II' The Phonatory System:

1
II. The Phonatory System
2
A. Structures of the Phonatory Tract

• The phonatory tract is the pathway a sound takes
  from the moment it is produced until it leaves a
  persons head.
• The four regions of the vocal tract are the
  nasal, the oral, the laryngeal, and the
  pharyngeal cavities.
• For this module, we will focus on the pharyngeal
  and laryngeal regions.

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1. The Pharynx

• The pharynx is a musculo-membranous tube lined
  entirely with mucous membrane.
• It is 4-5 long and somewhat oval in shape.
• It extends from the base of the skull to in
  between C6 and the cricoid cartilage of the
  larynx.

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1. The Pharynx

• The pharynx is divided into three parts
• the nasopharynx,
• the oropharynx and the
• laryngopharynx.

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a. The Nasopharynx

• The nasopharynx is the uppermost portion of the
  pharynx.
• Its superior boundary is the base of the skull.
• Its anterior boundary is the nasal cavity.
• Its inferior boundary is the soft palate.

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a. The Nasopharynx

• The lateral walls of the nasopharynx contain the
  pharyngeal orifice, the opening into the
  Eustachian tube.
• This opening allows communication with the middle
  ear.

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a. The Nasopharynx

• The posterior nasal port can be opened or closed
  depending on the position of the soft palate.

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b. The Oropharynx

• The oropharynx begins superiorly at the soft
  palate.
• It extends inferiorly to the hyoid bonea bone
  running roughly parallel to the chin at the base
  of the tongue.

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b. The Oropharynx

• Anteriorly, the oropharynx communicates with the
  faucial pillars of the oral cavity.
• The palatine tonsils are found lying between the
  faucial pillars.

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c. The Laryngopharynx

• The laryngopharynx begins superiorly at the hyoid
  bone.
• Its inferior anterior border is the epiglottis.
• Its inferior posterior border is continuous with
  the esophagus.

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2. The Larynx

• The larynx is a cartilaginous structure supported
  in the neck by a series of flat strap muscles.

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2. The Larynx

• Its superior support is the hyoid bone.
• Its inferior point of attachment is the trachea.

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2. The Larynx

• The entire laryngeal structure is lined with
  mucous membrane.
• The underlining of the glottis, down to the
  trachea has a very rich, wet mucous membrane that
  constantly lubricates the vocal folds.

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2. The Larynx

• Nerve supply to the larynx is provided by the
  Vagus (Xth) cranial nerve.
• The blood supply is from a branch of the common
  carotid artery.

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2. The Larynx

• The larynx is comprised of three sets of folds
• The aryepiglottic folds are found at the upper
  rim of the larynx connected to the epiglottis.

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2. The Larynx

• The ventricular or false folds are thick bands of
  tissue above the glottis.
• The vocal (true) folds are the phonatory
  vibrators.

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2. The Larynx

• The space between the true and false folds is
  termed the ventricle.
• At the level of the vocal folds (glottis) the
  larynx is anatomically divided into two parts.
• The vestibule constitutes the supraglottic
  region.
• The atrium constitutes the infraglottic region

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B. Laryngeal Anatomy

• There are no bones in the larynx.
• The entire laryngeal framework is cartilaginous.
• However, the larynx is suspended from the hyoid
  bone, but it is not part of the larynx proper.
• All cartilages, ligaments, membranes, and muscles
  of the larynx are utilized in phonation.

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B. Laryngeal Anatomy

• The 9 cartilages of the larynx are the thyroid
  cartilage, the cricoid cartilage, the epiglottis,
  the paired arytenoids, the paired corniculates,
  and the paired cuneiforms.

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Cartilagesa. Thyroid Cartilage

• The thyroid cartilage is the most prominent
  cartilage.
• It is a type of hyaline cartilage comprised of
  two flat plates (laminae) fused together at an
  angle to form the laryngeal prominence.

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1. Cartilages a. Thyroid Cartilage

• In adult females, the angle of the laryngeal
  prominence is 120 degrees.
• In adult males, the angle is more acute at 90
  degrees.

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1. Cartilages a. Thyroid Cartilage

• Along the superior border of the thyroid
  cartilage is the thyroid notch.
• From the superior posterior edge of each lamina
  are the superior cornu.
• Inferiorly, the inferior cornu descend from the
  laminae.

