REVIEW URRENT C OPINION
Managing dysphonia in occupational voice users Mara Behlau a,b, Fabiana Zambon a,b,c, and Glaucya Madazio a
Purpose of review Recent advances with regard to occupational voice disorders are highlighted with emphasis on issues warranting consideration when assessing, training, and treating professional voice users. Recent findings Findings include the many particularities between the various categories of professional voice users, the concept that the environment plays a major role in occupational voice disorders, and that biopsychosocial influences should be analyzed on an individual basis. Assessment via self-evaluation protocols to quantify the impact of these disorders is mandatory as a component of an evaluation and to document treatment outcomes. Discomfort or odynophonia has evolved as a critical symptom in this population. Clinical trials are limited and the complexity of the environment may be a limitation in experiment design. Summary This review reinforced the need for large population studies of professional voice users; new data highlighted important factors specific to each group of voice users. Interventions directed at student teachers are necessities to not only improving the quality of future professionals, but also to avoid the frustration and limitations associated with chronic voice problems. The causative relationship between the work environment and voice disorders has not yet been established. Randomized controlled trials are lacking and must be a focus to enhance treatment paradigms for this population. Keywords call center agents, dysphonia, occupational voice disorders, professional voice, quality of life, soldiers, teachers, voice, voice symptoms
INTRODUCTION Vocal performance is an ancient art and professional voice users were likely the first patients to seek care for voice problems related to chronic misuse of the vocal mechanism. However, only recently, the seminal work of Vilkman (2000) [1] considered vocal quality and vocal load in this population, providing a conceptual framework for the field and a change in how these challenging patients are considered. Vocal quality depends on both the artistic and nonartistic nature of voice usage. Even when focusing only on the artistic component, requirements may vary enormously, for example, from the pure sound required for classical singing to a distorted quality for heavy metal performers. To the contrary, vocal load is derived from a combination of the duration of voice usage and environmental factors (room acoustics, air quality, and type of communication). Physical load on the vocal apparatus may require physiological changes increasing the occupational risk. Moreover, environmental factors may affect vocal load in a complex manner [2]. A new taxonomy system was recently proposed [3] to categorize professional voice users according www.co-otolaryngology.com
to the nature of their vocal demands (i.e., the prime motivation for voice use): supporters, callers, transmitters, informers, leader and sellers, and performers. This system may be helpful, with implications for managing voice problems in specific situations. However, it has not gained popularity to date. In spite of these advances, a multicentric approach is necessary to address some of the basic issues including obtaining epidemiological data as well as the characterization of certain occupations, and eventually, the development of clinical trials to test various interventions.
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Centro de Estudos da Voz – CEV, bUniversidade Federal de Sa˜o Paulo – UNIFESP and cSindicato dos Professores de Sa˜o Paulo – SINPRO, Sa˜o Paulo, Brazil Correspondence to Mara Behlau, PhD, Centro de Estudos da Voz, Rua Machado Bittencourt 361, Sa˜o Paulo, SP 04044-001, Brazil. E-mail: [email protected] Curr Opin Otolaryngol Head Neck Surg 2014, 22:188–194 DOI:10.1097/MOO.0000000000000047 Volume 22 Number 3 June 2014
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Managing dysphonia in occupational voice users Behlau et al.
maintain their attention to impart knowledge. Each discipline demands peak performance to ensure longevity. Clinicians often have a narrow perception of each of these specific aspects. Only recently, the scientific literature has begun to address preferences for certain voices with each industry, such as the radio performers [12 ] or call center operators [13,14]. A recent qualitative Australian study [12 ] included nine semi-structured interviews with radio employers and concluded that these professionals sound differently than in the past. The tendency is to use a natural sound, easy-on-the-ear, with the ability to read and produce vocal quality that suits the station. In spite of the perception of the vocal demands, the interviewees did not express any concern regarding vocal health. To this end, employers and clinicians must exchange information. A lack of training cannot be repeatedly discussed as the main cause for voice complaints; environmental factors related to voice disorders must be addressed.
KEY POINTS Occupational and professional voice users are considered traditional patients with regard to voice disorders, but there is no consensus regarding the definition of an occupational voice disorder.
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Many specific professional demands may contribute to both transient and chronic vocal problems and the environment must be taken into consideration in the assessment and management of this population.
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Epidemiological studies are limited and variable in quality; caution should be taken when attributing a voice disorder to an occupation. Professional voice users do not always recognize perceptual auditory symptoms and signs of discomfort as important factors warranting consultation, which can delay treatment.
OCCUPATIONAL VOICE DISORDERS VERSUS PROFESSIONAL VOICE DISORDERS
EPIDEMIOLOGY
It is estimated that one-third of the world‘s current workforce consists of individuals who rely on voice as a primary tool of work [4]. Occupational disorders are seen as diseases caused by exposure at work [2,5], primarily related to the occupation itself. Nevertheless, no consensus exists regarding the definition of occupational voice disorders [6]. The terms professional and occupational voice have been used interchangeably, but recent publications tend to employ the term occupational voice when dealing with safety and health in the workplace [7 ,8 ] and professional voice when referring to specific personal conditions [9,10]. As with any voice problem, dysphonia in professional users is multifactorial with the added complexity of an environment that is likely difficult to manipulate. Although there is no international position statement, in some countries such as Poland, a combination of medical and legal aspects defines voice disorders as an occupational disease [11]. Voice disorders occur when an individual‘s voice fails to meet the criteria and demands necessitated by the profession [1]. Professional voice users work in a wide range of disciplines and genres. The classical singer demands a specific vocal quality for subsistence, the actor relies on vocal flexibility to embody a character, the clergy on endurance and expressivity, the radio performer‘s voice must correspond to a specific market, and the teacher needs not only a resilient voice, but also a unique communicative competence to attract students and
Incidence data regarding voice disorders in professional voice users depend highly on methodology, variables, and types of samples investigated. Quantification of voice disorders in the workplace may be difficult, as a causal relationship is often difficult to prove. Some interesting data reinforce the notion that teachers present with significant limitations regardless of the cultural scene [15]. Recently, a comprehensive investigation in Brazil studied 3265 people [16 ]. The results were strikingly similar to data obtained in the United States by Roy et al. [17,18], a randomized study. Voice symptoms were highly related to occupational use; the lifetime prevalence was 63% for teachers (35% for nonteachers). This figure increased at 30–39 years and persisted with advancing age. Teachers presented with an average of 3.6 symptoms (2.3 in the general population), including vocal fatigue, increased effort to talk, and discomfort. Teachers missed more workdays during the year (12 vs. 2.4% at the general population) because of diminished capacity to perform certain tasks (29 vs. 5.4% general population). Some actually considered a change in career due to voice problems (16.7 vs. 0.9% general population). A cross-sectional epidemiological study [19] of Brazilian teachers (N ¼ 4496) revealed a mix of individual and environmental factors contributing to voice disorders: vocal effort was associated with dysphonia in addition to female sex, lack of amplification, increased background noise, administrative pressures, heartburn, and rhinitis. Similar
