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The primary structure of the phonatory system is the
Larynx.
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“Larynx” is pronounced
“la-rinks” NOT “lar-nicks”
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The phonatory system, like the respiratory system, serves an “overlaid” function for speech. The primary purpose of the structures of the phonatory system is to
protect the airway (keep things out of the lungs).
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when the vocal folds are “locked,” the larynx serves as a
“pressure device” when we are lifting heavy objects, coughing, sneezing, etc.
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When the folds are locked, they are closed tightly, so that there is no air flowing in and out of the lungs. This “fixes” the rib cage so that it does not move.
When the rib cage is fixed, it provides a rigid framework for the muscles that attach to it (including the accessory muscles of respiration).
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For speech purposes, the larynx takes the energy provided by the respiratory system and
converts it into a sound source.
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The larynx also controls
pitch and loudness of the voice
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The larynx sits on top
of the trachea.
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The larynx is made up largely of
Cartilage.
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The larynx provides a framework for a number of
muscles of phonation
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The Framework of the Larynx
- The major cartilages of the larynx are:
- (the epiglottis may also be considered as a laryngeal cartilage, but it is probably not important for phonation)
- the thyroid
- the arytenoids
- the cricoid : CAT
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The Cricoid Cartilage is described as “signet-ring shaped.” It is thin in the front, then rises up and becomes larger in back.
- It sits on top of the
- trachea.
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Unlike the C-Shaped “rings” of cartilage in the trachea, the cricoid
truly is a complete ring of cartilage.
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The Thyroid Cartilage is commonly referred as the
“Adam’s Apple” and it is the largest of laryngeal cartilages
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Landmarks of the Thyroid Cartilage. The two sides of the cartilage are
- known as the
- thyroid lamina
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The thyroid lamina come together to form
the thyroid angle. (The reason males’ Adam’s Apples protrude more than females’ is because the thyroid angle is different in males vs. females.)
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At the top of the thyroid angle is the
thyroid notch (you can feel this)
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The portions of the Thyroid Cartilage that protrude up and down are known as the
horns or cornu. (A good way to remember that the word cornu refers to horn is to think of a unicorn — a mythical one-horned animal)
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The superior horns connect with the
hyoid bone (which we’ll talk about shortly)
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The inferior horns connect with
the cricoid cartilage
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The arytenoid cartilages are
paired, pyramid-shaped cartilages
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The arytenoids sit atop the posterior portion of the
cricoid
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The orientation of the arytenoids on the cricoid allows them to
move in a variety of ways
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Since the vocal folds attach to the arytenoids, this flexibility in arytenoids’ movement is
important for vocal fold movement
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The arytenoids can rock on the cricoid... ...this is a
front-to-back movement of the arytenoids
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The arytenoids can glide on the cricoid... this is a
side-to-side movement of the arytenoids
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The arytenoids can rotate on the cricoid...this is a
pivoting movement of the arytenoids
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The rocking, gliding, and rotation of the arytenoids can be combined, so that the arytenoids have
considerable flexibility of movement
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The portion of the arytenoids that protrudes to the front
is called the vocal process
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The portion of the arytenoids that protrudes to the side is called
The muscular process
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The portion of the arytenoids that protrudes to the top is called
The apex
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On top of the apex is a small cartilage known as
the corniculate
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The epiglottis is a “leaflike” piece of cartilage that attaches
inside the thyroid angle, below the thyroid notch
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The epiglottis is not important for phonation, but does serve a function
during swallowing. It moves backward during swallowing to help protect the airway
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Thyroid Cartilage
- Thyroid Notch Lamina
- Superior horn (cornu) Inferior Horn (cornu)
- Tracheal Rings (C-shaped cartilage)
- The trachea is not part of the larynx--the larynx sits on top of it
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Arytenoid Cartilages
Sit atop Cricoid
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Cricoid Cartilage
Signet-ring shape
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For our purposes, most important larygeal cartilages for speech are:
Cricoid and Thyroid and the Arytenoids
- The Intrinsic Laryngeal Muscles – the vocal folds (similar attachments)
- Interior thyroarytenoid muscles (vocalis)
- External thyroarytenoid muscles
- Vocal Ligament
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The internal thyroarytenoid muscles (vocalis) make up part of
the vocal folds
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The vocalis fibers arise from
from inside the thyroid cartilage, just beneath the thyroid notch, and attach to the vocal process of the arytenoid.
