There are many ways in which a person’s voice can be disordered, perhaps one of the most well known being laryngitis. Yet, the most severe form of a voice defect is a disorder called aphonia. This means that the person has completely lost all ability to use their voice. How does this happen?
There are various reasons why aphonia can occur. One cause is the inability for the person’s vocal folds to approximate (get close together) enough for air pressure to build up under them. This is a problem because the build up of air pressure is what causes the folds to open and be set into vibration. Therefore, if no pressure is present, the folds will not vibrate adequately, and no sound will be produced.
A person’s inability to approximate their vocal folds can be caused by either paralysis of the muscles that bring one or both of the vocal folds together or by a large growth, such as a tumor on or between the folds that prohibits them from closing enough to vibrate.
Another reason aphonia occurs is because of the complete absence of one or both of the vocal folds because they have been surgically removed. The most common reason for this procedure (laryngectomy) is laryngeal cancer. In this case, surgery may be an option to restore the ability to speak, but if it is not or the person would rather go another route, there are different devices and alternative modes of speaking.
One mode is through the use of a device called an electrolarynx. This is a small handheld battery-powered electrical device that a person can place below their chin. When pressed against the skin, it vibrates causing the skin and underlying structures to vibrate. This causes the air molecules in the oral and nasal cavities to vibrate as well, which produces the vibrations necessary to produce speech.
There are two other alternate approaches to speaking that require nothing but a person’s esophagus or trachea. These modes are called esophageal speech and tracheo-esophageal speech. In order to make efficient use of esophageal speech, one must learn to release gas from or through the esophagus, like when burping. They must then use the vibrations created by this process to create speech. The vibrations from the esophagus are simply replacing the normal method of using laryngeal vibrations for speech production.
Tracheo-esophageal speech is another alternative speaking method in which air is passed from the lungs to the esophagus via a small opening in the wall the separates the trachea and esophagus. The process for producing speech is the same as for the esophageal speech. The difference between the methods is simply the way in which the air is released into the esophagus.
Another cause of aphonia is that sometimes a person’s vocal folds may be too stiff due to the presence of scar tissue or swelling. This creates folds that are incapable of vibrating, and therefore, unable to create voice.
Sometimes the cause of aphonia may not be physically evident. This means that the structure and function of the vocal folds are in normal condition, but the person’s voice is still absent. A person exhibiting this behavior will most likely be diagnosed with hysterical aphonia. This just means that the person is unable to use their voice due to psychological reasons. A person with this condition may benefit from psychotherapy.
Sources:
Silverman, Franklin H. Essentials of Speech, Language, and Hearing Disorders. Cincinnati: Atomic Dog, 2003.
http://en.wikipedia.org/wiki/Mechanical_larynx
