Anatomy of the vocal mechanism
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Phonation
• Myoelastic aerodynamic theory of
phonation.
• Fundamental frequency
• Harmonics
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Phonation
• Production of sound in larynx.
• Anytime you use voicing to produce a
sound (e.g., vowels and voiced consonants)
phonation will take place.
• Myoelastic aerodynamic theory of
phonation (see next slide)
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Myoelastic Aerodynamic Theory
of Phonation
• Two stage process
• Stage one: Myoelastic phase. Elasticity of
vocal folds helps them close.
• Stage two: Aerodynamic phase
– Sub-glottal pressure forces vocal folds apart
– Bernoulli Effect helps vocal folds close
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Bernoulli Effect
• As air velocity
increases, air
pressure
decreases.
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Myoelastic Aerodynamic Theory
of Phonation (continued)
• Another way of stating the MA theory is to
see how vocal folds open and close.
• Opened due to…
– Increase in subglottal pressure
• Closed due to…
– Vocal fold elasticity
– Bernoulli effect
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Fundamental Frequency
•
•
Refers to the fundamental frequency to which the
vocal folds vibrate at.
Variables that affect fundamental frequency (fo)
1. Gender and age
•
•
•
Males
Females
Children
120 Hz
220 Hz
270-300 Hz
2. Mass (relaxing and tensing of vocal folds)
3. Intensity (Bernoulli effect)
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Harmonics
• Discussed during acoustics section.
• Remember…
– During phonation you will fo along with a
series of harmonics
– Spacing between harmonics will equal the fo.
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Harmonics
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Jitter and Shimmer
• Jitter
– Variations in the Fo, aka frequency perturbation
– Periods between individual cycles vary slightly
(e.g., 200, 201, 199 Hz, etc.)
• Shimmer
– Variations in Intensity, aka amplitude
perturbation
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Jitter and Shimmer continued
• Causes of jitter and shimmer
–
–
–
–
Neurological
Biomechanical
Aerodynamic
Acoustic (hearing loss)
• Normal values
– Jitter (0.2 to 1%) of frequency
– Shimmer (< 0.5 dB)
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Jitter and Shimmer continued
• Clinical Applications
– Vocal aging
• Increased for children and elderly
– Neurological pathology
• Parkinson’s Disease
• Amyotrophic Lateral Sclerosis
• Laryngeal Cancer
– Increased vocal fold mass (e.g., nodule, polyp, etc.)
– Stuttering in young children (shimmer)
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Vocal Registers
•
•
•
•
Pulse
Modal
Midvoice
Falsetto
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Pulse
• Vocal frequency is 30 to 80 Hz in males and 90 to
165 Hz in females.
• VFs are closed about 90% or time and open 10%.
• Perceived as burst of acoustic energy but with
silence gaps.
• Normal at end of phrases and sentences.
• Clinical problem if used habitually.
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Modal and Midvoice
• Modal
– About 100 to 150 Hz in males
– About 175 to 300 Hz in females
– Perceived as normal speech
• Midvoice
– About 200 to 300 Hz in males
– About 350 to 600 Hz in females
– Often used in singing situation
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Falsetto
• Vocal frequency of about 350 to 500 Hz in
males.
• About 650 to 1000 Hz in females.
• Vocal folds may not meet in middle because
of abnormal tension and may be breathy
• “Reedy sound” due to widely spaced
harmonics.
• Falsetto’s are not a part of normal speech.
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Summary
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