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When The internal thyroarytenoid muscles contracts:
it serves to shorten and stiffen the vocal folds
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The external thyroarytenoid muscles also make up part of
the vocal folds
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The external thyroarytenoid fibers also arise from inside the
thyroid cartilage, just beneath the thyroid notch and attach to the anterior portion of the muscular process of the arytenoid
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When the external thyroarytenoid muscle contracts, it serves
to shorten and adduct the vocal folds (bring them closer to midline)
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To “adduct” means to
bring the vocal folds toward midline (in other words, close the folds) Think of ADDuct: you “add the folds together”
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To “abduct” means to
- move the vocal folds away from midline (in other words, open the folds)
- Think of an abduction: you “take someone away”
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The glottis is the
opening between the vocal folds. (Strictly speaking, when the folds are fully adducted, we have no glottis)
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In addition to the internal thyroarytenoid (vocalis) and external thyroarytenoid muscles, there is one additional structure that makes up the vocal folds.....
this is the vocal ligament
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The vocal ligament runs from the
- vocal process of the arytenoids to just below the thyroid notch
- It is the most medial portion of the vocal folds
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As its name suggests, the cricothyroid muscles go
from the upper border of the cricoid cartilage to the lower border of the thyroid cartilage.
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The cricothyroid muscles have two portions...
- ...the pars recta (with fibers that have a vertical orientation)...
- ...and the pars oblique (with fibers that are somewhat angled)
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Both of the pars recta and pars oblique serve to
lengthen the vocal folds; the pars recta by rocking the thyroid cartilage forward and the pars oblique by pulling the thyroid cartilage forward
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via action of the Cricothyroid Muscles (pars recta fibers)
- As the cricothyroid contracts, it rocks the thyroid forward...
- ...this increases the distance between the vocal processes of the arytenoids and the thyroid notch, thus lengthening the vocal folds
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The Posterior Cricoarytenoid Muscle goes from
the back of the cricoid cartilage and attaches to the muscular process of the arytenoid
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When The Posterior Cricoarytenoid Muscle contracts,
it pulls back on the muscular process causing the arytenoids to rotate... ...and therefore the vocal processes move away from midline... ...this results in abduction of the vocal folds.
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When the posterior cricoarytenoid muscle contracts, it pulls back on the
muscular process.....this causes the arytenoids to rotate and therefore the vocal processes move away from midline, this results in abduction of the vocal folds.
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The lateral cricoarytenoid muscle goes from the side of
the cricoid cartilage to the muscular process of the arytenoid
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When the lateral cricoarytenoid muscle contracts:
- it pulls forward on the muscular process(es) of the arytenoid(s), which causes the arytenoids to rotate, thus moving the vocal processes toward midline, which results in adduction of the vocal folds.
- The “Interarytenoid” Muscles are the
- Transverse Arytenoid and Oblique Arytenoid
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Transverse Arytenoid and Oblique Arytenoid are located
between the two arytenoid cartilages
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The transverse arytenoid fibers run
horizontally between the two arytenoids
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The oblique arytenoid fibers run
from the base of one arytenoid to the apex of the other
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Both Transverse Arytenoid and Oblique Arytenoid serve to
pull the arytenoids closer together, thus bringing the vocal processes toward midline, resulting in adduction of the vocal folds.
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The supraglottal cavity is an area just above
the vocal folds.
