Respiration + Vocal Fold Physiology
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Transcript of Respiration + Vocal Fold Physiology
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Vocal Fold Physiology + Voice Quality
October 9, 2014
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Average Everydayness• Don’t forget to send me your second production exercises by Monday!
• Also: course project report #2 is due on Tuesday.
• Today:
• The Wonderful World of the Larynx!
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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.
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Factor #3• Increasing longitudinal tension also makes the vocal folds thinner.
• Thinner vocal folds open and close more quickly.
• Average thickness of male vocal folds =
• 2-5 mm
• Female folds are somewhat thinner
low F0
mid F0
high F0
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Frequency and Vowels• In the mystery tone language exercise, you may have noticed that the fundamental frequency of [i] was slightly higher than that of [a], for the same tones
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“Intrinsic” Pitch• It’s been observed that F0 is usually higher for high vowels than for low vowels
[i] 183 Hz
[e] 169
[æ] 162
[a] 163
[o] 170
[u] 182
• Data from Lehiste & Peterson (1961) for American English
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• The “Tongue Pull” Hypothesis (Honda, 2004):
• Raising the tongue for high vowels also raises the larynx
• The cricoid cartilage rises up and around the spine…
• Thus stretching the vocal folds
• and increasing longitudinal tension.
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An Intrinsic Summary High Vowels Low Vowels
Intensity Less More
Duration Shorter Longer
F0 Higher Lower
• A word of caution:
• All of these factors (intensity, duration, F0) factor into perceived prominence and stress.
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Contact!• Interesting (and important) fact: the vocal folds do not open and close all at once.
• Their upper and lower parts open and close out of phase with each other.
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Implications• Glottal opening and closing forms a complex wave.
• The out-of-phase factor is reduced with thinner vocal folds.
• i.e., the glottal cycle becomes more sinusoidal
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Electroglottography• The degree of vocal fold separation during voicing can be measured with a method known as electroglottography (EGG)
• Electrodes are placed on either side of the larynx
• More contact between vocal folds greater conductivity between electrodes
• A caveat:
• tends to work better on men than women.
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EGG Readout
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EGG Output
“The north wind and the sun were disputing which was the stronger, when a traveler came along wrapped in a warm cloak.”
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An EGG Schematic1. Complete closure of vocal folds
conductivity
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An EGG Schematic2. Lower half of folds begin to open
conductivity
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An EGG Schematic3. Upper half of folds open
conductivity
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An EGG Schematic4. Folds are completely apart
conductivity
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An EGG Schematic5. Lower half of folds begin to close
conductivity
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An EGG Schematic6. Upper half of folds close
conductivity
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An EGG Schematic7. Folds are completely closed, again
conductivity
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An Actual EGG Waveform• Modal voicing (by me):
• Note: completely closed and completely open phases are both actually quite short.
• Also: closure slope is greater than opening slope.
• Q: Why might there be differences in slope?
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Factor #5• There is another force at work: medial compression.
• i.e., how tightly the folds themselves are compressed against each other.
• Medial compression determines, to some extent, how quickly/slowly the folds will open.
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MC Forces, yo• Medial compression is caused by constriction of:
1. The lateral cricoarytenoids
• which adduct the vocal folds
2. The thyroarytenoids
• which pull the arytenoids towards the thyroid
• But not the interarytenoids
• ...which only squeeze the arytenoid cartilages together
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For the Record, part 3• It is not entirely clear what the role of the vocalis
muscle plays in all this.
• The vocalis muscle is inside the vocal folds
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The Vocalis Muscle1. It may also shorten the vocal folds through contraction
• thereby potentially lowering longitudinal tension
• and lowering F0
2. However, the same contraction would increase medial compression within the vocal fold
• thereby decreasing vocal fold thickness
• and increasing F0
• Researchers still need to figure out a way to get at this muscle while it’s in action…
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Vocal Fold Force Summary1. Adductive Tension
• between arytenoids + folds
2. Longitudinal Tension
• stretches vocal folds
3. Medial Compression
• squeezes vocal folds together
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1. Modal Voice Settings• At the low end of a speaker’s F0 range:
1. Adductive tension force is moderate
2. Medial compression force is moderate
3. Vocal folds are short and thick.
• = longitudinal tension is low
4. Moderate airflow
• F0 is increased by:
1. Increasing the longitudinal tension
activity of the cricothyroid muscle
2. Increasing airflow
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A Different Kind of Voicing• Tuvan throat singing (khoomei):
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A Different Kind of Voicing• The basic voice quality in khoomei is called xorekteer.
• Notice any differences in the EGG waveforms?
• This voice quality requires greater medial compression of the vocal folds.
• ...and also greater airflow
• Check out the tense voice video.
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Modal vs. Tense Voice• The language of Mpi contrasts modal voice vowels with tense voice vowels.
• Mpi is spoken in northern Thailand.