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Occupational Voice: Care and Cure

edited by: P.H. Dejonckere

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Publication details: Book. 2001. xii and 207 pages. Publication date: 2001-03-23. 67 figures and28 tables. Hardbound. 16x24 cm (6.3x9.4 in).

ISBN: 978-90-6299-179-2 (ISBN 10: 90-6299-179-3; Kugler Publications)

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The concept of occupational voice disorders
Philippe H. Dejonckere

"People using their voice professionally are at risk for occupational voice diseases, and require specific prevention and treatment" was the topic focused on by the third Pan European Voice Conference, organized in August 1999 at Utrecht University. The present book includes the main tutorial lectures, with reviews of the most relevant research data and opinions regarding this specific area of concern. Occupational voice users include not only singers and actors, but also teachers, politicians, lawyers, clergymen, telephone operators, etc.(1). The pathogenesis of voice disorders in such patients can be primarily related to their occupation, and thus, after adequate differential diagnosis, these need to be recognized as true occupational diseases, in the same way as, for example, occupational hearing loss (2). A surfeit of information is available on the potential damage from exposure to excessive noise levels(3,4). Noise-induced hearing loss is generally recognized as a typical occupational disease. The relationship between dose and effect is clear, as is documented in publications by the International Organization of Standardization (ISO) (5). The dose combines intensity and duration, and therefore, the concept of dosimetry is of major importance. Also of importance is the definition of the safe limits for exposure to noise. However, factors regarding individual susceptibility to noise and the reversibility of early effects also have to be considered, as well as possible preventive indices of noise-induced hearing loss (6). In some - but not all - respects, noise-induced hearing loss may be considered as a useful model for occupational voice disorders. 


Titze (7) compared the percentage of the US working population and of the voice-clinic load for different occupation categories: for example, telephone marketers constitute only 0.78% of the total workforce, but 2.3% of the clinic load; teachers represent 4.2% of the US workforce and 20% of the voice-clinic load. Studies based on questionnaires have suggested that teachers and aerobic instructors are at high risk for disabilities from voice disorders, and that these health problems may have significant work-related and economic effects (8,9). For example, Russel et al.(10) investigated the prevalence of self-reported voice problems in teachers: 16% of teachers reported voice problems on the day of the survey, 20% during the current teaching year, and 19% at some time during their career. Roughly speaking, we can conclude from the several studies published during the 1990s that about 20% of teachers experience voice disorders (11).

Voice dosimetry

Objective measurement of vocal use and vocal load is necessary for the identification of activities and working conditions that are at risk. Voice dosimeters can provide information on the total vocalization time and sound pressure level over a whole working day, in a real life situation (12-14). Just as noise dosimeters define acceptable levels of noise exposure, voice dosimeters help to define the average acceptable limits for vocal load. 


Repeated mechanical vibrations transmitted to the body tissues by engines or machines are known to be able of eliciting - in certain conditions - specific kinds of pathology, which are also considered to be occupational diseases (15,16). The vibration may involve the whole body (e.g., in a vehicle) or mainly the hand, wrist, elbow, or shoulder (hand-held power tools). There are standards in the field of occupational health that stipulate the acceptable limits for tissue acceleration values, depending on the frequency (17). Titze's calculations suggest that the risk of damage from tissue vibration is exceeded by occupational vocalists, such as telephone marketers and teachers (18). In the last few years, much new and important information has materialized on the dangers of 'hyperphonation', i.e., loud and prolonged phonation beyond the physiological range. Laboratory experiments on canine larynges, hyper-phonated in vivo under anesthesia, demonstrated obvious damage to vocal fold epithelia (19). The basement membrane shows early lesions and seems to be particularly sensitive (20). A clinical study by Mann et al.(21) in drill sergeants, demonstrated significant increases in vocal fold edema, erythema and edge irregularity, and decreases in vocal fold mucosal wave and amplitude of excursion, following a five-day training period

Voice fatigue, relief and recovery

According to Titze (18) , two different aspects must be considered:

  1. Muscle fatigue: the muscle chemistry needs to be reset for the following contractions.

  2. Epithelial cells may die and be shed, due to repeated traumata. New cells have to develop underneath. Collagen and elastin fibers may have separated from the structural matrix of the lamina propria, and have to be removed and replaced by the fibroblasts. Detached protein debris will be removed and re-used by the fibroblasts to make new protein fibers that will support the connective tissue structure. Therefore, minor destruction and repair is continuous.