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figures were also found in North Carolina, United States, in 237 kindergarten teachers: 58% presented with lifetime hoarseness and 22% were currently hoarse. Moreover, although 32% sought professional help, 30% believed that hoarseness was normal [20]. Several work-related and individual variables were associated with voice disorders worldwide such as noise in classrooms, being a physical education instructor, and habitual loud speaking voice [15]. An interesting Brazilian study of 575 teachers from urban and rural public schools [21] concluded that there is a close association between voice problems and common mental disorders (mood, anxiety, or somatoform disorders). Elevated scores on the emotional domain of the Voice Handicap Index (VHI) were related to large class size, lack of voice rest, and loss of workdays due to voice problems. Similarly, elevated scores on the functional subscale were related to female sex, lack of voice rest, loss of working days due to voice problems, and increased vocal load. Student teachers were assessed in Sweden and a high prevalence of voice disorders (17%) was observed, suggesting the need for early intervention [22]. From a large group of 1250 students, 208 presented with at least two symptoms weekly. Risk factors included female sex, vocal fold problems in childhood and/or adulthood, throat infections, airborne allergies, smoking, hearing problems, previous work as teacher or leader, vocally taxing hobbies, and previous voice therapy or voice training. A strong association was observed between the number of potential risk factors and voice symptoms. Risk factors were not related to the work environment because these students had not yet been exposed to teaching. In addition to teachers, recent studies have focused on soldiers, cantors, professional soccer managers, and fitness instructors. Dion et al. [8 ] analyzed 1.3 million health records of active duty US army soldiers with no history of dysphonia. Soldiers have occupational and environmental exposure, reduced hydration, hot dry climates, altered sleep patterns, and many other stressors. Voice is a key element in combat situations and a voice disorder may be dangerous. Soldiers were 1.13 times more likely to have dysphonia if they were deployed. A lack of association with diagnosis type, tobacco, and alcohol use indicates specific occupational exposures, warranting the implementation of preventive measures. Cantors [23] maintain a vocally intense lifestyle and have been largely underserved with regard to voice problems. These professionals face the challenge of both singing and teaching and present with &
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risk factors for developing dysphonia, including high vocal demands, reduced vocal downtime, allergies, and reflux. O’Neill and McMenamin [24] described voice use among professional soccer managers in Ireland and identified four variables related to increased risk for dysphonia: voice use, factors affecting voice change, impact of voice use, and the importance of voice at work. These risk factors were related to intense and prolonged voice use in poor acoustic environments and lack of vocal technique. Finally, Rumbach [25] reported on 38 Australian fitness instructors that revealed a lack of job satisfaction (65%) and emotional distress. The need to be more proactive is clear; however, critical epidemiological data are lacking.
COMMON PRESENTING SIGNS, SYMPTOMS, AND LARYNGEAL FINDINGS Vocal endurance seems to be more critical than vocal quality for many professionals. Flexibility can also be a particular requirement for some individuals such as the impersonators [9]; this variable has not been studied adequately. Symptoms in professional voice users do not always reflect awareness of a vocal problem and do not usually relate to decreased professional performance [7 ,13,26,27]. Symptomatology can be abundant [16 ,18,22] with no specific sign or symptom to clearly represent the main complaint of a professional voice user. Nevertheless, these individuals clearly link voice and/or discomfort with the workplace [16 ,18,28–30]. Discomfort with phonation is a key issue in teachers and may be the predominant symptom among these professionals [28,29]. The Voice Discomfort Scale [31] was employed to study teachers and revealed that discomfort was associated with diminished vocal self-assessment, but did not necessarily correlate with the degree of dysphonia [28]. Therapy can reduce the frequency and severity of discomfort symptoms quantified by this scale [29]. Pain during speaking in professional and nonprofessional voice users was studied in a large sample of 1152 Belgian individuals [32]. Significantly more pain symptoms were observed in professional voice users (84 vs. 55%). These symptoms were isolated to the throat, neck, shoulder, headache, ear, and back pain. Vocal training may play a role in reducing pain [33]. Recognition of the increased number of symptoms in the professional voice population is critical; however, as voice problems are typically chronic, increased symptoms do not lead to treatment seeking. The average number of symptoms necessary to motivate teachers to seek diagnosis and treatment &&
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was 8.6 [27]. Beyond the number and frequency of symptoms, recovery time following heavy vocal load appears to play a role in the perception of vocal dysfunction [34]. Interestingly, when student teachers were assessed [22], symptoms of discomfort during phonation were most common. Specific laryngeal information on student teachers reinforced the need for early intervention. Data from 30 first-year American acting students [26] revealed incomplete glottal closure (62%), hyperfunction (59%), decreased mucosal wave (55%), and findings of laryngopharyngeal reflux (48%). Similarly alarming data were reported for 79 first-year Israeli acting students [35], with 50% prevalence of aberrant laryngeal findings, and associated with auditory and acoustic deviations. Even if these findings are not life-threatening, they may cause stress, impair work conditions, and limit career longevity. An Australian fitness instructors group [30] presented with laryngeal disorder, even if working with amplification (80%), including vocal fold nodules (80%; N ¼ 30), cysts (6.6%), hemorrhage (3.33%), and recurrent chronic laryngitis (10%) in addition to vocal strain and muscle tension dysphonia. These professionals self-reported acute (78.95%) and chronic (70.91%) voice symptoms [25] as well as a negative impact of their voice on their lives, including social withdrawal, decreased job satisfaction, and emotional distress. Clearly, amplification does not ameliorate these issues. The Screening Index for Voice Disorder (SIVD) was proposed as an instrument of epidemiologic screening tool for teachers with voice problems [36]. It is not clear, however, how specific this instrument is with regard to teachers when compared with the general population or other professional categories. A critical lack of data regarding professional populations without voice problems remains problematic. A study of 72 American trained singers with no voice complaints [37] revealed a high occurrence of abnormalities on strobovideolaryngoscopy (86.1% of participants: laryngopharyngeal reflux, prominent varicosities or ectasias, incomplete glottic closure, and/or structural abnormalities) and acoustic analysis (deviated values from the norm in shimmer, relative average perturbation, and maximum fundamental frequency for female participants). These data must be considered when assessing a singer. Many predisposing factors in professional voice users have been described, such as lack of training, health-related problems, and psychological stressors [2,38,39]; however, none of these explain why certain people present with dysphonia, whereas others, under the same conditions, are more resilient.
