Caitlin Craig McCoy Chapter 8

What is the total at rest length of the vocal folds for women? For men? 18 millimeters for women, and about 23 millimeters for men.

What is the average length of the vibrating portion of the vocal folds? 12-15 millimeters long for men and women.

Why do we call them vocal folds instead of vocal cords? It describes the physical characteristics of the tissue more accurate and precisely than cords do. 

What are the vocal folds? They are folds of tissue located in the anterior/posterior plane at the top of the airway. 

What do the vocal folds look like when viewed from above? They look like two pearly-white bands, and look like the letter V at rest. They come together closing at the posterior during phonation. The bottom of the V is where the Adam's apple is. 

What is the thin layer of skin cells on the VFs called? What do these 3 terms mean? The external layer, or cover consists of a thin layer of skin cells called the stratified squamous epithelium. Epithelium- several layers of skin cells, squamous- that interlock like paving stones, stratified- which progressively become larger toward the bottom layer. 

This area has another name.  What is it and why is it called this? The area is also referred to as the Muscosa of the VF's. This is because the area is constantly bathed in mucus. 

What is unique about this layer of skin (covering the VFs) as opposed to the rest of the epithelium of the vocal tract? The entire respiratory tract--from the lips to the bottom of the trachea--is lined with muscosa. This takes the form of stratified squamous epithelium only on the surface of the vf's and in some of the areas that lie immediately above them. The remainder consists of columnar epithelium (cells arranged in columns). Below the vf's, the columnar epithelium is ciliated. This region is covered with microscopic hairs that constantly transport mucus up the airway for disposal via the esophagus and stomach.

What makes up the body of the vocal folds? The body of the vf's consists of a muscle called the thryoartenoid, which takes its name from its points of origin (thyroid cartilage) and insertion (arytenoid cartilage). 

What is the transitional layer called?  Describe it. The lamina propria lies between the TA and the epithelial cover. It also subdivides into three distinct regions with different physical characteristics, which are caused by changes in the distribution of elastin and collagen fibers. The superficial (outermost) layer is coupled to the epithelium through a basement membrane. This is the thinnest layer and also has the lowest viscosity. (viscosity is a measure of fluid density. Water has low viscosity; pancake syrup has much higher viscosity.)

How is the structure of the vocal folds like both the back and the palm of your hand? Gently massage the back and palm of your hand. Notice that the skin on the palm is firmly attached to the flesh beneath it. As you massage the back of your hand, however, the skin is relatively free to move (somewhat like the skin of a kitten). Next, gently poke a finger against the palm and back of your hand; the palm offers much more padding than the back, acting somewhat like a shock absorber. Your VF's share both of these characteristics; the cover slips over the body like the skin on the back of your hand, while the lamina propria cushions blows like the palm of your hand. 

Describe the steps of a single cycle of vibration according to the Myoelastic-Aerodynamic Model.
1.The Vf's are gently closed by muscular forces within the larynx.
2. air pressure increases beneath the closed glottis.
3. increasing air pressure begins to open the glottis. Because of the ability of the cover to move independently of the body,this opening begins on the underside of the glottis.
4. The glottis continues to open, from bottom to top, until air begins to escape
5. as the air begins to flow through the glottis, its velocity increases and its pressure decreases, as explained by the Bernoulli Effect.
6. Elasticity of the VF acts somewhat like a spring, exerting a return force that begins to close the glottis; negative pressure caused by the Bernoulli Effect supplies additional closing force.
7. The glottis closes again, from bottom to top.
8. As soon as the glottis is fully closed, the process begins again, repeating as many times per second as the frequency of the pitch begin spoken or sung.

What is vertical phase difference?  Why is this important to vocal sound? Note the vertical phase difference between the lower and upper edges of the vf's throughout the oscillatory cycle. During phonation, glottal opening and closure always occurs in this manner with movement of the lower edge preceding the upper edge (at high pitch, the folds often are so thin that this phase difference no longer is significant). Independent movement of the inferior and superior portions of the vf's is a major factor in the creation of the muscosal wave; as the folds make contact at their lower edge, a wave begins to ripple across their surface, much like a wave traveling across the surface of a pond into which a pebble has been dropped.

Are aerodynamic factors sufficient to maintain vocal fold oscillation? No. 

Describe the steps of VF oscillation according to the one-mass model. 
1. As in the A-M Theory, the glottis initially is closed by muscles in the larynx
2. subglottal air pressure increases until it overcomes the muscular and tissue resistance and opens the glottis
3. reduced air pressure through the glottis (Bernoulli) and elasticity/inertia of the vf's brings the glottis back together, reducing the flow of air.
4. because of inertia, air above the glottis continues its forward motion in spite of reduced flow through the glottis, producing an area of low air pressure immediately above the glottis.
5. The combined forces of elastic recoil of the folds, the pressure drop through the glottis, and the low pressure region above the glottis complete the cycle, closing the glottis.
6. asymmetry of air pressure below and above the glottis (steps 1-5) allows vf oscillation to continue for as many times per second as Fo of the pitch that is spoken or sung. 