Can the regenerative processes keep up with the destructive process, and what are the physiological time constants in these processes? When there is damage to the joints, ligaments, tendons, or other connective tissue, the recovery time will be proportional to the amount of localized tissue injury that has occurred. If muscle fatigue is the only complaint, the recovery period required will probably be shorter. Hypothetical curves for tissue injury and the recovery period for human phonation have been suggested by Titze (18). Nevertheless, vocal fatigue is still difficult to identify in practical and clinical situations, and Buekers has questioned the clinical relevance of voice endurance tests (13,14).

Environmental factors

The relative humidity of the air affects vocal function: the most common subjective complaints of teachers with regard to their working environment are the dryness and dustiness of the air. Professional singers note that singing is more difficult in a dry environment: dry air puts an increased strain on the phonatory apparatus and raises the demands on its efficacious and appropriate use (22). The human voice is very sensitive to decreases in the relative humidity of inhaled air because, in experimental conditions, even after short provocation, a significant increase in perturbation measures has been found (23). Noise is also a very common and relatively well-known risk factor in the working environment of professional voice users. It has been observed that the sound level of the speaking voice significantly increases in ambient noise levels starting from 40 dB (A) (about 3 dB for each 10 dB increase in ambient noise), due to the Lombard effect (24,25). In kindergartens, for example, noise levels have been found to vary between 75 and 80 dB (A) (26,27). 

Effects of stress

Mendoza and Carballo investigated the effects of experimentally induced stress on voice characteristics (28). In conditions of stress, induced by means of a stressful environment and cognitive workload tasks, they observed: 
1. an increase in F o with respect to baseline;
2. a decrease in pitch perturbation quotient and in amplitude perturbation quotient;
3. a lower presence of turbulent noise in the spectral zone in which the existence of harmonic components is not expected (2800-5800 Hz), with respect to harmonic energy in the 70-4500 Hz range;
4. an increase in harmonic energy in the 1600-4500 Hz range with respect to harmonic energy in the 70-1600 Hz range.

The increase in F o seems to be considered a universal indicator of stress and of cognitive workload, as is the lowering of F o perturbation. The response to a stressful stimulus demands a high level of activation, which in turn produces elevated ergotropic arousal that would cause an increase in the tension of the vocal muscles, producing a higher and more tense voice. Mattiske et al. (29) report that teachers seem to experience a significant degree of stress during their work (30) , and there is some research evidence that anxiety and stress are associated with the development of voice problems (31). Marks (32) compares teachers' voices with those of nurses, and finds that psychological stress is reported more frequently by teachers. There are indications that stress, psychological tension, personality, and other psychological factors, may play an important role in voicing problems among teachers (30,33,34).

Vocal fold lesions

Phonotrauma may result in typical vocal fold lesions, to be interpreted as a direct consequence of mechanical stress and/or as tissue reaction to that stress. Vocal fold nodules and polyps are classical examples (35,36) , but also contact ulcerations/ granulomas of the vocal processes (35,36,37) , if not induced by acid re-flux. Vocal fold hemorrhage is generally consecutive to acute phonotrauma (35). Depending on reversibility and context, microsurgery may become indicated as an important element of the treatment (38,39).

Care and cure

Patients with occupational voice disorders should benefit from specific medical and paramedical treatments, as well as from technical aids, with respect to their particular pathogenesis. There are major economical aspects at stake, and occupational rehabilitation plays an important role. In a few cases, compensation and professional re-orientation is necessary. Outcomes of the various possible treatment strategies have still to be investigated. However, prevention is still essential. There are indications that vocal hygiene education programs could improve the voice by reducing vocal abuse in daily life and by practising specific strategies to maintain classroom order and to reduce the use of the voice during teaching (40). Further research is needed to demonstrate the usefulness of prevention strategies on the incidence of actual voice disorders.


