Monday, March 17, 2014

Sam Meredith McCoy Ch. 8


What is the total at rest length of the vocal folds for women? For men? 18 millimeters for women, 23 millimeters for men
What is the average length of the vibrating portion of the vocal folds? 12-15 millimeters                 
Why do we call them vocal folds instead of vocal cords? The term vocal folds more accurately describes their physiological characteristics i.e. that they are small folds of tissue located in the larynx.
What are the vocal folds? Small 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? Like two pearly white bands
What is the thin layer of skin cells on the VFs called? What do these 3 terms mean? The stratified (layers that become larger near the bottom) squamos (having layers that interlock like paving stones) epithelium (skin cells)
This area has another name.  What is it and why is it called this? the mucosa of the vocal folds because it 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 rest of the epithelium in the vocal tract is considered columnar epithelium, which has a different structure that stratified squamos epithelium
What makes up the body of the vocal folds? the thyroarytenoid muscle
What is the transitional layer called?  Describe it. the lamina propria: it lies between the body and the epithelium and is made up of three distinct regions whose different characteristics are a result of different distributions of collagen and elastin fibers
How is the structure of the vocal folds like both the back and the palm of your hand? The skin on the vocal folds is relatively free to move even though it is attached to the flesh beneath it, like the flesh on the back of the hand. The flesh on the palm of the hand offers padding, which absorbs shock. This role is played at a laryngeal level by the lamina propria.
Describe the steps of a single cycle of vibration according to the Myoelastic-Aerodynamic Model. 1) the vocal folds 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 continue 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 vocal fold 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 being spoken or sung
What is vertical phase difference?  Why is this important to vocal sound? glottal opening and closure always occurs with the lower edge preceding the upper edge; this is a major factor in the creation of the mucosal wave
Are aerodynamic factors sufficient to maintain vocal fold oscillation? No
Describe the steps of VF oscillation according to the one-mass model. 1) the glottis is initially closed by the 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 and elasticity/inertia of the vocal folds 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 allows vocal fold oscillation to continue for as many times per second as the fundamental frequency of the pitch that is spoken or sung
Describe the improvements in understanding VF oscillation because of the 3-mass model. it offers an explanation for the asymmetrical opening of the glottis by describing the vocal folds as three interconnected masses
What is the neurochronaxic theory?  If it valid? The theory that the vocal folds need nothing more than stimulation from the brain in order to vibrate. This theory has been discredited scientifically, but some singers still base their technique off of it..
Name the 5 cartilages that form the basic laryngeal framework. thyroid, cricoid, arytenoids, epiglottis, trachea
Name and describe the membranes and ligaments found within the larynx. thyrohyoid: located between the thyroid and the hyoid; its purpose is to link the two structures and prevent excess movement, cricothyroid: located in anterior space between cricoid and thyroid; their function is similar to that of the thyrohyoid membrane
Describe the aryepiglottic fold.  What is its alternate name? What is its function? It is a fold at the top of the larynx (it is also called the laryngeal collar or the epilarynx) whose function is to help pull the epiglottis down to cover the airway for swallowing. It also plays an important role in vocal fold resonance.
What is the purpose of the vocal ligament? to add strength to the medial edges of the vocal folds and limit the extent to which they can be stretched
What is the function of the aryepiglottic and the thyroepiglottic muscles for singing? They have no function for singing other than that they are sometimes used for enhancement of the singer's formant
What is phonation threshold pressure (PTP)? 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. Glottal onset: adduction precedes breath energy, aspirate onset: adduction occurs after breath flow, balanced onset: adduction and airflow begin at the same time
What is flow phonation? when there is a perfect union of airflow and adductory tension.
What happens if we increase breath pressure with constant adductory tension? the sound will get slightly louder, but will risein pitch and has the potential to become aspirate
 What happens is you increase glottal resistance at the same time as you increase breath pressure? the increase in intensity remains without change in intonation
As amplitude increases, how does this affect the glottis? it closes more quickly with each cycle of vibration                   
What happens to help this situation? there is a firmer cessation of airflow, which increases the amplitude of the sound wave
How do we increase vocal fold thickness, and what affect does this have on the sound? through contraction of the TA; it widens the contact area between the two vocal folds and increases the vocal fold mass that is in oscillation 
What is the typical dynamic range for dramatic voices?  What was maximum amplitude for these singers? 60-64 dB, 120 dB
How does the dynamic range and maximum amplitude of lighter voiced singers compare? the dynamic range is essentially the same, but the maximum amplitude is lower
How do pitch and amplitude relate to each other? Increase in pitch frequency requires longer, narrower vocal folds, whereas increased amplitude requires thicker vocal folds
How is the time that the glottis remains open impacted by adduction and pressure changes? as pressure increases the amount of time the glottis is open decreases
What is the estimated times of the various phases in q quiet tone vs a louder tone? 50% of the time in a quiet tone, 33% for a loud tone
What is the open quotient? the amount of time in vocal fold oscillation in which the glottis is open
How does the open quotient relate to amplitude? amplitude increases as the open quotient decreases
Why is it wrong to just blow harder to get louder? doing so can cause change in intonation
In very general terms, what must the vocal folds do to change pitch? they must be longer, stiffer and narrower
How does the body/cover model affect pitch change? The cover oscillates more independently on higher pitches.
How do pitch and intensity overlap in terms of vocal fold function? Higher pitches require longer, stiffer and narrower vocal folds, but louder sounds require thicker vocal folds 
How do the CT and TA work together to control pitch and amplitude? the CT pull the folds to the appropriate tension for pitch and the TA muscles provide 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 pressure than low pitches; increased pressure increases frequencies
Describe the inferior pharyngeal constrictor muscles connection to the larynx. Describe its function. they wrap around the entire vocal tract and provide a downward thrust for swallowing.
What is ossification? the gradual transformation of cartilage to bone
What is the downside of the flexibility of the thyroid cartilage in young people. it can lead to vocal instability and unpredictability
Describe the actions of swallowing the pharynx narrows, the larynx is raised, the epiglottis covers the glottis, the soft palate is lifted, the tongue elevates and retracts
Describe the pharyngeal constrictor muscles. the superior constrictor wraps around the top of the vocal tract, the middle constrictor attaches to the hyoid bone and stylohyoid ligament, the inferior constrictor lies at the bottom and attaches to the thyroid laminae
What doe gola aperta mean? an open throat
How do we open the throat? we relax the muscles that close the throat
What are the two ways in which laryngeal elevation can occur? it can be lifted directly through an attachment to the thyroid or cricoid cartilage or it can be lifted indirectly through the hyoid bone
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 thyrohyoid muscles whose function is to close the gap between the larynx and hyoid
Which muscles are indirect laryngeal elevators? the digastric muscle, the stylohyoid, the mylohyoid, the geniohyoid
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 digastric lowers the jaw still, but also raises the larynx
Which muscles can both depress the jaw and raise the larynx? mylohyoid and geniohyoid
Which muscles are laryngeal depressors? sternothyroid muscles, sternohyoid muscles, the omohyoid muscles
What is the ideal laryngeal position for classical singing? slightly below the natural resting place
How does the vertical position of the larynx change as we age? Be specific. when we are born the larynx is very high, but by age five it is usually around the fifth cervical vertebra. The larynx lowers further upon puberty and there is some additional lowering throughout adulthood
What is tracheal pull (tug)? the slight descent of the larynx caused by the contraction of the diaphragm
Which nerves serve the larynx? the vagus nerve, the superior laryngeal nerve, the rucurrent laryngeal nerve

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