How do humans produce voice?
What is voice therapy?
Voice or vocalization is generated by air forced by the lungs up and through the windpipe (trachea) and the larynx (voice box). As air passes the true vocal folds (vocal cords), a reduction in air pressure above the folds (known as the Bernoulli Effect) — combined with the springiness of the folds and the voluntary closure and muscle tension of the folds — produces a sound (a vibration of air).
The Bernoulli Effect is the same effect that occurs over the wings of an airplane allowing flight. The sound produced by the vibrating vocal cords is shaped and filtered by the articulators of the vocal tract above the larynx. The articulators include:
To best appreciate the complexity of the human voice, one should understand that the vocal tract extends from the diaphragm (the muscle that contracts and relaxes to produce breathing in and out) to the lips.
What is voice rehabilitation?
Voice therapy is performed by a speech-language pathologist who is licensed to diagnose and treat disorders of the voice. These may range from simple hoarseness to the complete inability to produce sound. Many voice disorders are brought on by the incorrect use of the voice, placing demands on the vocal cords that cannot be withstood without damage to the delicate lining of the cords.
Voice disorders are more common in people who must speak a great deal in the course of their work, such as teachers or ministers. Many of these groups develop their voice impairment when forced to speak during an upper respiratory infection or allergy attack. Speech-language pathologists retrain individuals in the correct use of the voice to minimize these problems and prevent them from recurring.
Certain voice disorders arise as part of a disease involving the respiratory tract. Speech-language pathologists are highly trained in diagnosing the causes of voice disorders and may refer the patient to a physician specialist such as an otolaryngologist (an ear, nose and throat specialist) in cases where disease may be the cause of the voice disorder.
I am hoarse often. Should I be concerned?
Often in the course of disease or treatment for disease, especially head and neck cancer, the structures that produce voice are affected. Our speech-language pathologists have special and vast experience in a coordinated program of voice therapy for patients who have diseases that affect speech or have anatomical changes from surgery that have impaired speech. With the most modern diagnostic techniques, they can pinpoint the particular problem and begin a specific course of treatment to return the patient's normal, or at least acceptable, voice production.
For those patients who have lost the larynx (voice box) to cancer (total laryngectomy), our speech-language pathologists are well versed in all of the modern techniques for returning voice to patients who no longer have one, enabling astounding communication abilities despite not having a larynx.
What are swallowing disorders?
Hoarseness of the voice that lasts for over one week and is not associated with an obvious infection in the area (sinusitis, a sinus infection) or cold should be evaluated by an ear, nose and throat specialist. Usually, hoarseness may be due to allergies or reflux of stomach acid back up the esophagus, causing irritation of the vocal cords (gastroesophageal reflux disease or GERD).
Occasionally, it may be due to a benign growth on the vocal cord known as a polyp. These must be surgically removed by passing a scope through the mouth and removing the polyp through the scope. Polyps have a habit of frequently growing back after removal if the cause of their appearance is not corrected.
A surgeon will often consult a speech-language pathologist to teach the patient a different way of speaking that does not place so much stress on the vocal cords, a factor that is thought to play a role in their growth. A vocal cord polyp has ruined some professional acting and singing careers, so it is worthwhile to get vocal therapy to complement your treatment for polyps.
A more serious cause of persistent hoarseness is a malignant growth on the vocal cord or fold. If these are diagnosed early, these types of cancer are very curable. The key is not to ignore the symptom of hoarseness, but to have it evaluated quickly.
What is an example of how a swallowing disorder would be diagnosed?
Swallowing disorders refer to any impairment of the ability to swallow normally. They range from trouble propelling food to the back of the throat to food getting stuck in the esophagus (the tube that connects the throat to the stomach).
Symptoms may also include coughing with swallowing, which indicates that food, liquid or saliva has gone into the windpipe (trachea) instead of the esophagus, a condition known as aspiration. Aspiration may result in recurring bouts of pneumonia (a serious lung infection) and may cause death by airway obstruction. Problems with swallowing that are more than very occasional almost always signal that something is seriously wrong.
Possible causes of problems swallowing range from tumors of the throat and esophagus to degenerative diseases of the nervous system. The most common cause of a swallowing disorder is a stroke. Speech-language pathologists are able to offer highly sophisticated techniques to diagnose the exact cause and location of the swallowing problem and recommend a course of treatment.
