Chapter 1
Introduction to Clinical Voice Disorders
It is impossible to know the fundamentals of a phenomen on without having solid knowledge of its origin, development and the chain of causes, conditions and circumstances determining its actual existence
-Kiml
The Functions of the Larynx in Living Creatures
The larynx lies at the crossroads of life, a barometer of our physical and mental health, an airway through which flows life-sustaining oxygen, and a valve that protects the lungs from ingestion of foreign substances. When its powerful musculature shuts off the airway, air can be impounded in the lungs, forming a rigid thorax to support firmly the attached upper extremities during lifting and pushing. Bearing down during laryngeal closure compresses the abdominal contents for defecation, micturition, and parturition and fixation of the thoracic cage for coughing, throat clearing, and vomiting. Yet, as vital as these functions are, the larynx manages to shift deftly from protector of life to communicator, generating raw sound for articulation of intellect and as a prosodic background to language informing the outside world of its owner's personality, emotional state, and cultural heritage. It is a somewhat daunting task to attempt to write a book that provides the bases for voice assessment and treatment of this formidable organ. The mechanics of speech require integration of the respiratory, phonatory, resonatory, and articulatory musculature. Although the emphasis of this book is on voice production, we consider herein, for the most part, components of the total speech act: respiration, the power and driving force of sound; phonation, sound generated by rapid vocal fold movement driven by the exhaled air stream; and resonation, modification of the raw sound generated by the larynx by movement of the other articulatory structures including the velopharyngeal complex.
The larynx is a complex organ composed of cartilage, muscles, nerves, and connective tissues. The vocal folds themselves, the source of sound, are made of layers of laminated tissue, with a muscular layer in the innermost part of the folds and progressively thinner layers of softer tissues toward the epithelium. During vocalization, cells from the skin layer are destroyed and sloughed off. Vocalization causes cellular and extracellular damage to vocal fold tissues, which the body can repair with time. Factors such as genetic predisposition, internal and external vocal tissue environment, physical and mental health, and quantity and quality of vocal use are thought to contribute to the recovery rate of injured vocal fold tissue.
An important and unusual fact about the larynx is that phylogenetically it is eons older than those brain and muscle structures responsible for articulation and language. The latter are synonymous with the intellect, itself a recent vertebrate acquisition, but the larynx and voice owe a disproportionately strong allegiance to the primitive emotions, persuasive proof of which can be found in everyday experience, during emotional arousal. When we are incapable of preventing loss of cortical control over the larynx, it escapes our grasp and drags us back into its primeval depths as we laugh, cry, scream, groan, or are rendered voiceless. Have we not often witnessed such loss of intellectual speech expression as in the following experience? A professor of law, known for his razor-sharp tongue and habit of taunting and ridiculing students (who, incidentally, loved him in spite of it), rose to speak at a farewell banquet:
He stood motionless for a long time. We observed that his face was different than we had ever seen it before. It had lost its severity. It was flushed and looked pink and kind. The mouth was not a snarl. His voice, too, was different. It was soft without a trace of belligerence or sarcasm. "I cannot bid you all goodbye and leave unsaid that which is the most important thing in my life." He took a deep breath and continued, his voice hoarse with emotion. It grew hoarser as he struggled to eliminate the quiver, which was entering it. He then paid tribute to his lovely wife. "I cannot in this leavetaking do other than tell you that I owe all my happiness to her, that she has." He turned. Tears were running down her cheeks. Their gazes met and locked in long silence. Then without another word, he sat down" (Nizer, 1978).
We are fascinated by the mystery of how speech and language evolved in the kingdom of the vertebrates and have struggled with a basic question: Are the structure and sound-generating properties of the human larynx mere extensions of its role in lower vertebrates, the ultimate in evolutionary refinement for the expression of ideas? That is to say, is the Darwinian belief correct, that speech is not a product of special creation but only another form of sound-making, more sophisticated because of a quantitative increase in human intelligence? Or, is speech uniquely human, de novo, different in kind, not degree, from lower animals? The answer is unknown.
Another, perhaps only slightly less difficult, question is this: Is it the monkey's and chimpanzee's intellect or anatomy that prevents speech in these primates? Some argue that the primitiveness of their laryngeal and articulatory anatomy stands in the way of speech, yet the larynges of the monkey and chimpanzee are remarkably similar in structure and method of sound production to those of humans. The fact is that human speech is not dependent upon a particularly refined larynx, for speech continues despite laryngeal tumor, paralysis, and even total laryngectomy, whereupon the esophagus or even an electronic sound generator can assume the responsibility for sound-making. Most scientists now concur that before primates could talk, a high level of abstract intelligence was required as the governing force.
A universal fact about the world of living creatures is that almost all make sounds. Insects tap surfaces, snap or rub their wings, or rub leg against wing, as in the case of the grasshopper, producing complex trains of pulses that send messages of courtship and sexual recognition. Admittedly, many lower forms produce sound accidentally, but most do so for a purpose; survival-signaling fear, aggression, mating, territoriality, and pleasure. Situation-specific use of voice in birds, for example, has been firmly categorized into mating, distress, fear, anger, terrorizing, and triumphal calls.
Negus (1929) observed that individual living creatures produce sound as both defense and offense: intimidation, cries for help and food, and decoying of prey. Sound brings and keeps the sexes together for survival of the species, attracting and repulsing the opposite sex, and protecting offspring. Sound further enables each species to keep in touch when out of sight, as in grass, in trees, at night, and in lairs or burrows. Sound also aids in the conveyance of special ideas, such as cooperation, calls to food and migration, and entertainment.
Human phonation is linked to much more than the intellectual act of speech. The human voice serves similar sublinguistic purposes of survival. The larynx is an important escape valve for the emotions-anger, grief, and affection-which are essential to the maintenance of our psychologic equilibrium.
Definitions of Terms
Voice
We need to define terms used constantly in the field of voice disorders. To begin with, voice is an auditory perceptual term that means the audible sound produced by the larynx, which embodies such parameters as pitch, loudness, quality, and variability.
- Pitch is the perceptual correlate of frequency.
- Loudness is the perceptual correlate of intensity.
- Quality is the perceptual correlate of complexity.
- Variability is the perceptual correlate of variations of the above parameters.
Phonation
- Phonation is the physical-physiologic act of sound production: the oscillations of the vocal folds driven by the exhaled air stream. Clinical terms denoting abnormal voice are dysphonia, aphonia, and muteness.
- Dysphonia describes any voice that sounds abnormal in its psychoacoustic parameters of pitch, loudness, quality, and variability; for example, excessively high or low pitch, inadequately or excessively loud voice, aberrant quality such as hoarseness, or breathiness or voices lacking in variability and as monopitch or in some patients excessive variability.
- Aphonia refers to the absence of a laryngeal tone: sounds like whispered speech or an extreme degree of breathiness.
- Muteness is a word to describe the patient who has no voice or articulation.
Normal Voice
Frequently asked is, what is a normal voice? Johnson, Brown, Curtis, et al. (1965) listed several criteria:
- Quality must be pleasant, with a certain musical quality and an absence of noise, inappropriate breaks, voice perturbations, or atonality.
- Pitch must be appropriate to the age and gender of the speaker.
- Loudness appropriate to the communication event, not so weak as to be borderline intelligible or unintelligible under ordinary speaking circumstances, not so loud that it calls attention to itself, and appropriately adjusted to the context of the event be it for confidential communication, speaking in a large lecture hall, or yelling for help
- Adequate flexibility Pitch and loudness variations are available to express emphasis, meanings, or subtleties...