1. Irving RM, Epstein R, Harries MLL: Care of the professional voice. Clin Otolaryngol 22:202-205, 1997

2. Dejonckere PH: The concept of 'occupational voice'. In: Dejonckere PH, Peters H (eds) Communication and its Disorders: A Science in Progress, Proceedings of the 24th IALP Congress Amsterdam, 1998, Vol 1, pp 177-178. Nijmegen, NL: Nijmegen University Press 1999

3. Sataloff RT, Sataloff J: Occupational Hearing Loss, 2nd Edn. New York, NY: Marcel Dekker 1993

4. Kryter KD: The Handbook of Hearing and the Effects of Noise. New York, NY: Academic Press 1994

5. ISO-1999: Acoustics: determination of occupational noise exposure and estimation of noise-induced hearing impairment. Geneva: International Organization of Standardization 1990

6. Chon KM, Roh HJ, Goh EK, Wang SG: Noise induced hearing loss and the individual susceptibility to the noise. Int Tinnitus J 2:73-82, 1996

7. Titze IR: Populations in the US workforce who rely on voice as a primary tool of trade: a preliminary report. J Voice 11:254-259, 1997

8. Smith E, Lemke J, Taylor M, Kirchner HL, Hoffman H: Frequency of voice problems among teachers and other occupations. J Voice 12:480-488, 1998

9. Newman C, Kersner M: Voice problems of aerobics instructors: implications for preventative training. Log Phon Vocol 23:177-180, 1998

10. Russel A, Oates J, Greenwood KM: Prevalence of voice problems in teachers. J Voice 12:467-479, 1998

11. Simberg S, Laine A, Sala E, Rönnema AM: Prevalence of voice disorders among future teachers. J Voice 14:231-135, 2000

12. Masuda T, Yoshimitu I, Manako H, Komiyama S: Analysis of vocal abuse: fluctuations in phonation time and intensity in 4 groups of speakers. Acta Otolaryngol (Stockh) 113:547-552, 1993

13. Buekers R: Voice Performances in Relation to Demands and Capacity. PhD Thesis, Maastricht 1998

14. Buekers R: Voice endurance tests and vocal fatigue. Clin Otolaryngol 23:533-538, 1998

15. ILO (International Labour Office): Encyclopedia of Occupational Health and Safety, 3rd Edn. Geneva: Luigi Parmeggiani Ed 1983

16. Dejonckere PH: Occupational voice disorders. In: ILO Encyclopedia of Occupational Health and Safety, 3rd Edn. Geneva: Luigi Parmeggiani Ed 1983

17. Griffin MJ: Handbook of Human Vibration. San Diego, CA: Academic Press 1990

18. Titze IR: Toward occupational safety criteria for vocalization. Log Phon Vocol 24:49-54, 1999

19. Gray SD, Titze IR, Lusk RP: Electron microscopy of hyperphonated vocal cords. J Voice 1:109-115, 1987

20. Gray SD: Basement membrane zone injury in vocal nodules. In: Gauffin J, Hammarberg B
(eds) Vocal Fold Physiology. San Diego, CA: Singular Publishing Group Inc 1991

21. Mann EA, McClean MD, Gurevich-Uvena J, Barkmeier J, McKenzie-Garner P, Paffrath J, Patow C: The effects of excessive vocalization on acoustic and videostroboscopic measures of vocal fold condition. J Voice 13:294-302, 1999

22. Sundberg J: The Science of the Singing Voice. De Kalb, IL: Northern Illinois University Press 1986

23. Hemler R, Wieneke G, Dejonckere PH: The effect of relative humidity of inhaled air on acoustic parameters of voice in normal subjects. J Voice 11:295-300, 1997

24. Van Heusden E, Plomp R, Pols LCW: Effect of ambient noise on the vocal output and the preferred listening level of conversational speech. Appl Acoust 12:31-43, 1979

25. Dejonckere PH, Pépin F: Study of the Lombard effect by measuring equivalent sound level. Fol Phoniat 35:310-315, 1983

