Laryngeal System, Part 2.2 - PAP PDF

Physiology-Laryngeal System- Part 2 Muscles of Larynx Intrinsic Have origin and insertion within larynx Extrinsic Have one point of attachment  larynx and other attachment  other structure 2 INTRINSIC MUS...

Physiology-Laryngeal System- Part 2 Muscles of Larynx Intrinsic Have origin and insertion within larynx Extrinsic Have one point of attachment  larynx and other attachment  other structure 2 INTRINSIC MUSCLES OF LARYNX Abduct (open) or adduct (close) the folds. Vocal fold length and tension. Attach at origin and insertion of different cartilages Roles in respiration, swallowing, and vocalization. 3 4 Post. Ant. 55 Cricothyroid Muscle Attached to thyroid and cricoid cartilages Rocks thyroid forward; stretching and tensing the vocal folds Raises pitch –push on this and mechanically raise your pitch! 6 Intrinsic Muscles Main| Adductors| | Only Abductor  Raises pitch  Together make Up vocal folds 7 The Only ABDUCTION MUSCLE Posterior Cricoarytenoids (PCA) Opening the glottis Move arytenoids away from midline 8 Abduction Adduction 9 Adductor Muscles Move arytenoids to midline Rock forward Inter-arytenoids (Transverse and Oblique) Lateral Cricoarytenoids 10 Extrinsic Muscles “One attachment to a laryngeal and an external structure” SUPRAHYOID INFRAHYOID Stylohyoid Sternohyoid Digastric Sternothyroid Mylohyoid Thyrohyoid Geniohyoid Omohyoid 11 Suprahyoid muscles Pulls the entire larynx upwards in the neck. These large up and down movements occur mainly during swallowing. 12 Stylohyoid Muscle Digastri c 14 Mylohyoid Muscle Geniohyoid Muscle Suprahyoid muscles Infrahyoid muscles When contracted, pull the entire larynx downward 18 3 Branches – Vagus (CN X) (upper = sensory Pharyngeal Nerve) Superior Laryngeal Nerve sensory Recurrent Laryngeal Nerve motor motor 24 VF in the Midline-Now What? The process of getting the VF from an abducted to a partially/completely adducted position is called Pre-Phonation Phase Once in the midline, the initial few vibratory cycles are referred to as the Attack phase Complete adduction is not needed for VF vibration to begin Typically, the expiratory air flow (triggered by the respiratory system) and vocal fold approximation happen at the same time With the a) VF in the midline, b) presence of medial compression and c) longitudinal tension and d) generation of P-sub, we expect VF to begin vibrating VF in the Midline-Now What? Questions to consider: How are the vibrations created in the first place and how they are sustained (i.e., Theories!!) Role of Bernoulli effect Various physical variables Impacting VF vibrations Description of ONE VF vibration!! Theories of Voice Production/VF Vibrations Neurochronaxic Theory (Husson, 1950) Every new vibratory cycle is initiated by a nerve impulse transmitted via the X nerve Frequency of the VF vibration is dependent on the rate at which the impulses are transmitted Problems The course of the RT and the LT X nerve are different in length (about 10cm) VF don’t vibrate without the air stream Myoelastic Theory of Phonation Orig. by Johannes Muller (1858), then Janwillem van den Berg (1958) Basically accurate (but with some RECENT revision) Myo = muscle, Elastic = recoil Pulmonic air = active force; vocal folds = passive actors Johannes Müller 28 VOCAL FOLD VIBRATION Muscle Action Subglottal pressure build-up > Subglottal than supra-glottal pressure Creates delta force Pressure drop, Bernoulli effect 29 Vocal Fold Vibration The process of Adducting the vocal folds (pre-phonation phase) needs to involve the following processes Medial Compression: the act of getting the vocal process in the midline and compressing it in that position (LCA and IA) Longitudinal Tension: relative tension of the membranous portion of the vocal folds (CT and TA) As a result, the air stream moving out of the laryngeal system is stopped Vocal Fold Vibration Stopping the outgoing air stream results in an increase in pressure below the adducted vocal folds The increased pressure is the Sub-glottal pressure (Psub) This pressure (a minimum of 3-5 cmH20) will eventually burst open the adducted vocal folds, setting them into vibrations In summary, the interaction of the air flow with the vibrating surface of the vocal folds will result in glottal pulses; But how is it sustained Questions….questions… Medial compression involves increasing tension of the VF True False The pressure created below the glottis when the VF is adducted is ____ Supraglottic pressure Sub-glottic pressure We need more than 20 CmH20 Psub to burst the VF open and vibrating True False Daniel Bernoulli (1700 – 1782) The man The stamp The effect  33 The Bernoulli effect Once Psub is about 3-5 CmH20, the air stream burst the adducted VF and starts to pass through a narrow constriction i.e., the glottis As the air stream pushes itself in an upward direction, the velocity of the air column passing through the glottis will increase/higher when compared to the velocity of air in the trachea The difference in velocity is because the cross-sectional area is smaller at the glottis when compared to the trachea The Bernoulli effect As a result, a negative pressure develops perpendicular to the flow of air between the medial edges of the vocal folds Thus, the negative pressure sucks the medial edges of the vocal folds towards each other, resulting in