Vocal behavior is usually considered an important risk factor; however, a recent Italian study of 92 callcenter operators using the ambulatory phonation monitor during a workday concluded that neither the number of working hours nor the percentage of phonation time was statistically related to the perception of voice disturbances [40 ]. A recent review regarding functional voice problems [41] proposed a cognitive behavioral model to deal with these patients. Individual factors (genetics, early experience, and personality), precipitating factors (life events and coping, vocal vulnerability), and perpetuating factors (anxiety, depression, and general fatigue) were proposed to be causative in voice problems. Even if this review did not focus specifically on professional voice users, it was clear that vocal vulnerability was the consequence of vocal load, which fits the current model of occupational voice demands. &
ASSESSMENT CRITERIA AND ASSESSMENT MEASURES Patients with voice problems are typically assessed by a multidisciplinary team consisting of an otolaryngologist and a speech-language pathologist. A singing specialist, voice coach, and/or psychologist may also be required. The European Laryngological Society proposed a standard assessment protocol for evaluating voice problems: perception, videostroboscopy, acoustics, aerodynamics, and subjective rating by the patient [42]. According to the American Academy of Otolaryngology–Head and Neck Surgery, the minimum battery to evaluate a patient with vocal complaint is clinical history, physical examination, and visualization of the larynx via laryngoscopy [43]. Specific procedures for screening, assessment, or follow-up of professional voice users have not been proposed. For the speech-language pathologist evaluation, auditory and acoustic analyses are fundamental to understand the underlying physiology. Moreover, the inclusion of self-assessment protocols to evaluate the impact of a voice problem is mandatory to help understand the relationship between the patient and his or her problem, to estimate adherence and coping, and to establish a prognosis [27,44]. Auditory analysis may not be reliable; a distorted voice may be characteristic of an actor, for example. Perception of the voice may not reflect discomfort during phonation; auditory assessment may underestimate the problem. Even if there is some evidence for selected acoustic, laryngeal imaging, auditory perceptual, functional, and aerodynamic measures to be used as effective components in a clinical voice evaluation [44],
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high-level research to provide evidence regarding these recommendations is warranted. Normative data for professional voice users and for aging professionals are also required [37]. Recently, an Italian group [45] proposed the use of the singing power ratio as an electroacoustic measure, correlated to both the years of singing activity and the vocal category of each singer. Moreover, it was highly correlated to clinician subjective assessment. Professional choir singers usually have a long career; to understand the difference between normal aging problems and the effect of the professional voice remains challenging [10]. Professional voice users may manipulate their voice to reduce the negative impact of a voice problem, which may pose difficulties in the evaluative process. The use of specific protocols for self-assessment of the singing voice was proposed [46–49] as a more sensitive tool, but data are limited. No specific protocols for professional speaking voice were proposed. In London, students of the arts seem to be at increased risk for voice problems as quantified by the VHI-10 [50]. Additionally, high scores were found in musical theater students (n ¼ 49) when compared with medical students (n ¼ 43), particularly in three specific domains: voice strain, lack of clarity, and being upset from voice problem [50]. It is difficult to interpret these findings as they may reflect awareness of a potential voice problem or initial symptoms due to a greater voice use over time. Regardless, the need for early laryngeal examination and voice evaluation of future professional voice users is enhanced by these findings. Even when employing a specific protocol, the S-VHI [51], musical theater singers perceived subtle fluctuations or changes in physical functioning of the voice that were not detected by the instrument. These symptoms became clear through a series of focus group interviews (n ¼ 43) and a written survey (n ¼ 36) to detail the perception of the impact of performing after a show, across a working week, and across a production season. A list of 97 descriptors was generated using the singers’ own terminology and experiences: symptoms of vocal impairment, vocal fatigue, and descriptors of positive vocal changes as a consequence of heavy vocal load. From this list, the 20-item Evaluation of the Ability of Singing Ease was created to assess the perceptions of healthy singers with regard to the singing voice as a function of vocal load [52 ]. This scale has potential to be included in clinical and performance settings. Behavioral evaluation of the professional voice usage in situ may offer important data nonreadily ascertained during the clinical consultation [40 ]; however, this protocol is likely often impractical. &
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Effectiveness of voice training and treatment programs Voice training focuses on vocal health, can potentially prevent voice problems, and is usually employed for improving normal voices for a specific demand, whereas treatment aims at correcting functional deficits. Training and therapy may use direct approaches (vocal exercises) and/or indirect strategies (relaxation, breathing techniques, and vocal hygiene information). Vocal hygiene is a component of almost all programs and some suggestions are common sense and have been used for more than one century [53]. Voice rest is an empiric treatment, but it is a challenge to select cases that can really benefit from complete silence. The concept of compounded and noncompounded phonotrauma may be used as a guide to predict success or failure of voice rest regimens; in complex phonotraumatic dysphonia, voice rest may be analogous to crash diets in the morbidly obese. However, in noncompounded cases, vocal rest may be a viable option [54]. Intervention studies are rare likely related to methodological complexity, which is even higher for professional voice users. Teachers and telemarketers have been the focus of the sparse literature to date. Osteopathic therapy, myofascial techniques together with voice exercises, relaxation, and aerobic activities apart from balneological treatment were used to treat 40 teachers with chronic vocal problems, in a health spa in Poland [55]. A reduction of tenderness and normalization of perilaryngeal tonus was observed. In spite of these favorable outcomes, the concept of a voice spa is difficult to implement elsewhere. The program proposed is too broad and the lack of a control group is problematic. Another study of 40 American female kindergarten and primary school teachers showed that the use of an individual, portable vocal amplification system reduced vocal fatigue and the degree of vocal deviation. Vocal dosage and intensity was also reduced with the use of a portable voice amplifier [56]. Participants maintained the reduced vocal intensity level after returning the amplification device. The telemarketing industry has become increasingly critical since the 1970s and it is one of the fastest growing businesses worldwide [7 ]. A representative effort in the UK proposed qualitative and quantitative research protocols applied to telemarketers and managers of 13 call centers [57]; poor vocal health habits and the lack of vocal training were common findings in this population and symptoms of reported muscle tension and voice problems had a marked impact on work. Specific training for all workers was recommended, particularly for those early in their career. A recent survey in India [14] &&