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The supraglottal cavity is formed by
- The epiglottis in front
- Arytenoids in the back
- And the aryepiglottic folds on the side
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The aryepiglottic folds are formed by the
aryepiglottic muscle
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Within the aryepiglottic folds are the
aryepiglottic muscles
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the aryepiglottic muscles extend from
- the (apex of the) arytenoid cartilage up to the side of the
- epiglottis, they serve to lower the epiglottis
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aryepiglottic muscles may be considered a continuation of
- the oblique arytenoid muscle because it begins at the muscular process of one arytenoid, crosses over at the apex, and extends up to the epiglottis
- The muscle that serves to elevate the epiglottis is the
- thyroepiglottic muscle.
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thyroepiglottic muscle extends from inside the
thyroid cartilage to the epiglottis
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The aryepiglottic muscle and thyroepiglottic muscle work as
an agonist-antagonist pair
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Laryngeal Membranes and Ligaments
- Located above the true vocal folds are the false vocal folds...
- ...unlike the true folds . . .
- the false vocal folds are nonmuscular structures, and they do not vibrate like the true folds
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If the false and true folds do vibrate, it is a condition known as
Diplophonia.
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Individuals with a hyperadductive vocal mechanism may also force . . . the false folds together
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The space between the true and false folds is the
Laryngeal Ventricle or the Ventricle of Morgagni
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Extending from the vocal ligament to the cricoid cartilage is the:
conus elasticus
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Extrinsic Laryngeal Muscles
- The Hyoid Bone is an important structure to consider as we discuss the extrinsic laryngeal muscles. The hyoid is a small, . . .
- unpaired bone that is located above the larynx
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The tongue “sits” on the
hyoid, so the hyoid is considered by some to be a bone of the skull
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Between the thyroid cartilage and the hyoid bone is the (well-named)
thyrohyoid membrane
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Extrinsic Laryngeal Muscles: Suprahyoid Muscles
- (As the name suggests, these muscles are located
- above the hyoid bone)
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The mylohyoid muscle extends
from the inside of the lower jaw (genu) to the hyoid bone
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The geniohyoid muscle extends from the
- middle inside of the lower jaw to the hyoid bone
- (“Genu” refers to a “knee” or “bending”—think of “genuflect”)
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Extrinsic Laryngeal Muscles: Suprahyoid Muscles
- The digastric muscle has two “bellies” that meet at an
- intermediate tendon located at the hyoid bone
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The anterior belly of the digastric goes from the
inside of the lower jaw to the intermediate tendon, while the posterior belly of the digastric goes from the mastoid process of the skull to the intermediate tendon
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Extrinsic Laryngeal Muscles: Suprahyoid Muscles The stylohyoid muscle goes from the
- styloid process of the skull to the hyoid bone;
- they can serve to “fix” the hyoid bone in place so that the thyrohyoid muscle can elevate the larynx.
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Extrinsic Laryngeal Muscles: Infrahyoid Muscles
- (As the name suggests, these muscles are located
- below the hyoid bone)
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The thyrohyoid muscle, as its name suggests, goes from the
- thyroid cartilage of the larynx to the hyoid bone.
- When this muscle contracts, it elevates the larynx
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The sternothyroid muscle goes from the
- sternum to the thyroid cartilage. When this muscle contracts, it lowers (or depresses) the larynx
- Elevation of the larynx leads to an increase in pitch, while lowering the larynx leads to a
- decrease in pitch
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Physiology of the Larynx for Nonspeech Activities
- 1. Recall that the larynx can serve as a “pressure device.” When used in this way, we forcefully adduct our vocal folds to prevent air from escaping from the lungs.
- 2. When breathing for life purposes, we slightly abduct our vocal folds so that air can flow into and out of the lungs
- 3. When we need more air (e.g., during strenuous activity), we abduct our vocal folds more so that more air can flow into and out of the lungs
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Physiology of Phonation
- When we speak, most of the laryngeal adjustments we make are not as simple as fixing the hyoid bone and elevating the larynx. There are a number of rapid, complex adjustments taking place as we phonate.
