingers, and hence separate normative data may need to be established for this group of singers for clinical comparison purposes.

Laryngeal and respiratory behavior during pitch change in professional singers

The aim of this study was to examine the physiology of pitch change in terms of laryngeal and respiratory mechanisms in professional singers. Nine female professional singers were recruited to participate in the study. Videoendoscopic recordings of the participants producing one-octave ascending and descending scales were used as a basis to apply a ratio measurement of vocal fold length for each note produced on the scale. Simultaneous respiratory data using Respitrace were also collected. Questionnaires (Voice Handicap Index and Vocal Questionnaire) were used to obtain information about psychosocial aspects related to voice use. Two vocal fold lengthening patterns (static and dynamic) were observed with pitch change. Participants exhibiting a static pattern of vocal fold lengthening had fewer years of vocal training, exhibited a more variable use of vital capacity, and also began the singing task at a higher position in their vital capacity. The reverse was true for participants exhibiting a dynamic vocal fold pattern. These preliminary data indicate that the pattern of vocal fold lengthening exhibited by singers may be related to the number of years of training possessed. Furthermore, the data indicate that stability in one subsystem may result in variability in another, as shown by the interaction between the vocal fold and respiratory patterns.

Development of an Auditory-Perceptual Rating Instrument for the Operatic Singing Voice

Although considerable progress has been made in the development of acoustic and physiological measures of operatic singing voice, there is still no widely accepted objective tool for the evaluation of its multidimensional features. Auditory-perceptual evaluation, therefore, remains an important evaluation method for singing pedagogues, voice scientists, and clinicians who work with opera singers. Few investigators, however, have attempted to develop standard auditory-perceptual tools for evaluation of the operatic voice. This study aimed to pilot test a new auditory-perceptual rating instrument for operatic singing voice. Nine expert teachers of operatic singing used the instrument to rate the singing voices of 21 professional opera chorus artists from a national opera company. The findings showed that the instrument has good face validity, that it can be legitimately treated as a psychometrically sound scale, and that raters can use the scale consistently, both between and within judges. This new instrument, therefore, has the potential to allow opera singers, their teachers, voice care clinicians, and researchers to evaluate the important auditory-perceptual features of operatic voice quality.

Influence of glottal closure configuration on vocal efficacy in young normal-speaking women

Posterior closure insufficiency of the glottis is often mentioned in connection with permanent voice disorders. Recently published studies have revealed that an incomplete closure of the glottis can be found also in normal-speaking voices, especially in women. However, the effect of glottal closure configuration on vocal efficacy is not sufficiently clarified. The purpose of this study was to determine the effect of glottal closure configuration on singing and speaking voice characteristics. Overall, 520 young female normal-speaking subjects were examined by videostroboscopy for different phonation conditions in the combination of soft, loud, low, and/or high phonation and by voice range profile measurements. According to the videostroboscopic analysis, the subjects were subdivided into four groups: complete closure of the vocal folds already in soft phonation (group 1), closure of the vocal fold with increasing intensity (group 2), persistent closure insufficiencies despite increasing intensity (group 3), and hourglass-shaped closure in subjects with vocal nodules (group 4). Subjects in which the glottal closure could not be evaluated sufficiently were subclassified into group 5 (missing values). Selected criteria of the singing and speaking voice were evaluated and statistically processed according to the mentioned subclassification. Group 1 reached significantly the highest sound pressure levels (SPLmax) for the singing voice as well as for the shouting voice. Group 3 showed a limited capacity to increase the intensity of the singing and speaking voice. The results gathered in this study objectify the relationship of insufficient glottal closure and reduced vocal capabilities. As long as no conclusive data on long-term consequences of insufficient glottal closure are available, a prophylactic improvement of the laryngeal situation especially in female professional voice users by voice therapy should be recommended.

Instrumental and perceptual evaluations of two related singers

The primary goal of this study was to characterize a performer's singing and speaking voice. One woman was not admitted to a premier choral group, but her sister, who was comparable in physical characteristics and background, was admitted and provided a valuable control subject. The perceptual judgment of a vocal coach who conducted the group's auditions was decisive in discriminating these 2 singers. The singer not admitted to the group described a history of voice pathology, lacked a functional head register, and spoke with a voice characterized by hoarseness. Multiple listener judgments and acoustic and aerodynamic evaluations of both singers provided a more systematic basis for determining: 1) the phonatory basis for this judgment; 2) whether similar judgments would be made by groups of vocal coaches and speech-language pathologists; and 3) whether the type of tasks (e.g., sung vs. spoken) would influence these judgments. Statistically significant differences were observed between the ratings of vocal health provided by two different groups of listeners. Significant interactions were also observed as a function of the types of voice samples heard by these listeners. Instrumental analyses provided evidence that, in comparison to her sister, the rejected singer had a compromised vocal range, glottal insufficiencies as assessed aerodynamically and electroglottographically, and impaired acoustic quality, especially in her speaking voice.

Relationship between aerodynamic measures of glottal efficiency and stroboscopic findings in asymptomatic singing students

Singing requires exquisite coordination between the respiratory and phonatory systems to efficiently control glottal airflow. Asymptomatic singing students underwent pulmonary function testing (PFT), videostrobolaryngoscopic examination, and measures of glottal efficiency (maximum phonation time [MPT], glottal flow rate [GFR], and phonation quotient [PQ]) performed in both a sung and spoken tone. Pulmonary function and glottal efficiency values were within reported normative data for professional singers. However, sung tones were made with significantly higher GFR and PQ and lower PQ than spoken tones. The mean GFR was not related to the degree of glottal closure (by videostrobolaryngoscopy) or underlying pulmonary support.