Describe the improvements in understanding VF oscillation because of the 3-mass model. Further improvements are made to oscillation theory by describing the vf's as three interconnected masses. In this model, the body of the vf (thyroarytenoid muscle) is the first and largest mass. The upper and lower portions of the cover (lamina propria and epithelium) comprise two smaller masses. In this model, the glottis opens and closes asymmetrically with vertical phase difference from bottom to top. Air pressure also is asymmetrical, increasing when the glottis is in a convergent shape (bottoms of the two folds are farther apart from each other), and decreasing when the glottis is divergent (tops of the two folds are farther apart). This asymmetry of air pressure provided by the three-mass model, combined with the impact of pressure changes above the glottis caused by inertia, is sufficient to sustain vf oscillation.

What is the neurochronaxic theory?  If it valid? Nerve impulses from the brain are the sole cause of vf vibration and that airflow only is neede to carry the sound outside the body. Even though this theory has been discredited scientifically, one still encounters a few singers who try to base their singing technique on it.

Name the 5 cartilages that form the basic laryngeal framework. Thyroid cartilage, cricoid, two artyenoid cartilages, and the epiglottis.

Name and describe the membranes and ligaments found within the larynx.
1. Thyrohyoid membrane is located in the area between the thyroid cartilage and the hyoid bone. Its purpose is to link the two structures, providing a seal and preventing excess movement. Two small holes are found toward the sides of this membrane through which pass one pair of the nerves that serve the larynx.
2. cricothryoid (membrane and ligament) is located in the anterior space between the cricoid and thyroid cartilages. Their function is similar to that of the thyrohyoid membrane. 
3. conus elasticus is a membrane that lines the inside of the cricoid cartilage. It strengthens the underside of the vf's and seals them to the airway below.

Describe the aryepiglottic fold.  What is its alternate name? What is its function? Aryepiglottic fold is found at the top of the larynx, which is alternately called the laryngeal collar or the epilarynx. This region is formed of muscle and tissue that encapsulates the epiglottis and arytenoids, helping to pull the epiglottis down to cover the airway for swallowing. The epilarynx also plays an important role in vocal resonance and is the probable source of the singer's formant. 

What is the purpose of the vocal ligament? vocal ligaments extend from the thyroid cartilage at the anterior commissure to insert into the arytenoid cartilages at the vocal processes. This ligament, which runs through the intermediate lamina propria, is made of filamentous strands resembling cotton fibers. Its purpose is to add strength to the medial edges of the vf's and to limit the extent to which they can be stretched.

What is the function of the aryepiglottic and the thyroepiglottic muscles for singing? They assist in swallowing, not phonation. The epiglottis must be pulled downward when swallowing, covering the glottis to prevent choking. This is the job of the aryepiglottic and thyroepiglottic muscles.

What is phonation threshold pressure (PTP)? PTP is the pressure required to overcome the resistance of glottal adduction and initiate vocal fold oscillation.

What are the 3 principle types of vocal onset? Describe how they differ in terms of the sequence of adduction and airflow.
1. Glottal onset occurs when strong adductions precedes breath energy. In this articulation, the glottis is squeezed tightly shut by the adductor muscles, after which subglottal pressure is increased until breath explodes through the glottis; strong glottal onsets resemble a grunt. Excessive use of these harsh onsets can lead to pathological voice problems, including vocal nodules. Gentle glottal onsets, however, should have no negative impact on the voice; indeed, if they did, virtually all speakers of German and English would have voice disorders. The key is degree. A successful glottal onset must have only enough adduction prior to phonation to produce the appropriate phoneme.
2. Aspirate onset occurs when adduction and breath flow occur in the reverse order; breath flow is started, and the vf's are slowly adducted into the moving air until the Bernoulli Effect enables oscillation to begin. Aspirate onsets are usually marked by a distinct /h/ that precedes each utterance. Like the glottal extreme, excessive use of strong aspirate onset can lead to voice problems, including chronic incomplete glottal closure and muscular tension dysphonia.
3. Balanced onset is one in which adduction and airflow begin at precisely the same instant, the resulting sound is clean and easy, without the strong click of the glottal stroke or the hissing of the aspirate. Singers can practice balanced tonal onset using exercises that require a gentle re-articulation of repeated notes.

What is flow phonation? For optimal production of sustained tones, a perfect union of airflow and adductory tension is required. When this occurs, the tone is described as balanced. Some voice scientists, refer to this as flow mode phonation. 

