Phonation + Vocal Fold Physiology
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Transcript of Phonation + Vocal Fold Physiology
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Phonation + Vocal Fold Physiology
Feburary 6, 2013
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Average Everydayness• Production exercise comments and grades were e-mailed shortly before class;
• I’m sending the second one out tonight.
• Will be due next Wednesday…
• Today:
• The Wonderful World of the Larynx!
• But first: a completely random linguistic detour...
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The Kiki/Bouba Experiment• Originally devised by psychologist Wolfgang Köhler in 1927.
• Updated and replicated in 2001.
• Look at these two figures:
• Which one is bouba and which one is kiki?
• ~95% of both English and Tamil speakers thought the shape on the left was “kiki”, the one the right “bouba”
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Where Were We?• Air squeezed out of the lungs travels up the bronchi...
• Through the trachea (windpipe)
• To a complicated structure called the larynx.
• ...where phonation happens.
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The Larynx• The larynx is a complex structure consisting of muscles, ligaments and three primary cartilages.
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1. The Cricoid Cartilage• The cricoid cartilage sits on top of the trachea
• from Greek krikos “ring”
• It has “facets” which connect it to the thyroid and arytenoid cartilages.
cricoid cartilage
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2. The Thyroid Cartilage• The thyroid cartilage sits on top of the cricoid cartilage.
• from the Greek thyreos “shield”
• The thyroid cartilage has horns!
• Both lower (inferior) and upper (superior) horns
• The lower horns connect with the cricoid cartilage at the cricoid’s lower facet.
• The upper horns connect to the hyoid bone.
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Thyroid Graphic
thyroid cartilage
cricoid cartilage
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Thyroid Angles• The two broad, flat front plates of the thyroid--the laminae--meet at the thyroid angle.
• The actual angle of the thyroid angle is more obtuse in women.
• ...so the “Adam’s Apple” juts out more in men.
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3. The Arytenoid Cartilages• There are two arytenoid cartilages.
• from Greek arytaina, “ladle”
• They are small and pointy, and sit on top of the back side, or lamina, of the cricoid cartilage.
arytenoid cartilages
cricoid cartilage
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The Vocal Folds• These three cartilages are connected by a variety of muscles and ligaments.
• The most important of these are the vocal folds.
• They live at the very top of the trachea, in between the cricoid and thyroid cartilages.
• The vocal folds are a combination of:
• The vocalis muscle
• The vocal ligament
• The vocal folds are enclosed in a membrane called the conus elasticus.
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• Just above the true vocal folds are the “false” (!) vocal folds, or ventricular folds.
• The space between the vocal folds is the glottis.
Vocal Fold View #1
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Vocal Fold View #2• The vocal ligaments attach in the front to the thyroid cartilage.
• ...and in the back to the arytenoid cartilages.
• The glottis consists of:
• the ligamental glottis
• the cartilaginous glottis
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Things Start to Happen• Note that the arytenoid cartilages can be moved with respect to the cricoid cartilage in two ways.
#1: rocking #2: sliding
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The Upshot• The arytenoids can thus be brought together towards the midline of the body.
• Or brought forwards, towards the front of the thyroid.
• The rocking motion thus abducts or adducts the glottis.
• The sliding motion shortens or lengthens the vocal folds.• Check out the arytenoids in action.
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• When the vocal folds are abducted:
• air passes through the glottis unimpeded and voicelessness results.
• The posterior cricoarytenoid muscles are primarily responsible for separating the arytenoid cartilages.
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• Voicing may occur when the vocal folds are adducted and air is flowing up through the trachea from the lungs.
• Two muscles are primarily responsible for adducting the vocal folds.
• The first is the lateral crico-arytenoid muscle.
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• Note that the lateral cricoarytenoid muscles only adduct the ligamental glottis.
• The transverse arytenoid muscles pull together the arytenoid cartilages themselves.
• Thereby closing the cartilaginous glottis.
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The Consequences• The combined forces drawing the vocal folds towards each other produce adductive tension in the glottis.
• Adductive tension is increased by:
• lateral cricoarytenoid muscles
• transverse arytenoid muscles
• Adductive tension is decreased by:
• posterior cricoarytenoid muscles
• Adduction vs. abduction determines whether or not voicing will occur.
• But we can do more than just adduce or abduce the vocal folds...
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Controlling F0• Question: why do women have a higher F0 than men?
• A: Shorter vocal folds open and close more quickly.
• In men:
• Ligamental glottis 15.5 mm
• Cartilaginous glottis 7.5 mm
• Total glottis length 23 mm
• In women:
• Ligamental glottis 11.5 mm
• Cartilaginous glottis 5.5 mm
• Total glottis length 17 mm
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Factor Two
• F0 also depends on the longitudinal tension in the vocal folds.
• I.e., tension along their length, between the thyroid and arytenoid cartilages.
• Higher tension = higher F0
• Lower tension = lower F0
• Q: How can we change longitudinal tension in the larynx?
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• A: We can rotate the thyroid cartilage up and down on its connection with the cricoid cartilage.
• ...like the visor of a knight’s helmet.
• This either stretches or relaxes the vocal folds.
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Contradictory?• No, just complicated. Note:
• Lengthening (stretching) the folds results in higher tension
• ...which results in higher F0
• Shortening the folds results in less tension
• ...which results in lower F0
• “Higher” and “lower” F0 have to be understood relative to the speaker’s normal F0 range.
• still lower for men
• still higher for women
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For the Record• Contraction of the cricothyroid muscle pulls down the thyroid cartilage.
• Interestingly: researchers often study the activity of this muscle using EMG.
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Fun Stuff (= tracheotomy)Peter Ladefoged: “To record the pressure of the air associated with stressed as opposed to unstressed syllables we need to record the pressure below the vocal folds. A true recording of the subglottal pressure can be made only by making a tracheal puncture.This is a procedure that must be performed by a physician. A local anesthetic is applied both externally and inside the trachea by means of a fine needle. A larger needle with an internal diameter of 2 mm can then be inserted between the rings of the trachea as shown in figure 3.3”
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Figure 3.3
“As you can see from my face it is not at all painful. But it is not a procedure that can be carried out in fieldwork situations.”
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For the Record, part 2• Longitudinal tension can also be reduced by the thyroarytenoid muscles.
• Which connect the thyroid to the arytenoid cartilages.
vocal folds
• These muscles are inaccessible to EMG
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Check it out!• Let’s look at some pitch shifting laryngoscopy videos.