the completion of one cycle Details about the Pressure velocity Relationships Why is negative pressure generated, how is it related to velocity and why is velocity increased in the first place The rate at which a given quantity of mass (in this case air) flows through a tube is a product of the density of the mass, the velocity of the mass and the cross-sectional area of the tube and this relationship is constant Therefore, at the glottis the cross-sectional area is smaller when compared to the trachea; This results in an increase in the velocity to Details about the Pressure velocity Relationships Now, velocity of the air column and Pressure in the tube are directly proportional as well and their product is always a constant Therefore, if the velocity of the air column at the glottis will increase as it moves through the glottis, the pressure has to decrease at the level of the glottis in order to keep the product constant Theories of Voice Production/VF Vibrations The Bernoulli effect alone cannot sustain self-oscillation of vocal folds Modified version of the Myoelastic aerodynamic theory addresses this issue The modified MyoElasticAeroDynamic Theory alongside other recent theories of VF vibration consider a variety of physical forces/properties (particularly recoil/passive forces) contributing to the vocal fold vibration in addition to Bernoulli effect What are these “Physical” Properties? The following physical properties have been considered by theories as impacting the nature of VF vibration Viscoelasticity of the vocal fold layers and its role in modifying the glottis configuration Stress-Strain relationships between the vocalis muscle and the superficial layers of the vocal folds variety of mechanical forces effecting the vocal folds differently on the lower and upper margins AND ALL THE OTHERS IN THE NEXT FEW SLIDES What are these “Physical” Properties? Laryngeal Opposing Pressure (“horizontal angle”): net opposing pressure when VF are adducted; this pressure varies depending on the activity Medial compressive force- most important Surface tension between the two moist VF surfaces Gravity What are these “Physical” Properties? Laryngeal Airway Resistance (“vertical angle”): resistance offered as air is flowing out of the glottis; directly related to the rate of air flowing out (more air flow, less resistance offered) Measured indirectly be calculating the quotient of Translaryngeal air pressure to air flow and pressure: What are these “Physical” Properties? Glottal Size and Configuration: changes can be made to different aspects of the VF- length, diameter, area, and shape These variables can be modified by selectively engaging the intrinsic muscles and result in a variety of glottal shapes completely open (during deep inspire)- PCA Medium to small opening (during TV breathing)- slight LCA and IA contraction Opening at the posterior end (at the start of VF vibration)- Just LCA Complete closure- strong LCA and IA contraction Muscosal wave Longitudinal Vertical phase phase difference difference (see (from posterior to next 2 slides) anterior, “like a zipper”) 47 ANT POST Note: In middle snapshots we also see “longitudinal” phase difference” - Kent, Speech Sciences 48 Vocal Fold Phonation Determined by mass, length, and tension Changes throughout utterance (question vs. statement, etc.) Males (F0: 80-150Hz) Females (180-250 Hz) Children (250-300 Hz) 49 Animations VF modal VF falsetto 50  What are these “Physical” Properties? Stiffness: how rigid or non-compliant is the VF VF inherently are stiffer at the points of attachment when compared to the midpoints Across layers, outer layers are less stiff than inner ones Stiffness can be increased by TA (increases Tension in vocalis) and CT (increases length) VF Mass: While VF MASS does not change, The mass of VF that comes into contact or set into vibrations will change So how does this happen?? VF are adducted by PCA True False The LCA helps with maintaining VF in the midline True False +ve pressure is created when air rushed through the VF after it is burst open True False Describe 1 Vocal Fold Vibration Different phases of VF vibration Closed phase Opening phase Closing phase Displacement or Mode of VF vibration Displacement along the horizontal plane Displacement along the vertical plane Mucosal displacement /Mucosal wave Describe 1 Vocal Fold Vibration The Anterior 2/3rd of the vocal folds is primarily vibrating as it is membranous The posterior 1/3rd is cartilaginous The horizontal plane of VF vibration has the maximum displacement, with the posterior sections opening first followed by the more anterior sections the direction is the opposite during closing (analogous to the zipper action) Describe 1 Vocal Fold Vibration There is some displacement in the vertical plane as well wherein the lower edges of the VF open first and is followed by the upper edges. The same occurs during closing Due to the viscoelastic properties of the VF, the bernoulli effect/pressure difference influence the lower margins of the vocal folds more so than the upper margins Describe 1 Vocal Fold Vibration Mucosal Wave As there is a simultaneous horizontal and vertical movement, the COVER (1st 3 layers of the vocal folds-Epithelium, SLP, and ILP) is able to slide over the rest of the layers (DLP and BODY of the VF-TV muscle) The slide happens as