What happens if we increase breath pressure with constant adductory tension? The sound will probably get slightly louder, but it will also rise in pitch and has the potential to become aspirate from excess airflow. 

 What happens is you increase glottal resistance at the same time as you increase breath pressure? It would cause the vf's to oscillate at higher amplitude (greater range of motion) and to close more quickly during each cycle of vibration. 

As amplitude increases, how does this affect the glottis? What happens to help this situation? As closing velocity within the vibratory cycle increases, the ratio of time the glottis is closed--the closed quotient--also is likely to increase. The result is a crisper, firmer cessation of airflow that increases the amplitude of the soundwave.
How do we increase vocal fold thickness, and what affect does this have on the sound? Cindy told me not to answer this.

What is the typical dynamic range for dramatic voices?  What was maximum amplitude for these singers? Range- 60-64dB with a maximum amplitude exceeding 120dB.

How does the dynamic range and maximum amplitude of lighter voiced singers compare? Similar range overall, but with a lower absolute maximum.

How do pitch and amplitude relate to each other? Loudness steadily rises in response to higher pitch.

How is the time that the glottis remains open impacted by adduction and pressure changes? As adduction and pressure increase, the length of time the glottis remains open becomes progressively shorter. 

What is the estimated times of the various phases in q quiet tone vs a louder tone? During quiet phonation, the folds are in their opening phase for 50% of each cycle, in the closing phase for 37%, and are completely closed for 13%.
In louder phonation, the opening phase may diminish to 33%, while the closing phase remains at 37%, and the closed phase jumps to 30%. 

What is the open quotient? Open quotient represents the time the glottis is open during each cycle; a measurement of 0 indicates the glottis never opens, a measurement of 1 indicates the glottis never fully closes. 

How does the open quotient relate to amplitude? Amplitude was found to steadily increase as the open quotient fell from 1.0, reaching its peak somewhere between 0.5 and 0.6 (at an open quotient of 0.5, the open and closed phases are equal).

Why is it wrong to just blow harder to get louder? Singers would simply "blow harder" to increase volume are very likely to sing sharp. The correct balance between laryngeal tension and breath pressure must be found. Unfortunately, we are neither able to sense nor directly control adductory tension within the larynx.

In very general terms, what must the vocal folds do to change pitch? the vf's must be elongated for pitch to descend, and shortened to ascend. 

How does the body/cover model affect pitch change? At lower frequencies, the entire fold tends to oscillate. As pitch ascends, however, the body and cover become more independent, and for the highest pitches, the vf's might thin to the point where only there very leading edge of the cover is in oscillation. 

How do pitch and intensity overlap in terms of vocal fold function? Pitch and intensity control overlap at this point. Higher pitches require longer, stiffer and narrower vf's, but louder sounds require thicker vf's that offer more resistance to glottal airflow. 
How do the CT and TA work together to control pitch and amplitude? The CT muscles pull the folds to the appropriate tension for a given pitch, while the TA muscles counter with appropriate tension for the given amplitude. 

Describe how variations in air pressure have different impacts on low vs. high frequencies. High pitches tend to require more subglottal air pressure than low pitches. Some questions remain, however, as to cause and effect. We know that stiffening the vf's increases fundamental frequency. One of the by-products of this increased rigidity is the need for greater air pressure to overcome glottal resistance and establish vf oscillation. Simply increasing air pressure also can raise fundamental frequency. This should come as no surprise to singers who are experienced in controlling flatting through careful attention to breath support. 

Describe the inferior pharyngeal constrictor muscles connection to the larynx. Describe its function.
1. Inferior constrictor is the lowest of the three. It attaches to either side of the thyroid cartilage and wraps around the vocal tract and the base of the esophagus; contraction narrows the pharynx and elevates the larynx. But there is a possible side effect of its contraction, especially in younger singers whose laryngeal cartilages have not yet begun to ossify.
What is ossification? Ossification is the gradual transformation of cartilage to bone. 

What is the downside of the flexibility of the thyroid cartilage in young people. This flexibility in young people often leads to vocal instability and unpredictability. Ossification, which is well underway by early adulthood, greatly reduces this flexibility and leads to a more stable, predictable tone. In a pre-ossified larynx, contraction of the inferior constrictor might squeeze the sides of the thyroid slightly closer together, thereby elongating the entire cartilage in the anterior/posterior plane. This elongation stretches the vf's, effectively "lending a hand" to the cricothyroids to create higher pitches. When the cartilage ossifies, the inferior constrictor no longer can help stretch the vf's. 