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1. Cartilages a. Thyroid Cartilage

• The thyrohyoid ligament attaches the superior
  cornu to the hyoid bone.
• The ceratocricoid ligament attaches the inferior
  cornu to the cricoid cartilage.

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1. Cartilages b. Cricoid Cartilage

• The cricoid cartilage is found inferior to the
  thyroid cartilage.
• It forms a considerable portion of the posterior
  wall of the larynx.
• It is shaped like a signet ring, wider
  posteriorly than anteriorly.

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1. Cartilages b. Cricoid Cartilage

• On its lateral borders are articular facets which
  receive the inferior cornu of the thyroid
  cartilage.
• On its superior posterior surface are articular
  facets for the arytenoid cartilages.

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1. Cartilages b. Cricoid Cartilage

• Ligaments secure the cricoid cartilage to the
  thyroid cartilage and to the trachea.
• Specifically, the cricothyroid ligament secures
  the cricoid and thyroid cartilages.
• The cricotracheal ligament secures the cricoid
  cartilage to the first tracheal ring.

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1. Cartilages c. Arytenoid Cartilages

• The paired arytenoid cartilages are three-sided
  pyramidal structures that rest on the superior
  posterior border of the cricoid cartilage.

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1. Cartilages c. Arytenoid Cartilages

• Each arytenoid has a broad base and diminishes in
  size as it rises toward the apex.
• The lateral posterior base has a large knob-like
  projection called the muscular process.
• The medial anterior base has a small projection
  called the vocal process.
• The vocal process is the point of attachment for
  the vocal folds.

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1. Cartilages d. Corniculate Cartilages

• The paired corniculate cartilages are small
  elastic cartilages fused with the apex of the
  arytenoids.
• These seem to do little more than support the
  aryepiglottic folds.

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1. Cartilages d. Corniculate Cartilages

• Another pair of small elongated cartilages, the
  cuneiform cartilages, are embedded with the
  mucous membrane of the aryepiglottic folds.
• They support these folds during swallow, when the
  epiglottis moves to cover the larynx.

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Figure 1 The Corniculate Cuneiform Cartilages
in Situ
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1. Cartilages e. Epiglottis

• The flat, leaf-shaped cartilage rising out of the
  larynx is the epiglottis.
• It is attached inferiorly to the thyroid
  cartilage below the notch by the thyroepiglottic
  ligament.
• Superiorly it is attached to the body of the
  hyoid bone by the hyoepiglottic ligament.

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2. Laryngeal Muscles
34
2. Laryngeal Muscles

• The muscles found in the larynx are of two types
• The extrinsic muscles have one point of
  attachment external to the larynx.
• The intrinsic muscles have both points of
  attachment within the larynx.

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2. Laryngeal Muscles

• Most of the extrinsic muscles are responsible for
  either elevating or depressing the entire larynx,
  especially during swallow.
• In trained singers, the extrinsic muscles may
  help produce notes outside the normal singing
  range.

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2a. Extrinsic Laryngeal Muscles

• The suprahyoid muscles are those extrinsic
  muscles with a point of attachment above the
  hyoid bone.
• They raise the larynx for swallowing and high
  note singing functions.
• The infrahyoid muscles have a point of attachment
  below the hyoid bone.
• They lower the larynx after swallow and for low
  note singing functions.

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2b. Intrinsic Laryngeal Muscles

• There are 5 groups of intrinsic laryngeal
  muscles.
• They perform important functions in positioning
  the larynx for phonation.
• They are categorized by the actions they perform.

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2b. Intrinsic Laryngeal Muscles

• Abductors open the vocal folds.
• There is one pair of glottal abductors.
• Adductors close the vocal folds.
• There are two muscles that adduct the folds.
• Glottal tensors raise vocal pitch.
• There is one pair of muscles that lengthens the
  vocal folds.
• Glottal relaxers lower vocal pitch.
• There is one pair of muscles that shortens the
  vocal folds.

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2b 1). Abductors

• When the posterior cricoarytenoid muscle
  contracts, it pulls the muscular processes toward
  midline, which moves the vocal processes apart
  and abducts (opens) the vocal folds.
• It is located on the posterior lamina of the
  cricoid cartilage and attaches to the muscular
  process of the arytenoid cartilage.

