Phonatory System Lecture 8

The Larynx (Anatomy Review) Bone Cartilage Ligament Membrane Muscle

The Larynx Innervation Extrinsic muscles Intrinsic muscles How the vocal folds vibrate Initiating vibration Pitch Registers

Innervation Vagus (CN X) Superior laryngeal nerve: Cricothyroid (CT) Recurrent laryngeal nerve: Thyroarytenoid (TA) Posterior Cricoarytenoid (PCA) Lateral Cricoarytenoids (LCA) Interarytenoids (IA) Blumenfeld, H., 2002, Neuroanatomy through Clinical Cases, Sinauer, Inc.

Extrinsic Laryngeal Muscles Many extrinsic laryngeal muscles Thyrohyoid Elevates larynx Sternothyroid Depresses larynx Hixon, T.J., et al. (2008). Preclinical Speech Science: Anatomy Physiology Acoustics Perception. Pg. 112.

The Larynx Innervation Extrinsic muscles Intrinsic muscles How the vocal folds vibrate Initiating vibration Pitch Registers

Thyroarytenoid Bulk of the vocal folds Contractions can result in: Shortening the vocal folds Pulling thyroid and arytenoid cartilages toward each other Increasing the tension of the vocal folds Isometric (contracting and not changing length) Shorten: decreases pitch Increase tension: increases pitch Hixon, T.J., et al. (2008). Preclinical Speech Science: Anatomy Physiology Acoustics Perception. Pg. 98.

Cricothyroid When it contracts, it helps to lengthen the vocal folds It elevates the cricoid arch, and depresses the thyroid lamina (shortens the space between the cricoid and the thyroid) This can help to increase pitch Hixon, T.J., et al. (2008). Preclinical Speech Science: Anatomy Physiology Acoustics Perception. Pg. 97.

TA and CT: Activation Patterns CT active and TA passive = increase pitch Increase length Increase stiffness TA active and CT passive = decrease pitch Decrease length Decrease stiffness TA and CT contract simultaneously = increase pitch

Posterior and Lateral Cricoarytenoids Work in opposition PCA: Rocks arytenoids away from midline Opens the vocal folds LCA: Rocks arytenoids toward midline Closes the vocal folds Hixon, T.J., et al. (2008). Preclinical Speech Science: Anatomy Physiology Acoustics Perception. Pg. 100.

ABduction & ADduction PCA: LCA: Rocks arytenoids away from midline ABducts the vocal folds LCA: Rocks arytenoids toward midline ADducts the vocal folds Hixon, T.J., et al. (2008). Preclinical Speech Science: Anatomy Physiology Acoustics Perception. Pg. 107.

Interarytenoids Transverse: Oblique: Pulls arytenoids toward each other ADducts the vocal folds Oblique: Tips one arytenoid (apex) toward the other (body) Hixon, T.J., et al. (2008). Preclinical Speech Science: Anatomy Physiology Acoustics Perception. Pg. 101.

The Larynx Innervation Extrinsic muscles Intrinsic muscles How the vocal folds vibrate Initiating vibration Pitch Registers

Vocal Fold Vibration Many theories of vocal fold vibration Myo-elastic aerodynamic theory of vocal fold vibration Nonuniform tissue movement: Multimass models

Myo-elastic aerodynamic theory Van den Berg, 1958 Based on Bernoulli equation: P + ½ pv2 = constant P = pressure p = fluid density v = velocity Please use this formula- I believe the formula in your book is incorrect. This equation states that as pressure increases, velocity decreases (assuming density is constant) Based on Titze, I.R. (2000). Principles of Voice Production.

Myo-elastic aerodynamic theory Van den Berg, 1958 Based on Bernoulli equation: P + ½ pv2 = constant Basics of this theory: When the vocal folds are closed, pressure builds in the subglottal region When the pressure is high enough, it forces the vocal folds open The vocal folds continue to open further as air rushes out Once they reach a maximum opening, the elasticity in the vocal folds pulls them together The cycle repeats

Nonuniform tissue movement: Multimass models Other theories in between, but this is the most recent Explains self-sustained oscillation: as the vocal folds continue to oscillate (vibrate), they are able to sustain the same velocity and width of excursion Titze, I.R. (2000). Principles of Voice Production.

Nonuniform tissue movement: Multimass models Upper and lower parts of the vocal folds do not move as one The lower part of the vocal folds moves first, followed by the upper part Convergent: lower further apart than upper Divergent: upper further apart than lower Titze, I.R. (2000). Principles of Voice Production.

The Larynx Innervation Extrinsic muscles Intrinsic muscles How the vocal folds vibrate Initiating vibration Pitch Registers

Initiating vibration Phonation threshold pressure (PTP): smallest subglottal pressure needed to start self-sustained oscillation For low frequency phonation, PTP is around 3-4 cm H20

Pitch and Registers Average pitch: Registers Women: 220 Hz Chest (Low pitches) Men: 130 Hz Middle/Mixed (Middle pitches) Head/Falsetto (High pitches) Zemlin, pg 166.