26. Truchon-Cagnon C, Hétu R: Noise in day-care centers for children. J Noise Control Engin 30:57-64, 1988

27. Vilkman E: Occupational risk factors and voice disorders. Log Phon Vocol 21:137-141, 1996

28. Mendoza E, Carballo G: Acoustic analysis of induced vocal stress by means of cognitive workload tasks. J Voice 12:263-273, 1998

29. Mattiske JA, Oates J, Greenwood KM: Vocal problems among teachers: a review of prevalence, causes, prevention and treatment. J Voice 12:489-499, 1998

30. Russel DW, Altmaier E, Van Velzen D: Job related stress, social support and burnout among classroom teachers. J Appl Psychol 72:269-274, 1987

31. Green G: Psycho-behavioral characteristics of children with vocal nodules: WPBIC ratings.
J Speech Hear Disord 54:306-312, 1989

32. Marks JB: A Comparative Study of Voice Problems among Teachers and Civil Service Workers. Thesis. The University of Minnesota 1985

33. Calas M, Verhulst J, Lecoq M, Dalleas B, Seilhean M: Vocal pathology of teachers. Rev Laryngol (Bordeaux) 110:397-406, 1989

34. Cooper M: Vocal suicide in teachers. Peabody J Educ 47:334-337, 1970

35. Gould WJ, Rubin JS, Yanagisawa E: Benign vocal fold pathology through the eyes of the laryngologist. In: Rubin JS, Sataloff RT, Korovin GS, Gould WJ (eds) Diagnosis and treatment of voice disorders. New York, NY: Igaku-Shoin 1995

36. Titze IR: Principles of Voice Production. Englewood Cliffs, NJ: Prentice Hall 1994

37. Nagata K, Kurita S, Yasumoto S, Maeda T, Kawasaki H, Hirano M: Vocal fold polyps and nodules. Auris Nasus Larynx 10 (Suppl):37-45, 1983

38. Bouchayer M, Cornut G: Microsurgical treatment of benign vocal fold lesions: indications, techniques, results. Folia Phoniatr 44:155-184, 1992

39. Cornut G, Bouchayer M: Phonosurgery for singers. J Voice 3:269-276, 1989

40. Chan RWK: Does the voice improve with vocal hygiene education? A study of some instrumental voice measures in a group of kindergarten teachers. J Voice 8:279-291, 1994

Table of Contents

Table of Contents

Introduction: The concept of occupational voice disorders P.H. Dejonckere

Criteria for occupational risk in vocalization I.R. Titze

Gender differences in the prevalence of occupational voice disorders. Some anatomical factors that possibly contribute P.H. Dejonckere

Voice dosimetry R. Buekers

Room acoustics. How they affect vocal production and perception D.M. Howard and J.A.S. Angus

Phoniatric fitness examinations. Evaluation of long-term experiences W. Seidner and J. Wendler

Voice in the classroom. A re-evaluation V. Morton and D.R Watson

Air pollution and environmental factors. Their importance in the etiology of occupational voice disorders R.E. Chavez C. de Bartelt

Performance stress in professional voice users W.A.R. Wellens and M.J.M.C. van Opstal

Predictive parameters in occupational dysphonia. Myth or reality? F.I.C.R.S. de Jong, P.G.C. Kooijman and R. Orr

Occupational voice disorders and the Voice Handicap Index T. Murry and C.A. Rosen

A survey on the occupational safety and health arrangements for voice and speech professionals in Europe E. Vilkman

The spirit of laws on occupational diseases. Historical background and comparative overview of European legislations J. Ugeux

The challenge of determining work-related voice/speech disabilities in California. A multi-disciplinary laryngology and voice pathology evaluation K. Izdebski1, E.D. Manace and J.S. Haris

Basic elements in voice therapy. A system for indexing and quantifying the contents of the functional approach, particularly in occupational voice disorders P.H. Dejonckere and G.H. Wieneke

Theoretical and practical considerations in the occupational use of voice amplification devices J.A. McGlashan and D.M. Howard

Treatment outcomes in occupational voice disorders J.K. Casper

Medico-legal impairment and invalidity in different American and European countries P.H. Dejonckere

Index of authors

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