The above is by no means a complete list of questions that patients may have. Patients with concerns or questions are urged to contact the Center for Voice and Swallowing Disorders directly for more information.
How do swallowing disorders occur?
For example, a teacher notes having developed dysphonia six months after receiving a general anesthetic for a hysterectomy. This sequence of events implies a slowly evolving change in the larynx after surgery, which most likely required the placement of an endotracheal tube (a breathing tube placed within the larynx to ventilate the patient).
Continuing with the evaluation of the patient, the physician would perform an initial examination of the head, ears, nose, throat and neck. Next the larynx would be directly visualized during quiet breathing and vocalization using an endoscope.
In this hypothetical patient, the history suggests the endotracheal tube irritated the mucous membrane over the arytenoid cartilages (the largest of three cartilages located within the posterior or back portion of the true vocal folds on which the endotracheal tube may have rested).
How do humans swallow?
Swallowing disorders can occur in any of the three phases of swallowing, and may be the result of weakness or paralysis of muscles, loss of sensation, injuries, and surgery or tumors.
For example, in the oral phase, drooling due to inability to close the lips after facial paralysis is a simple type of dysphagia. Strokes may both alter the passage of food through pharynx and impair closure of the larynx. Aspiration pneumonia in post-stroke or post-cardiac surgery patients is a significant cause of increased hospitalization and potentially death.
In the final phase of swallowing, neurogenic disorders such as amyotrophic lateral sclerosis (Lou Gehrig's disease) impair peristalsis (movement of food down the esophagus); whereas, tumors and strictures obstruct the passage of food through the esophagus.
What are FEES and VFSS?
Swallowing is divided into three phases:
- The oral phase (mouth phase)
- Saliva moisturizes food
- Mastication (food chewed into smaller pieces)
- Funneling food to the back of the oral cavity (mouth)
- Directing the food into the pharynx (throat)
- The pharyngeal phase
- Closure of the upper pharynx (nasopharynx) by the soft palate o Movement of the food bolus by the pharyngeal muscles toward the esophagus
- Protection of the airway by the vocal folds
- Elevation of the larynx beneath the tongue and funneling the food past the larynx by the epiglottis (a cartilage directly above the vocal cords that closes over the larynx like a lid on a flip-up trash can)
- Food enters the esophagus
- The esophageal phase
- The food bolus enters the upper esophageus, propelled by the involuntary muscles of the esophagus to the stomach — this process is known as peristalsis and is the means by which food is directed through the entire digestive tract.
How is human swallowing different from lower animals and why is this Important?
Fiberoptic Endoscopic Evaluation of Swallowing (FEES)
FEES consists of passing a flexible fiberoptic endoscope through the nose to directly observe the palate, base of tongue, pharyngeal constrictors (muscles surrounding the throat) and larynx during swallowing.
Videofluoroscopic Swallowing Study (VFSS)
VFSS is a non-invasive study that is performed in radiology with a speech-language pathologist and a radiologist. Patients are asked to swallow a solution containing barium (a metallic compound) of various thicknesses while fluoroscopy permits observing the progress of the barium through the various swallowing phases.
In impaired individuals, the benefits of various maneuvers to compensate for dysphagia (trouble swallowing), such as head turning or chin tuck, can be observed, and the speech pathologist can make recommendations for dysphagia therapy and the proper texture of diet.
Why do aged and informed individuals suffer the most from swallowing disorders?
Lower animals and human infants are able to swallow and breathe at the same time. This is possible because the soft palate approximates the epiglottis and food is directed away from the larynx during swallowing, while air passes directly from the nose into the larynx. Over the subsequent three to six months of life, the human larynx descends and disconnection of the nasal airway from the oral cavity stops.
This descent lengthens the pharynx, permitting a wider range of vocalizations which may or may not have evolved to favor human language. However, such evolution makes humans more liable than other animals to inhale food into the windpipe, a condition called aspiration.
The complex coordination and timing of the upper digestive tract muscles makes them particularly vulnerable to aging. Further, neurogenic disorders may alter the control of muscles. These symptoms might first appear as impaired swallowing.