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analyzed 1093 call center workers from 11 centers. Data suggest the current prevalence of dysphonia was 59 and 27%, respectively, with female workers missing more days of work. The effectiveness of a voice training program was analyzed by comparing 14 Brazilian call center agents who underwent an 8-week training and 34 controls [58]. Unfortunately, the high rate of participant dropout in both groups was problematic. Perceptual analysis did not show improvement; however, jitter was consistently reduced after training, which can be considered an indirect measure of voice stability. More sensitive measures must be selected to better reflect improvement in professional voice users. In addition to training, real-time biofeedback seems highly promising. A prevention study was performed in Austria [7 ] with 76 call center operators. The study group used realtime biofeedback software (VidiVoice) for 4 weeks to improve vocal self-assessment and performance by monitoring fundamental frequency, intensity, and syllables per minute. Participants with vocal fatigue showed a larger voice range profile; moreover, all participants with hypofunction improved. This work tested the software in real-life situations, providing participants with the opportunity to optimize vocal performance at work. The effect of a 6-h voice training program (direct and indirect approaches) and a 30-min individual counseling session was investigated in 51 Belgian student teachers and 30 controls [59]. Several objective parameters improved in the training group, most significantly in female participants. The results support the effectiveness of this program and favor its introduction in the education of student teachers due to the already high prevalence of problems in this yet nonworking population [22,26,35]. Teachers usually consider their dysphonia as a part of their occupation [16 ] and a good strategy to improve adherence for these chronically dysphonic patients seems to be to offer the experience of an immediate change in vocal quality and/or discomfort with a simple exercise protocol [60]. It is complex to define an ideal voice for a professional user, particularly when considering the singing voice. A distorted ‘harsh’ voice can be quite valuable for a pop artist or heavy metal vocalist. However, this style can lead to a devastating voice disorder. Vocal rehabilitation for artists with intentional distortions should aim at a resilient and effective voice regardless of the sound [61]. It is possible to produce a healthy distorted sound for a specific market purpose, but no studies have focused on this issue. The cost-benefit ratio of providing therapy remains unclear and warrants further investigation. &&
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CONCLUSION The area of professional voice has grown with regard to our understanding of the specifics of the professional voice user. However, the main focus remains on teachers. Large population studies are needed and interventions targeting student teachers must be implemented to avoid frustration and chronic voice problems. However, a causative relationship between the workplace and voice disorders has yet to be established. Furthermore, longitudinal studies and randomized controlled trials are needed. Acknowledgements None. Conflicts of interest The authors declare no conflicts of interest.
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41. Deary V, Miller T. Reconsidering the role of psychosocial factors in functional dysphonia. Curr Opin Otolaryngol Head Neck Surg 2011; 19:150– 154. 42. Dejonckere PH, Bradley P, Clemente P, et al. A basic protocol for functional assessment of voice pathology, especially for investigating the efficacy of (phonosurgical) treatments and evaluating new assessment techniques. Guideline elaborated by the Committee on Phoniatrics of the European Laryngological Society (ELS). Eur Arch Otorhinolaryngol 2001; 258:77– 82. 43. Schwartz SR, Cohen SM, Dailey SH, et al. Clinical practice guideline: hoarseness (dysphonia). Otolaryngol Head Neck Surg 2009; 141:S1– S31. 44. Roy N, Barkmeier-Kraemer J, Eadie T, et al. Evidence-based clinical voice assessment: a systematic review. Am J Speech Lang Pathol 2013; 22:212– 226. 45. Cesari U, Iengo M, Apisa P. Qualitative and quantitative measurement of the singing voice. Folia Phoniatr Logop 2012; 64:304–309. 46. Cohen SM, Jacobson BH, Garrett CG, et al. Creation and validation of the Singing Voice Handicap Index. Ann Otol Rhinol Laryngol 2007; 116:402– 406. 47. Morsomme D, Gaspar M, Jamart J, et al. Adaptation du Voice Handicap Index a` la voixchante´e [Adaptation of Voice Handicap Index to singing voice]. Rev Laryngol Otol Rhinol 2007; 128:305–314. 48. Fussi F, Fuschini T. Foniatria artistica: la presa in carico foniatricologopedicadel cantante classico e moderno [Artistic phoniatric: the role of the physician and speech language pathology in classic and modern singing]. Audiol Foniatr 2008; 13:4–28. 49. Murry T, Zschommler A, Prokop J. Voice handicap in singers. J Voice 2009; 23:376–379. 50. Watson NA, Oakeshott P, Kwame I, Rubin JS. A comparison of the Voice Handicap Index-10 scores between medical and musical theater students. J Voice 2013; 27:129; e21-129. e23. 51. Phyland DJ, Thibeault SL, Benninger MS, et al. Perspectives on the impact on vocal function of heavy vocal load among working professional music theater performers. J Voice 2013; 27:390; e31-9. 52. Phyland DJ, Pallant JF, Benninger MS, et al. Development and preliminary & validation of the EASE: a tool to measure perceived singing voice function. J Voice 2013; 27:454–462. This is an interesting protocol, with 20 items and two subscales (physical symptoms of vocal fatigue and mucosal changes) carefully developed to assess the singer‘s perception of the current status of their singing voices. 53. Ruben RJ. Morell Mackenzie’s The hygiene of the vocal organs: a study in longevity or durability. Laryngoscope 2014; 124:522–530. 54. Haben CM. Voice rest and phonotrauma in singers. Med Probl Perform Art 2012; 27:165–168. 55. Marszałek S, Niebudek-Bogusz E, Woz´nicka E, et al. Assessment of the influence of osteopathic myofascial techniques on normalization of the vocal tract functions in patients with occupational dysphonia. Intern J Occup Med Environ Health 2012; 25:225–235. 