- When we prepare to phonate, we adduct our folds so that the air from the lungs can cause them to vibrate
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Physiology of Phonation
- When we whisper, we adduct our vocal folds more than when we phonate. This results in a “whisper triangle”
- We also move the posterior portion of the arytenoids apart and move the vocal processes of the arytenoids close together..The “whisper triangle” is a constriction through which air flows in a turbulent fashion, providing the sound source for a whisper
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Physiology of Phonation—The Glottal Cycle
- A glottal cycle is one vibratory cycle of the vocal folds.
- The cycle (usually) begins with the folds adducted... air pressure begins to build beneath the folds...the folds begin to “blow apart” from bottom to top...the folds open and air flows between them...the folds come back together...and the cycle begins again.
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Physiology of Phonation—The Glottal Waveform
If we were to measure the airflow between the vocal folds as they vibrate, we would get a display that looks something like a wave. This is known as the glottal waveform (one wave is one vibratory cycle of the vocal folds)
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Since airflow through the glottis is related to the amount of glottal opening, The Glottal Waveform can also represent the opening and closing of the vocal folds
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Physiology of Phonation—The Glottal Cycle
- Let’s examine one cycle:
- Airflow v. time
- Note that the vocal folds take more time to open.....than they do to close, thus the “wave shape”, because the glottal cycle is influenced by both the elastic characteristics of the muscles and by the aerodynamics of air flowing between the vocal folds
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Physiology of Phonation—The Glottal Cycle
As subglottal pressure builds up under the vocal folds, they blow apart, as the folds reach their maximum opening, the elastic characteristics of the muscles cause them to begin to move back toward midline, in addition, the air flow between the folds causes a suction known as the Bernoulli effect, which “snaps” the folds back together; and that’s why there is a shorter closing duration in the cycle
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Physiology of Phonation—The Glottal Cycle are fairly consistent in the
- Vibratory patterns of our vocal folds from cycle to cycle...
- ...that is, one cycle is quite similar to the next in terms of its frequency and amplitude
- A certain amount of variability from cycle-to-cycle is normal
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Jitter and Shimmer
- When the glottal cycles vary in their frequency from cycle to cycle...
- we have a condition known as frequency perturbation commonly referred to as jitter
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Jitter and Shimmer
- When the glottal cycles vary in their amplitude from cycle to cycle...
- we have a condition known as amplitude perturbation... ...commonly referred to as shimmer
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Instrumentation and Voice: We have a number of ways to measure the function of the vocal mechanism:
- We can, for example, visually examine the mechanism using:
- direct laryngoscopy, indirect laryngoscopy,
- fiberscopic techniques: Rigid fiberscope, Flexible fiberscope
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We can measure the acoustic signal and use electronic
- and computer-based means to determine
- vocal fold vibratory patterns
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We can use an electroglottograph to measure
vocal fold contact area, which gives us an indirect assessment of vocal fold function
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Parameters of Voice
- The voice can be described in a number of ways.
- register, pitch, loudness, and quality
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Parameters of Voice -- There is some controversy about vocal register
- – Falsetto (light register)
- – Head register (upper modal)
- – Modal (chest register) – Used in speech
- – Vocal fry (pulse register)
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Parameters of Voice • Pitch –
- Described in terms of fundamental frequency
- – The number of times per second that the vocal folds vibrate =
- cycles/second = Hertz (Hz)
- – On average, males have a fundamental frequency of about 125 Hz,
- females have an average fundamental frequency of about 200-225 Hz
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Parameters of Voice • Loudness – The term “loudness” is self-explanatory – Affected both by respiratory and phonatory factors
- • We can increase loudness by increasing respiratory driving pressure • We can increase loudness by making phonatory adjustments, such as
- increasing glottal resistance
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Parameters of Voice • Quality
- – Vocal quality is difficult to quantify, tends to be a subjective measure – Breathiness
- • Affected by amount of air flowing between the vocal folds
- – Harshness
- • May relate to constriction of the vocal folds during phonation
- – Hoarseness
- • We’ve all experienced this
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