The voice is nothing but beaten air
Seneca (Lucius Annaeus Seneca), Naturalinum Quoestionum (bk. II)
DESPITE THE FUNDAMENTAL SIMPLICITY of the vocal mechanism, it holds extraordinary power. While an expressive, confident, engaging voice is extremely useful in most areas of life, a tired, lackadaisical voice can have equally damaging impact on a persons social interactions and self-esteem.1 Voice function also can have a sizeable social and economic impact; in November 2004, the TUC, Britain's congress of trades union, stated the UK economy was losing an estimated £200m a year because of voice problems among workers.2 The prevention of voice problems has a psychological, medical, social, and economic rationale.
But what is the nature of these problems? The most commonly reported voice problem is vocal fatigue, typified by effortful phonation and a self-perceived tired, weak voice.3 It tends to be related to specific vocal behaviors, including misuse and overuse of the voice. Recently, a number of authors have assessed the impact of vocal fatigue within different occupational environments.4
How can voice problems be prevented? We all have intuitive ideas about what types of behavior are "good for the voice." Singing websites advocate a range of "vocal hygiene" (VH) measures that do not appear to be based on any empirical findings. However, evidence does exist that the speech and language therapist has an important role in supplying vocal hygiene advice to a range of groups susceptible to voice problems, including professional actors, singers, and teachers.5
In clinic, a range of measures often is recommended to those complaining of vocal problems, including various voice supporting measures such as direct steam inhalation, ambient humidification, and ingestion of mucolytics (drugs that thin the mucus lining of the laryngeal mucosa). Conversely, it is advised that certain behaviors are avoided that will tend to "dry out" the voice, including, smoking, drinking alcohol and caffeine, and spending time in smoky or dusty environments. While a number of pharmacological agents have detrimental effects on voice production, avoidance of these agents is not part of the standard vocal hygiene regimen, except in the case of caffeine. Avoidance of caffeine is a feature of the advice given out not only by speech and language therapists, but also by teachers of singing and other voice "experts." Despite the prevalence of this advice, it seems only a limited amount of scientific work has been done to link caffeine ingestion with changes in voice quality.6
Why does VH advice take the form it does? While empirical data may have played a significant role in originating VH advice, it seems likely that historical and anecdotal factors account for some aspects of vocal hygiene behavior. For example, there is a popularly held belief that milk intake is detrimental to voice quality because of effects on mucus production;7 however, a Medline search produced no clinical data that assessed the impact of milk on voice production. A complex meshwork of historical factors and anecdotal evidence appears to have originated much of today's frequently used VH advice. This is especially the case among singers, where the practice of a vocal warm-up is usual before a performance. Despite the undoubted popularity of vocal warm-ups, there is as yet only a limited understanding of what is going in the larynx physiologically as the voice "warms up." AU in all, behaviors invoked as being "good for the voice" by the scientific community and others do not seem to carry a large body of scientific data. This does not represent an ideal situation; a rigorously tested program of "evidence-based" vocal hygiene advice would be preferable to a situation where some advice appears to lack a significant basis in experimental fact. Thorough programs of research in this area have been hampered by the confounding effect of different levels of training among study participants; voice function varies considerably with the amount of vocal experience a person has. …