56. Gaskill SC, O’Brien SG, Tinter SR. The effect of voice amplification on occupational vocal dose in elementary school teachers. J Voice 2012; 26:667; e19-27. 57. Hazlett DE, Duffy OM, Moorhead SA. Review of the impact of voice training on the vocal quality of professional voice users: implications for vocal health and recommendation for further research. J Voice 2011; 25:181–191. 58. Oliveira AG, Gouveia N, Behlau M. The effectiveness of a voice training program for telemarketers. J Voice 2012; 26:815; e1-8. 59. Timmermans B, Coveliers Y, Wuyts FL, Looy LV. Voice training in teacher education: the effect of adding an individualized microteaching session of 30 minutes to the regular 6-hour voice training program. J Voice 2012; 26:669; e1-9. 60. Paes SM, Zambon F, Yamasaki R, et al. Immediate effects of the Finnish resonance tube method on behavioral dysphonia. J Voice 2013; 22:717– 722. 61. Wendler J, Dejonckere PH, Wienhausen S, et al. Therapeutic consequences from changing voice ideals (clear to harsh, pleasant to jarring): summarizing report on a round-table discussion at the 5th world voice congress, Luxor, Egypt, 27-31 October 2012. Logoped Phoniatr Vocol 2013. [Epub ahead of print]
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Managing dysphonia in occupational voice users Mara Behlau a,b, Fabiana Zambon a,b,c, and Glaucya Madazio a
Purpose of review Recent advances with regard to occupational voice disorders are highlighted with emphasis on issues warranting consideration when assessing, training, and treating professional voice users. Recent findings Findings include the many particularities between the various categories of professional voice users, the concept that the environment plays a major role in occupational voice disorders, and that biopsychosocial influences should be analyzed on an individual basis. Assessment via self-evaluation protocols to quantify the impact of these disorders is mandatory as a component of an evaluation and to document treatment outcomes. Discomfort or odynophonia has evolved as a critical symptom in this population. Clinical trials are limited and the complexity of the environment may be a limitation in experiment design. Summary This review reinforced the need for large population studies of professional voice users; new data highlighted important factors specific to each group of voice users. Interventions directed at student teachers are necessities to not only improving the quality of future professionals, but also to avoid the frustration and limitations associated with chronic voice problems. The causative relationship between the work environment and voice disorders has not yet been established. Randomized controlled trials are lacking and must be a focus to enhance treatment paradigms for this population. Keywords call center agents, dysphonia, occupational voice disorders, professional voice, quality of life, soldiers, teachers, voice, voice symptoms
INTRODUCTION Vocal performance is an ancient art and professional voice users were likely the first patients to seek care for voice problems related to chronic misuse of the vocal mechanism. However, only recently, the seminal work of Vilkman (2000) [1] considered vocal quality and vocal load in this population, providing a conceptual framework for the field and a change in how these challenging patients are considered. Vocal quality depends on both the artistic and nonartistic nature of voice usage. Even when focusing only on the artistic component, requirements may vary enormously, for example, from the pure sound required for classical singing to a distorted quality for heavy metal performers. To the contrary, vocal load is derived from a combination of the duration of voice usage and environmental factors (room acoustics, air quality, and type of communication). Physical load on the vocal apparatus may require physiological changes increasing the occupational risk. Moreover, environmental factors may affect vocal load in a complex manner [2]. A new taxonomy system was recently proposed [3] to categorize professional voice users according www.co-otolaryngology.com
to the nature of their vocal demands (i.e., the prime motivation for voice use): supporters, callers, transmitters, informers, leader and sellers, and performers. This system may be helpful, with implications for managing voice problems in specific situations. However, it has not gained popularity to date. In spite of these advances, a multicentric approach is necessary to address some of the basic issues including obtaining epidemiological data as well as the characterization of certain occupations, and eventually, the development of clinical trials to test various interventions.
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Centro de Estudos da Voz – CEV, bUniversidade Federal de Sa˜o Paulo – UNIFESP and cSindicato dos Professores de Sa˜o Paulo – SINPRO, Sa˜o Paulo, Brazil Correspondence to Mara Behlau, PhD, Centro de Estudos da Voz, Rua Machado Bittencourt 361, Sa˜o Paulo, SP 04044-001, Brazil. E-mail: [email protected] Curr Opin Otolaryngol Head Neck Surg 2014, 22:188–194 DOI:10.1097/MOO.0000000000000047 Volume 22 Number 3 June 2014
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Managing dysphonia in occupational voice users Behlau et al.
maintain their attention to impart knowledge. Each discipline demands peak performance to ensure longevity. Clinicians often have a narrow perception of each of these specific aspects. Only recently, the scientific literature has begun to address preferences for certain voices with each industry, such as the radio performers [12 ] or call center operators [13,14]. A recent qualitative Australian study [12 ] included nine semi-structured interviews with radio employers and concluded that these professionals sound differently than in the past. The tendency is to use a natural sound, easy-on-the-ear, with the ability to read and produce vocal quality that suits the station. In spite of the perception of the vocal demands, the interviewees did not express any concern regarding vocal health. To this end, employers and clinicians must exchange information. A lack of training cannot be repeatedly discussed as the main cause for voice complaints; environmental factors related to voice disorders must be addressed.
KEY POINTS Occupational and professional voice users are considered traditional patients with regard to voice disorders, but there is no consensus regarding the definition of an occupational voice disorder.
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Many specific professional demands may contribute to both transient and chronic vocal problems and the environment must be taken into consideration in the assessment and management of this population.
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Epidemiological studies are limited and variable in quality; caution should be taken when attributing a voice disorder to an occupation. Professional voice users do not always recognize perceptual auditory symptoms and signs of discomfort as important factors warranting consultation, which can delay treatment.