the cover is loosely coupled to the underlying surfaces This generates a wave that moves along the superior surface of the VF and travels about 2/3rd of the way to the lateral edge. Abnormalities usually disrupt this movement and is the first sign associated with a change of voice quality. So how is the VF vibration sustained? VF separation along the vertical + horizontal dimension AND the movement of the VF layers in a mucosal wave results in pressure differences below and above the glottis during EACH VF vibration Refer to the ‘Convergent’ and ‘Divergent’ picture for more information Essentially the alternating Convergent and Divergent glottal shapes + airflow/pressure changes below and above the BF sustains VF vibration Summary…How are VF set in to Vibrations? Combination of a variety of resources Laryngeal system is preset for voice production by the neural system This facilitates the co-ordination with the respiratory system VF adduct/partially adduct resulting in increased Psub This bursts the VF seal and with air beginning to escape, it interacts with the VF layers that are inherently pliable This also results in –ve pressures that sucks the VF back This complex interaction of air flow from the lungs, unique VF anatomy and its physical properties and neural priming results in VF vibration What’s with the ‘view’ The movement of the VF in the horizontal plane happens 1st , followed by the vertical and then finally, there is the mucosal wave True False F0 and Harmonics  The human voice is nearly periodic 60 Glottal Spectrum Glottal F0 with harmonics Does not represent what is heard (due to vocal tract modulation) The F0 corresponds to the perceived pitch of the voice The harmonics contribute to the quality of the voice This is what we would see if we lowered a microphone down just over the larynx 61 F0 & Harmonic Spacing Adult Male Adult Female Child 62 Roll Off—F0 “About 40 harmonics have at least some acoustic energy in the human voice” 63 Vocal Registers Pulse (= Fry, Creaky) Modal Falsetto (cf. Table 5.5) 64 Registers – continued Falsetto Pulse – – Folds Folds closed 90% long and of time stiff, biphasic or Thinner quality multiphasic sound Leaves an acoustic temporal gap 65 Electroglottography (EGG) Best at detecting closing phase More contact between vocal folds greater conductivity between electrodes Works better on men than women 66 EGG Readout 67 EGG – Lx wave Reflects surface area of contact of the vocal folds “Duty cycle” of vocal fold vibration 68 Lx wave – continued CLOSING OPENING 2. Btwn b - c, 3. Btwn d-e superior inferior margins margins closing separate 1. Btwn a - b, 4. At e (“knee”) lower – superior margins begins closing to open 5. By f, width of glottis is widest 69 EGG quotients OP – open phase CP closed phase CQ closed quotient = CP/P Closed to open ratio = CP/OP Etc. 70 Open Quotient = time glottis is open period of voicing cycle Reliable differences between the three voicing types: Breathy  high open quotient Creaky  low open quotient Modal  in-between 71 Open Quotient Samples 72 Hyper- hypo- adduction Hyper - Vocal abuse, spastic dysphonia; takes more Ps to overcome resistance of folds Hypo – inappropriate usage, VF paralysis; VFs do not offer enough resistance 73 Abnormal voice (dysphonia) Breathiness (aspirated) Roughness (raspiness /low pitch) Hoarseness (combination) 74 (Clinical) Vocal Quality No clear acoustic Some common Terms correlates Breathy However, clinical terms Tense/strained suggest distinct Rough categories Hoarse 75 Tools for acoustic analysis Praat, TF32, Wavesurfer etc. 76 Jitter, Shimmer - Sample computing in TF32 program  77 Period/frequency & amplitude variability A. Jitter -: variability in the period of each successive cycle of vibration (A) B. Shimmer: - variability in the amplitude of each successive cycle of vibration (B) A B 78 Jitter and Shimmer Sources Measuring Small structural asymmetries of vocal folds Variability in measurement approaches “Material” on the vocal folds (e.g. mucus) …and how measures are reported Biomechanical events, such as raising/lowering the larynx in the Jitter neck Typically reported as % or msec Small variations in tracheal Normal ~ 0.2 - 1% pressures “Bodily” events – system noise Shimmer Can be % or dB Norms not well established 79 Harmonic to Noise Ratio (HNR)  Noise is introduced into the vocal signal via irregular or asymmetric adduction of the vocal folds.  Too much noise is perceived as hoarseness ( = lower HNR)  Laryngeal pathology may lead to poor adduction of the vocal folds and, therefore, increase the amount of random noise in the vocal note. 80 Tense/Pressed/Effortful/Strained Voice Sounds “effortful” Physiologic Longer closed phase Reduced airflow Potential Acoustics Change in harmonic (periodic) energy Flatter harmonic roll off 81 82 Roughness Perceptual Description Perceived cycle-to-cycle variability in voice Physiologic Factors Vocal folds vibrate, but in an irregular way Potential Acoustic Consequences Cycle-to-cycle variations F0 and amplitude Elevated jitter Elevated shimmer 83  Harmonics (signal)-to-noise-ratio (SNR/HNR) Index of BREATHINESS  HNR Relatively more signal Indicative of normality  HNR Relatively more noise (thus, disorder) Normative values depend on method of calculation “normal” HNR ~ 15 84 What are norms? Good source: Baken & Orlikoff (2000) 85  jitter: