Page 66 - Fall2021

PHYSICS OF VOCAL HEALTH
Clinical Voice Care
Clinical voice care attempts to restore the voice through medical, behavioral, and/or surgical interventions. When the voice disorder is triggered by an underlying medical condition, such as vocal fold swelling due to an upper respiratory infection, reflux, or smoking, medical treat- ment is necessary to clear the medical condition. Due to the delicate structure of the vocal folds, particularly within the membranous cover layer, the initial treat- ment is often behavioral or voice therapy, particularly for nonorganic voice disorders but also for some organic voice disorders such as vocal fold nodules (Figure 2). The goal of voice therapy is to restore the best voice possible, something that is often achieved through vocal health education and modification of vocal behavior using dif- ferent vocal techniques and exercises. Even for patients who eventually require surgery, pre- and postoperative voice therapy is essential to achieve an optimal voice out- come and prevent recurrence of the voice disorder. For organic voice disorders or conditions of glottic insuffi- ciency, surgical intervention is often more effective.
One of the most common voice disorders in the clinic is muscle tension dysphonia. It involves too extensive an effort in producing the voice, with excessive muscle force and a tight larynx configuration. Some patients may also present with vocal fold lesions such as nodules, due to the chronic exposure to excessively high vocal fold contact pressure. Voice therapy is often effective in improving voice in these patients. For example, external circum- laryngeal massage is often used to relax the larynx in patients with notable tension in the musculature around the neck. Some techniques take advantage of tasks such as yawning or sighing that are naturally produced with a reduced laryngeal muscle tension and a less adducted glottal configuration, often with a lowered vertical position of the larynx. By starting with such tasks and gradually transitioning into speech, the speaker can be trained to produce voice with the same relaxed laryngeal configuration, thus reducing vocal fold contact pressure and the risk of vocal fold injury.
Various vocal exercises are also used to train speakers to produce voice with a focus on vibratory sensations around the lips and cheek and along the alveolar ridge of the palate (e.g., resonant voice therapy), thus avoid- ing a tight sensation at the larynx. In some exercises, the speaker is instructed to perform pitch or loudness glides
with a semi-occluded vocal tract configuration, produc- ing either nasal sounds, trills, or phonating into a narrow tube such as a drinking straw. It is generally believed that by focusing on vibratory sensations in certain parts of the vocal tract, the speaker may adopt a vocal configuration that improves vocal efficiency and minimizes vocal fold contact pressure.
An important component of voice therapy is to reestab- lish the balance between respiration, phonation, and articulation. For example, for voice disorders resulting from weakened respiratory function or improper respira- tory behavior, voice therapy often focuses on respiration strength training to improve respiratory function or training the speaker to begin speaking at an appropriate lung volume to ensure sufficient air supply required for speech (Desjardins et al., 2021).
For vocal fold mass lesions that are large in size, such as vocal fold polyps, cysts, and sometimes even nodules, voice therapy may have little effect and surgical removal is necessary. Because the membranous cover layer of the vocal folds is the vibrating component, it is critical that surgery remove as little tissue as possible and avoid sig- nificantly altering the delicate structure and mechanical properties of the vocal fold cover layer. Vocal fold scar- ring after surgery, particularly on the vocal fold medial surface where vocal fold vibration modulates airflow most effectively, often negatively impacts the patient’s voice and vocal capabilities.
For patients who are unable to sufficiently adduct the vocal folds due to vocal fold paralysis, paresis, atrophy, or aging, vocal fold adduction can be improved through an office-based injection augmentation procedure in which fat or another material is injected into the vocal folds to displace the medial edge of the vocal folds toward the glottal midline. A more permanent solution is medial- ization laryngoplasty, in which an implant is inserted laterally to the vocal folds to permanently displace and reposition the vocal folds toward the glottal midline (Isshiki, 1989). These procedures are often able to sig- nificantly improve glottal closure and voice quality and reduce vocal effort.
In addition to adjusting the vocal fold position, vocal fold surgery also allows manipulation of vocal pitch. One way to achieve this is to adjust vocal fold tension
66 Acoustics Today • Fall 2021