OCCUPATIONAL VOICE DISORDERS VERSUS PROFESSIONAL VOICE DISORDERS
EPIDEMIOLOGY
It is estimated that one-third of the world‘s current workforce consists of individuals who rely on voice as a primary tool of work [4]. Occupational disorders are seen as diseases caused by exposure at work [2,5], primarily related to the occupation itself. Nevertheless, no consensus exists regarding the definition of occupational voice disorders [6]. The terms professional and occupational voice have been used interchangeably, but recent publications tend to employ the term occupational voice when dealing with safety and health in the workplace [7 ,8 ] and professional voice when referring to specific personal conditions [9,10]. As with any voice problem, dysphonia in professional users is multifactorial with the added complexity of an environment that is likely difficult to manipulate. Although there is no international position statement, in some countries such as Poland, a combination of medical and legal aspects defines voice disorders as an occupational disease [11]. Voice disorders occur when an individual‘s voice fails to meet the criteria and demands necessitated by the profession [1]. Professional voice users work in a wide range of disciplines and genres. The classical singer demands a specific vocal quality for subsistence, the actor relies on vocal flexibility to embody a character, the clergy on endurance and expressivity, the radio performer‘s voice must correspond to a specific market, and the teacher needs not only a resilient voice, but also a unique communicative competence to attract students and
Incidence data regarding voice disorders in professional voice users depend highly on methodology, variables, and types of samples investigated. Quantification of voice disorders in the workplace may be difficult, as a causal relationship is often difficult to prove. Some interesting data reinforce the notion that teachers present with significant limitations regardless of the cultural scene [15]. Recently, a comprehensive investigation in Brazil studied 3265 people [16 ]. The results were strikingly similar to data obtained in the United States by Roy et al. [17,18], a randomized study. Voice symptoms were highly related to occupational use; the lifetime prevalence was 63% for teachers (35% for nonteachers). This figure increased at 30–39 years and persisted with advancing age. Teachers presented with an average of 3.6 symptoms (2.3 in the general population), including vocal fatigue, increased effort to talk, and discomfort. Teachers missed more workdays during the year (12 vs. 2.4% at the general population) because of diminished capacity to perform certain tasks (29 vs. 5.4% general population). Some actually considered a change in career due to voice problems (16.7 vs. 0.9% general population). A cross-sectional epidemiological study [19] of Brazilian teachers (N ¼ 4496) revealed a mix of individual and environmental factors contributing to voice disorders: vocal effort was associated with dysphonia in addition to female sex, lack of amplification, increased background noise, administrative pressures, heartburn, and rhinitis. Similar
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figures were also found in North Carolina, United States, in 237 kindergarten teachers: 58% presented with lifetime hoarseness and 22% were currently hoarse. Moreover, although 32% sought professional help, 30% believed that hoarseness was normal [20]. Several work-related and individual variables were associated with voice disorders worldwide such as noise in classrooms, being a physical education instructor, and habitual loud speaking voice [15]. An interesting Brazilian study of 575 teachers from urban and rural public schools [21] concluded that there is a close association between voice problems and common mental disorders (mood, anxiety, or somatoform disorders). Elevated scores on the emotional domain of the Voice Handicap Index (VHI) were related to large class size, lack of voice rest, and loss of workdays due to voice problems. Similarly, elevated scores on the functional subscale were related to female sex, lack of voice rest, loss of working days due to voice problems, and increased vocal load. Student teachers were assessed in Sweden and a high prevalence of voice disorders (17%) was observed, suggesting the need for early intervention [22]. From a large group of 1250 students, 208 presented with at least two symptoms weekly. Risk factors included female sex, vocal fold problems in childhood and/or adulthood, throat infections, airborne allergies, smoking, hearing problems, previous work as teacher or leader, vocally taxing hobbies, and previous voice therapy or voice training. A strong association was observed between the number of potential risk factors and voice symptoms. Risk factors were not related to the work environment because these students had not yet been exposed to teaching. In addition to teachers, recent studies have focused on soldiers, cantors, professional soccer managers, and fitness instructors. Dion et al. [8 ] analyzed 1.3 million health records of active duty US army soldiers with no history of dysphonia. Soldiers have occupational and environmental exposure, reduced hydration, hot dry climates, altered sleep patterns, and many other stressors. Voice is a key element in combat situations and a voice disorder may be dangerous. Soldiers were 1.13 times more likely to have dysphonia if they were deployed. A lack of association with diagnosis type, tobacco, and alcohol use indicates specific occupational exposures, warranting the implementation of preventive measures. Cantors [23] maintain a vocally intense lifestyle and have been largely underserved with regard to voice problems. These professionals face the challenge of both singing and teaching and present with &
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risk factors for developing dysphonia, including high vocal demands, reduced vocal downtime, allergies, and reflux. O’Neill and McMenamin [24] described voice use among professional soccer managers in Ireland and identified four variables related to increased risk for dysphonia: voice use, factors affecting voice change, impact of voice use, and the importance of voice at work. These risk factors were related to intense and prolonged voice use in poor acoustic environments and lack of vocal technique. Finally, Rumbach [25] reported on 38 Australian fitness instructors that revealed a lack of job satisfaction (65%) and emotional distress. The need to be more proactive is clear; however, critical epidemiological data are lacking.
COMMON PRESENTING SIGNS, SYMPTOMS, AND LARYNGEAL FINDINGS Vocal endurance seems to be more critical than vocal quality for many professionals. Flexibility can also be a particular requirement for some individuals such as the impersonators [9]; this variable has not been studied adequately. Symptoms in professional voice users do not always reflect awareness of a vocal problem and do not usually relate to decreased professional performance [7 ,13,26,27]. Symptomatology can be abundant [16 ,18,22] with no specific sign or symptom to clearly represent the main complaint of a professional voice user. Nevertheless, these individuals clearly link voice and/or discomfort with the workplace [16 ,18,28–30]. Discomfort with phonation is a key issue in teachers and may be the predominant symptom among these professionals [28,29]. The Voice Discomfort Scale [31] was employed to study teachers and revealed that discomfort was associated with diminished vocal self-assessment, but did not necessarily correlate with the degree of dysphonia [28]. Therapy can reduce the frequency and severity of discomfort symptoms quantified by this scale [29]. Pain during speaking in professional and nonprofessional voice users was studied in a large sample of 1152 Belgian individuals [32]. Significantly more pain symptoms were observed in professional voice users (84 vs. 55%). These symptoms were isolated to the throat, neck, shoulder, headache, ear, and back pain. Vocal training may play a role in reducing pain [33]. Recognition of the increased number of symptoms in the professional voice population is critical; however, as voice problems are typically chronic, increased symptoms do not lead to treatment seeking. The average number of symptoms necessary to motivate teachers to seek diagnosis and treatment &&
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was 8.6 [27]. Beyond the number and frequency of symptoms, recovery time following heavy vocal load appears to play a role in the perception of vocal dysfunction [34]. Interestingly, when student teachers were assessed [22], symptoms of discomfort during phonation were most common. Specific laryngeal information on student teachers reinforced the need for early intervention. Data from 30 first-year American acting students [26] revealed incomplete glottal closure (62%), hyperfunction (59%), decreased mucosal wave (55%), and findings of laryngopharyngeal reflux (48%). Similarly alarming data were reported for 79 first-year Israeli acting students [35], with 50% prevalence of aberrant laryngeal findings, and associated with auditory and acoustic deviations. Even if these findings are not life-threatening, they may cause stress, impair work conditions, and limit career longevity. An Australian fitness instructors group [30] presented with laryngeal disorder, even if working with amplification (80%), including vocal fold nodules (80%; N ¼ 30), cysts (6.6%), hemorrhage (3.33%), and recurrent chronic laryngitis (10%) in addition to vocal strain and muscle tension dysphonia. These professionals self-reported acute (78.95%) and chronic (70.91%) voice symptoms [25] as well as a negative impact of their voice on their lives, including social withdrawal, decreased job satisfaction, and emotional distress. Clearly, amplification does not ameliorate these issues. The Screening Index for Voice Disorder (SIVD) was proposed as an instrument of epidemiologic screening tool for teachers with voice problems [36]. It is not clear, however, how specific this instrument is with regard to teachers when compared with the general population or other professional categories. A critical lack of data regarding professional populations without voice problems remains problematic. A study of 72 American trained singers with no voice complaints [37] revealed a high occurrence of abnormalities on strobovideolaryngoscopy (86.1% of participants: laryngopharyngeal reflux, prominent varicosities or ectasias, incomplete glottic closure, and/or structural abnormalities) and acoustic analysis (deviated values from the norm in shimmer, relative average perturbation, and maximum fundamental frequency for female participants). These data must be considered when assessing a singer. Many predisposing factors in professional voice users have been described, such as lack of training, health-related problems, and psychological stressors [2,38,39]; however, none of these explain why certain people present with dysphonia, whereas others, under the same conditions, are more resilient.