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2b 2). Adductors

• The arytenoideus muscle, both the transverse and
  oblique portions, is a singular muscle running
  between the two arytenoid cartilages.
• When it contracts, it pulls the vocal processes
  toward midline and tips the apices forward to
  adduct (close) the vocal folds.

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2b 2). Adductors

• The paired lateral cricoarytenoid muscle attaches
  to either side of the cricoid cartilage and to
  the muscular process of each arytenoid.
• When it contracts, it pulls the muscular
  processes laterally, which approximates the vocal
  processes in adduction.

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2b 2). Adductors

• Heres is another view of the lateral
  cricoarytenoid muscle.
• You can see its insertion of the muscular process
  of the arytenoid cartilage.

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2b 3). Glottal Tensors

• Each pair of the cricothyroid muscle has two
  different fiber types vertical and oblique.
• These muscles originate at the lateral sides of
  the cricoid cartilage and insert into the
  posterior lamina of the thyroid cartilage.

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2b 3). Glottal Tensors

• When contracted, the muscle pulls down and tilts
  the thyroid cartilage forward.
• The vocal folds are stretched, which reduce their
  mass and results in a rise in pitch.

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2b 4). Glottal Relaxers

• The thyroarytenoid muscles, the muscular base of
  the vocal folds themselves, constitute the
  glottal relaxers.
• Contraction of this muscle draws the arytenoids
  toward the thyroid cartilage, increasing the
  thickness of the vocal folds, and lowering the
  pitch.

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2b 4). Glottal Relaxers

• The thyroarytenoid muscles originate on the
  internal surface of the thyroid cartilage near
  the angle.
• Each muscle has two fiber bundles.
• The thyromuscularis portion inserts into the
  muscular process of the arytenoid cartilage.
• The thyrovocalis portion inserts into the vocal
  process of the arytenoid process.

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3. Histology of the Vocal Folds

• Hirano (1974, 1981) has shown that the vocal
  folds are composed of five microscopically
  distinct tissue layers.
• The outermost layer, the epithelium, is a thin,
  stiff cover that maintains the shape of the vocal
  folds.

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3. Histology of the Vocal Folds

• Next we have the lamina propria.
• The superficial layer
• consists of loose fibers in a mass of soft
  gelatin.
• It is thought to serve as a shock absorber for
  the ligament, which is made up of the
  intermediate and deep layers.

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3. Histology of the Vocal Folds

• Finally, the thryoarytenoid muscle makes up the
  final layer of vocal fold tissue.
• It makes up the main body of the vocal fold and
  is capable of contraction.

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3. Histology of the Vocal Folds

• To understand vocal fold mechanics, it is easier
  to think of them as consisting of three sections
• A cover
• A transition and
• A body.

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3. Histology of the Vocal Folds

• The cover has the stiff thin epithelium and the
  underlying fluid-like mucosa
• The transition is the vocal ligament where large
  mechanical stress occurs.
• The body consists of the muscle itself which
  controls the shape of the VF and the degree of
  tonicity.

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3. Histology of the Vocal Folds

• For clear phonation, the margins of the vocal
  folds must be mobile.
• During phonation, the cover of the fold produces
  a wave-like motion.

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3. Histology of the Vocal Folds

• The undulating wave of movement travels from the
  lower surface to the upper surface of the VF in
  each cycle of vibration.
• Indeed, the mucous membrane cover vibrates more
  than the muscle during phonation.

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3. Histology of the Vocal Folds

• In patients with scarred or dry vocal folds, the
  mucosa loses its mobility, and phonation is
  breathy and elevated in pitch because the VFs are
  stiff not pliable.

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C. Laryngeal Physiology

• 1. Properties of Sound Waves

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1. Properties of Sound Waves

• Undisturbed air is in a state of equilibrium.
• When an external force impinges on the air
  particles, the may move closer together or
  farther apart, depending upon the location of the
  disturbance.
• Compression occurs when air molecules move closer
  together
• Rarefaction occurs when air molecules move
  farther apart.