Describe the actions of swallowing. As you swallow the larynx sharply ascends. This helps fold the epiglottis over the airway to prevent choking, while simultaneously directing whatever is being swallowed into the top of the esophagus. Neither of these actions works properly if the laryns does not rise. Several other things also must occur when you swallow. First the soft palate is lifted, closing off the nasal port, so foreign matter isn't pushed up into the nose. Simultaneously, your tongue elevates and retracts, pushing food into the throat, while the walls of the pharynx constrict to assist in the process. At the conclusion of the swallow, the larynx lowers and the epiglottis returns to its resting position.

Describe the pharyngeal constrictor muscles. 
1. The superior constrictor wraps around the top of the vocal tract in the region of the naso- and oropharynx, attaching to the skull and mandible. 
2. The middle constrictor attaches to the hyoid bone and the stylohyoid ligament. This ligament runs from hyoid to the styloid process of the skull
3. The inferior constrictor lies at the bottom of this muscle complex, attaching to the thyroid laminae (sides of the cartilage between the two horns) as well as the cricoid cartilage. Functionally, the upper two constrictors primarily serve to narrow the pharynx, assisting in the transport of food to the esophagus, while the inferior muscle constricts the pharynx and lifts the larynx.

What doe gola aperta mean? Open throat. 

How do we open the throat? The soft palate can be elevated by several millimeters to increase vertical space, possibly providing sensations of an open throat in the process. But the remainder of the vocal tract, including the naso-, oro-, and laryngopharynx, only can be tensed or relaxed. This is perhaps one of pedagogic situations in which "doing nothing" actually feels like "doing something". Maximum opening of the throat occurs when all tension is released from the three sets of constrictor muscles. The sensation is one of the active opening; the cause, however, is passive relaxation.

What are the two ways in which laryngeal elevation can occur? It is lifted directly through an attachment to the thyroid or cricoid cartilage, or it is lifted indirectly through the hyoid bone, which is connected to the larynx, tongue, and jaw. 

Which structures is the hyoid connected to? The larynx, tongue, and jaw.

Besides the inferior pharyngeal constrictor, what is the other true laryngeal elevator? Describe its function. The thyroid muscles, which arise from the inferior edges of the thyroid cartilage and insert into the hyoid bone. One would expect this muscle to act by pulling the hyoid bone toward the thyroid cartilage, thereby depressing the larynx. This is not, however, the normal action of the muscle, which lifts the larynx and partially closes the gap between the thyroid cartilage and hyoid. Excess tension in this muscle is a common factor in the vocal health problem known as muscular tension dysphonia, which often is a precursor to more serious pathologies. 

Which muscles are indirect laryngeal elevators?
1.The paired digastric is an example of a dual-purpose muscle, serving to raise the larynx and/or lower the jaw. Unfortunately, this muscle is very adept at performing these two functions simultaneously. Each digastric has two independent bellies; the anterior digastric originates at the hyoid bone and the inserts to the mandible near the center point, while the posterior digastric originates at the mastoid process of the skull and inserts to the hyoid. Contraction of the anterior portion of this muscle induces jaw depression; the posterior portion lifts the hyoid and larynx during swallowing. 
2. The stylohyoid muscles
3. The mylohyoid muscles

If the muscles that close the jaw (masseter, temporalis, medial pterygoid) fail to release when the jaw is opened, what if the effect of the contraction of the anterior belly of the digastric? The jaw becomes rigidly fixed in place. In this situation, contraction in the anterior digastric still lowers the jaw, but also elevates the larynx. 

Which muscles can both depress the jaw and raise the larynx? The mylohyoid muscles.

Which muscles are laryngeal depressors? The sternothryoid muscles, sternohyoid muscles, and the omohyoid muscles.

What is the ideal laryngeal position for classical singing? The ideal laryngeal singing posture is one that allows the larynx to remain at or very slightly below its natural resting place.

How does the vertical position of the larynx change as we age? Be specific. At birth, the base of the cricoid is located at the level of the third cervical vertebra. By age 5, it has already descended to C5. Puberty induces the next big change, lowering the larynx to C7, with some additional lowering continuing throughout adulthood.

What is tracheal pull (tug)? It is a phenomenon which occurs when the descending diaphragm pulls down the lungs, bronchial tubes, trachea, and larynx. 

Which nerves serve the larynx? Two nerves serve the larynx, both of which are branches of the vagus nerve, also called the 10th cranial nerve. The vagus leaves the brain and skull through the same opening provided for the jugular vein. It then takes a wandering path through the neck, into the thorax and upper part of the abdomen. The superior laryngeal nerve leaves the vagus from a position in the neck just above the larynx and also generates the tickle sensation that precedes a cough. The external superior is a motor nerve that supplies the cricothyroid muscle and therefore helps to control ascending pitch. The recurrent laryngeal nerve, a motor nerve that departs the vagus from a position well below the larynx in the upper region of the thorax, supplies all the remaining laryngeal muscles.