Vocal behavior is usually considered an important risk factor; however, a recent Italian study of 92 callcenter operators using the ambulatory phonation monitor during a workday concluded that neither the number of working hours nor the percentage of phonation time was statistically related to the perception of voice disturbances [40 ]. A recent review regarding functional voice problems [41] proposed a cognitive behavioral model to deal with these patients. Individual factors (genetics, early experience, and personality), precipitating factors (life events and coping, vocal vulnerability), and perpetuating factors (anxiety, depression, and general fatigue) were proposed to be causative in voice problems. Even if this review did not focus specifically on professional voice users, it was clear that vocal vulnerability was the consequence of vocal load, which fits the current model of occupational voice demands. &
ASSESSMENT CRITERIA AND ASSESSMENT MEASURES Patients with voice problems are typically assessed by a multidisciplinary team consisting of an otolaryngologist and a speech-language pathologist. A singing specialist, voice coach, and/or psychologist may also be required. The European Laryngological Society proposed a standard assessment protocol for evaluating voice problems: perception, videostroboscopy, acoustics, aerodynamics, and subjective rating by the patient [42]. According to the American Academy of Otolaryngology–Head and Neck Surgery, the minimum battery to evaluate a patient with vocal complaint is clinical history, physical examination, and visualization of the larynx via laryngoscopy [43]. Specific procedures for screening, assessment, or follow-up of professional voice users have not been proposed. For the speech-language pathologist evaluation, auditory and acoustic analyses are fundamental to understand the underlying physiology. Moreover, the inclusion of self-assessment protocols to evaluate the impact of a voice problem is mandatory to help understand the relationship between the patient and his or her problem, to estimate adherence and coping, and to establish a prognosis [27,44]. Auditory analysis may not be reliable; a distorted voice may be characteristic of an actor, for example. Perception of the voice may not reflect discomfort during phonation; auditory assessment may underestimate the problem. Even if there is some evidence for selected acoustic, laryngeal imaging, auditory perceptual, functional, and aerodynamic measures to be used as effective components in a clinical voice evaluation [44],
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high-level research to provide evidence regarding these recommendations is warranted. Normative data for professional voice users and for aging professionals are also required [37]. Recently, an Italian group [45] proposed the use of the singing power ratio as an electroacoustic measure, correlated to both the years of singing activity and the vocal category of each singer. Moreover, it was highly correlated to clinician subjective assessment. Professional choir singers usually have a long career; to understand the difference between normal aging problems and the effect of the professional voice remains challenging [10]. Professional voice users may manipulate their voice to reduce the negative impact of a voice problem, which may pose difficulties in the evaluative process. The use of specific protocols for self-assessment of the singing voice was proposed [46–49] as a more sensitive tool, but data are limited. No specific protocols for professional speaking voice were proposed. In London, students of the arts seem to be at increased risk for voice problems as quantified by the VHI-10 [50]. Additionally, high scores were found in musical theater students (n ¼ 49) when compared with medical students (n ¼ 43), particularly in three specific domains: voice strain, lack of clarity, and being upset from voice problem [50]. It is difficult to interpret these findings as they may reflect awareness of a potential voice problem or initial symptoms due to a greater voice use over time. Regardless, the need for early laryngeal examination and voice evaluation of future professional voice users is enhanced by these findings. Even when employing a specific protocol, the S-VHI [51], musical theater singers perceived subtle fluctuations or changes in physical functioning of the voice that were not detected by the instrument. These symptoms became clear through a series of focus group interviews (n ¼ 43) and a written survey (n ¼ 36) to detail the perception of the impact of performing after a show, across a working week, and across a production season. A list of 97 descriptors was generated using the singers’ own terminology and experiences: symptoms of vocal impairment, vocal fatigue, and descriptors of positive vocal changes as a consequence of heavy vocal load. From this list, the 20-item Evaluation of the Ability of Singing Ease was created to assess the perceptions of healthy singers with regard to the singing voice as a function of vocal load [52 ]. This scale has potential to be included in clinical and performance settings. Behavioral evaluation of the professional voice usage in situ may offer important data nonreadily ascertained during the clinical consultation [40 ]; however, this protocol is likely often impractical. &
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Effectiveness of voice training and treatment programs Voice training focuses on vocal health, can potentially prevent voice problems, and is usually employed for improving normal voices for a specific demand, whereas treatment aims at correcting functional deficits. Training and therapy may use direct approaches (vocal exercises) and/or indirect strategies (relaxation, breathing techniques, and vocal hygiene information). Vocal hygiene is a component of almost all programs and some suggestions are common sense and have been used for more than one century [53]. Voice rest is an empiric treatment, but it is a challenge to select cases that can really benefit from complete silence. The concept of compounded and noncompounded phonotrauma may be used as a guide to predict success or failure of voice rest regimens; in complex phonotraumatic dysphonia, voice rest may be analogous to crash diets in the morbidly obese. However, in noncompounded cases, vocal rest may be a viable option [54]. Intervention studies are rare likely related to methodological complexity, which is even higher for professional voice users. Teachers and telemarketers have been the focus of the sparse literature to date. Osteopathic therapy, myofascial techniques together with voice exercises, relaxation, and aerobic activities apart from balneological treatment were used to treat 40 teachers with chronic vocal problems, in a health spa in Poland [55]. A reduction of tenderness and normalization of perilaryngeal tonus was observed. In spite of these favorable outcomes, the concept of a voice spa is difficult to implement elsewhere. The program proposed is too broad and the lack of a control group is problematic. Another study of 40 American female kindergarten and primary school teachers showed that the use of an individual, portable vocal amplification system reduced vocal fatigue and the degree of vocal deviation. Vocal dosage and intensity was also reduced with the use of a portable voice amplifier [56]. Participants maintained the reduced vocal intensity level after returning the amplification device. The telemarketing industry has become increasingly critical since the 1970s and it is one of the fastest growing businesses worldwide [7 ]. A representative effort in the UK proposed qualitative and quantitative research protocols applied to telemarketers and managers of 13 call centers [57]; poor vocal health habits and the lack of vocal training were common findings in this population and symptoms of reported muscle tension and voice problems had a marked impact on work. Specific training for all workers was recommended, particularly for those early in their career. A recent survey in India [14] &&