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1. Properties of Sound Waves

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1. Properties of Sound Waves

• Like liquid, air is fluid, and molecules tend to
  flow from regions of higher pressure to regions
  of lower pressure.
• Air molecules also tend to remain in motion until
  the energy imparted has been dissipated.
• Like a rock thrown into an undisturbed pond, air
  molecules, like water ripples, will move outward
  in all directions, compressing the air ahead
  (increasing pressure) and leaving a drop in
  pressure behind.

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1. Properties of Sound Waves
60
1. Properties of Sound Waves

• A periodic air wave is generated any time there
  is a disturbance of air particles by force.
• As they travel through the air, progressive
  longitudinal wave forms are produced.

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a. Frequency

• Periodic air waves travel as pulses of
  compression and rarefaction from their point of
  origin.
• Each cycle of one compression and one rarefaction
  is termed an oscillation.
• Frequency, perceived as pitch, is dependent upon
  the number of oscillations or cycles per second.

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a. Frequency

• The perceived pitch of a sound increases in
  proportion to its frequency of oscillation.
• Frequency of oscillation is expressed in Hertz
  (Hz).

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b. Intensity

• The amplitude of a sound wave is determined by
  the amount of air particle displacement from its
  position of equilibrium.
• The greater the displacement of air particles,
  the larger the wave generated and the more
  intense the sound.

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b. Intensity

• Loudness is the perceptual correlate of the
  amplitude of a sound wave.
• The greater the amplitude the louder the sound.
• Intensity of sound is measured in decibels (dB).

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Figure 2 Sinusoidal Waves

• Looking at the sinusoidal wave on the overhead,
  consider the following
• Which waves have the same frequency?
• Which wave has the greatest amplitude?
• Which waves have the same amplitude?
• Which wave has the greatest frequency?

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2. Normal Voice Characteristics Variants

• A normal speaking voice has the following
  characteristics
• It operates on a mechanism which is structurally
  sound, free from disease, or pathologies
• It is esthetically pleasing.
• It is appropriate to the age, sex, and size of
  the speaker.
• It is physiologically efficient, producing
  maximum output with minimal energy.

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2a. Fundamental Frequency

• The fundamental frequency (fo) of the voice is
  determined by three things
• Vocal fold length
• Vocal fold tension and
• Vocal fold mass in combination with subglottic
  pressure.
• The measure of fo reflects the vibratory rate of
  the vocal folds during vowel prolongation tasks.

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2a. Fundamental Frequency

• Vocal fold length is greater for men than women,
  and greater for adults than children.
• It is during puberty that significant increases
  in vocal fold length occur.
• The male vocal fold increases 1/3 to 1/2 in
  length to range from 2/3 to 3/4 in total length.
• The female vocal fold increases 1/4 to 1/3 in
  length to range from 1/2 to 2/3 in total length.

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2a. Fundamental Frequency

• Vocal fold tension is determined by the
  relationship of the vocal folds to the cartilages
  to which they are attached.
• If the vocal folds are stretched and elongated by
  the contraction of the cricothyroid muscle, they
  will vibrate more quickly.
• If the vocal folds are lax and shortened by
  contraction of the thyroarytenoid muscles, they
  will vibrate more slowly.

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2a. Fundamental Frequency

• Vocal fold mass refers to the amount of vocal
  tissue, not to weight.
• Generally, the bigger the person, the greater the
  mass of his/her vocal folds.
• Changes in tension will change vocal fold mass.
• When vocal fold tension increases, the mass of
  the vocal fold is reduced.
• When vocal fold tension decreases, the mass of
  the vocal fold is increased.

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2a. Fundamental Frequency

• A voice of higher pitch is produced when the
  vocal folds are tense, thin (reduced mass), and
  vibrating quickly.
• A voice of lower pitch is produced when the vocal
  folds are lax, bulky (increased mass), and
  vibrating slowly.

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2b. Vocal Intensity

• Vocal loudness varies according the the
  respiratory airflow and subglottic air pressure
  passing through the glottis.
• Air pressure and airflow affect the size of the
  excursions (movement away from midline) executed
  by the vocal folds.

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3c. Relationship between Frequency, Intensity,
and Subglottic Air Pressure

• With natural vibration, frequency of vibration is
  based on natural mass of vocal folds and
  intensity is based on natural air pressure
  energy.
• An easy way to remember how frequency of
  vibration, intensity of vibration, and air
  pressure are inter-related is the Puff Theory.

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3c. Relationship between Frequency, Intensity,
and Subglottic Air Pressure

• The Puff Theory states that
• small, rapid puffs create soft, high pitch.
• large, rapid puffs create loud, high pitch.
• small, slow puffs create soft, low pitch.
• large, slow puffs create loud, low pitch.
• This is a short answer on the exam.

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3c. Relationship between Frequency, Intensity,
and Subglottic Air Pressure

• If an additional energy source is used to affect
  vibration, the mass must be altered in some way
  to keep the vocal folds closed beyond the time
  needed for a regular amount of subglottic air
  pressure to open them.
• Only muscle force can ensure extra resistance.
• Therefore, the vocal folds must tense, and that
  tension reduces mass, and pitch rises
  correspondingly.

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Figure 3. Stroboscopic View of Vocal Folds

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3d. Normal Vocal Variants

• On average, the habitual pitch level is estimated
  to be roughly 128 Hz in men, 225 Hz in women, and
  265 Hz in children.
• Maximum frequency ranges can extend from a low fo
  of 77 Hz to a high fo of 567 Hz in men
• In women, the average range is from a low fo of
  134 Hz to a high fo 895 Hz.
• Average intensity of conversational speech 3
  from the listener is 60 dB.
• Quiet speech is 35-40 dB and loud speech can
  exceed 110 dB.

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3e. Vocal Registers

• The shape, length, density, and elasticity of the
  vocal folds alter constantly in the production of
  notes of different frequency.
• The vibratory pattern of the vocal folds and the
  acoustic parameters they produce can be changed
  over some ranges of pitch and loudness.

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3e. Vocal Registers

• Three perceptually distinct registers of vocal
  quality have been identified (Hollien, 1974).
• For speaking they are called pulse (fry)
  modal and falsetto (loft).
• For singing, they are called chest head and
  falsetto.

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3e. Vocal Registers

• To produce a vocal fry, the thyroarytenoid
  muscles are active.
• As they shorten, the vocal folds thicken, which
  results in their remaining closed over an
  appreciable part of each cycle of vibration.

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3e. Vocal Registers

• Vocal fry is a fairly common occurrence in
  everyday speech.
• Sometimes known as creaky voice, it is frequent
  in vocal strain and abuse.
• The frequency involved is within the 20-60 Hz
  range.

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3e. Vocal Registers

• The modal register encompasses the range of notes
  employed most frequently in normal phonation.

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3e. Vocal Registers

• The falsetto register occurs in human vocal
  activities such as singing, war cries, yodeling,
  and giggling.
• The thyroarytenoid muscles are passive offering
  little resistance to the cricothyroids, which
  apply substantial longitudinal tension to the
  vocal folds, lengthening and thinning the vocal
  ligaments.
• In phonation, the glottis closely only briefly,
  or not at all, allowing only the edges of the
  vocal folds (vocal ligaments) vibrate. 

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3f. Vocal Attacks

• To initiate phonation, subglottic air pressure
  builds up under the vocal folds which are closely
  approximated in midline.
• There are three basic vocal or phonatory attacks.
• Simultaneous attack
• Glottal attack and
• Breathy attack.

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3f. Vocal Attacks 1) Simultaneous Attack

• Simultaneous attack results when vibration of the
  vocal folds begins just as air is being released
  and the vocal folds are approximating in midline.
  
• When there is simultaneous release of air
  pressure through the glottis and onset of
  phonation, the attack is healthy and not
  damaging.

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3f. Vocal Attacks 2) Glottal Attack

• Some phonatory initiation results from laryngeal
  hyperfunction.
• The glottal attack is such a form of laryngeal
  hyperfunction.
• With hyperfunction, the entire laryngeal
  apparatus is tensed.
• Physiologically, a hard glottal attack is
  produced by firmly compressing the vocal folds at
  the midline before phonation.
• The breath stream is then released explosively as
  exhalation begins

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3f. Vocal Attacks 3) Breathy Attack

• Onset of phonation that results from laryngeal
  hypofunction is termed a breathy or aspirate
  attack.
• In the soft attack, the vocal folds are being
  adducted while there is an air flow through the
  glottis.
• While this type of attack rarely damages the
  vocal cords, it causes a breathy tone quality.
• This technique may, however, be utilized to help
  correct a hard glottal attack.