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analyzed 1093 call center workers from 11 centers. Data suggest the current prevalence of dysphonia was 59 and 27%, respectively, with female workers missing more days of work. The effectiveness of a voice training program was analyzed by comparing 14 Brazilian call center agents who underwent an 8-week training and 34 controls [58]. Unfortunately, the high rate of participant dropout in both groups was problematic. Perceptual analysis did not show improvement; however, jitter was consistently reduced after training, which can be considered an indirect measure of voice stability. More sensitive measures must be selected to better reflect improvement in professional voice users. In addition to training, real-time biofeedback seems highly promising. A prevention study was performed in Austria [7 ] with 76 call center operators. The study group used realtime biofeedback software (VidiVoice) for 4 weeks to improve vocal self-assessment and performance by monitoring fundamental frequency, intensity, and syllables per minute. Participants with vocal fatigue showed a larger voice range profile; moreover, all participants with hypofunction improved. This work tested the software in real-life situations, providing participants with the opportunity to optimize vocal performance at work. The effect of a 6-h voice training program (direct and indirect approaches) and a 30-min individual counseling session was investigated in 51 Belgian student teachers and 30 controls [59]. Several objective parameters improved in the training group, most significantly in female participants. The results support the effectiveness of this program and favor its introduction in the education of student teachers due to the already high prevalence of problems in this yet nonworking population [22,26,35]. Teachers usually consider their dysphonia as a part of their occupation [16 ] and a good strategy to improve adherence for these chronically dysphonic patients seems to be to offer the experience of an immediate change in vocal quality and/or discomfort with a simple exercise protocol [60]. It is complex to define an ideal voice for a professional user, particularly when considering the singing voice. A distorted ‘harsh’ voice can be quite valuable for a pop artist or heavy metal vocalist. However, this style can lead to a devastating voice disorder. Vocal rehabilitation for artists with intentional distortions should aim at a resilient and effective voice regardless of the sound [61]. It is possible to produce a healthy distorted sound for a specific market purpose, but no studies have focused on this issue. The cost-benefit ratio of providing therapy remains unclear and warrants further investigation. &&
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CONCLUSION The area of professional voice has grown with regard to our understanding of the specifics of the professional voice user. However, the main focus remains on teachers. Large population studies are needed and interventions targeting student teachers must be implemented to avoid frustration and chronic voice problems. However, a causative relationship between the workplace and voice disorders has yet to be established. Furthermore, longitudinal studies and randomized controlled trials are needed. Acknowledgements None. Conflicts of interest The authors declare no conflicts of interest.
REFERENCES AND RECOMMENDED READING Papers of particular interest, published within the annual period of review, have been highlighted as: & of special interest && of outstanding interest 1. Vilkman E. Voice problem at work: a challenge for occupational safety and health arrangement. Folia Phoniatr Logop 2000; 52:120–125. 2. Vilkman E. Occupational safety and health aspects of voice and speech professions. Folia Phoniatr Logop 2004; 56:220–253. 3. Schewell C. The daily working voice. Voice work: art and science in changing voices. Chichester: Wiley-Blackwell, 2010. 4. Titze IR, Lemke J, Montequim D. Populations in the US workforce who rely on voice as a primary tool of trade: a preliminary report. J Voice 1997; 11:254– 259. 5. Hunter EJ, Titze IR. Variations in intensity, fundamental frequency, and voicing for teachers in occupational versus non occupational settings. J Speech Lang Hear Res 2010; 53:862–875. 6. Epstein R, Remacle A, Morsomme D. From reactive intervention to proactive prevention: the evolution of occupational dysphonia. Perspect Voice Voice Dis 2011; 21:48–55. 7. Schneider-Stickler B, Knell C, Aichstill B, Jocher W. Biofeedback on voice && use in call center agents in order to prevent occupational voice disorders. J Voice 2012; 26:51–62. This study introduced biofeedback software into a real-life call center workplace situation and proved that it is possible to monitor vocal parameters and to improve vocal awareness and performance while working. 8. Dion GR, Miller CL, Ramos RG, et al. Characterization of voice disorders in & deployed and nondeployed US army soldiers. J Voice 2013; 27:57–60. This is the largest cross-sectional study in the voice area; more than 1.3 million health records were analyzed; occupational exposure of deployed soldiers accounts for the increase in the diagnoses of dysphonia. 9. Revis J, De Looze C, Giovanni A. Vocal flexibility and prosodic strategies in a professional impersonator. J Voice 2013; 27:524; e23-31. 10. Berghs G, Creylman N, Avaux M, et al. A lifetime of professional singing: voice parameters and age in the Netherlands Radio Choir. Logoped Phoniatr Vocol 2013; 38:59–63. 11. Szeszenia-Dabrowska N, Wilczynska U. Occupational disease in Poland: an overview of current trends. IJOMEH 2013; 26:457–470. 12. Warhurst S, McCabe P, Madill C. What makes a good voice for radio: & perceptions of radio employers and educators. J Voice 2013; 27:217–224. This is a well presented qualitative study that focuses on the educators’ and employers’ opinions on the needed characteristics of voices for radio; this approximation between science and market is much needed in the professional voice area. 13. Piwowarczyk TC, Oliveira G, Lourenc¸o L, Behlau M. Vocal symptoms, voice activity and participation profile and professional performance of call center operators. J Voice 2012; 26:194–200. 14. Devadas U, Rajashekhar B. The prevalence and impact of voice problems in call center operators. J Laryngol Voice 2013; 3:3–9. 15. Cutiva LCC, Vogel I, Burdorf A. Vocie disorders in teachers and their associations with work-related factors: a systematic review. J Commun Disord 2013; 46:143–155.
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Volume 22 Number 3 June 2014
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