Phonation

Functions of the larynx 3 valves which:- Permit airflow in and out Prevent inflow of unwanted substances Expel through cough Create subglottic pressure to brace thorax Produce vocalisation Reflexes control all above except phonation Functions of the larynx (For subglottic pressure do hold chair and pull) Larynx is basically a series of three valves that can open and close (or constrict and widen) to accomplish the following: 1. Permit air to enter and exit the trachea to maintain the life-sustaining activity of respiration. 2. Prevent anything other than air from entering the lower airways. This function is obviously important to maintain the patency of the airways for respiration. This function of the larynx is accomplished by the first of the three valves composed of the epiglottis and the aryepiglottic muscles. Which allow closure at the laryngeal aditus and with the superior and anterior movement of the larynx the bolus is encourages into the opened pharynx and not the now slightly higher laynx. 3. Expel through cough reflex foreign body that may enter the laryngeal cavities. The preventive action described above is not foolproof. Unwanted particles sometimes do find their way into the laryngeal cavities triggering the cough reflex. The two other valves – one formed by the ventricular folds and the other by the vocal folds – adduct abruptly during exhalation building up subglottal pressure (air pressure underneath the vocal folds). When both valves abruptly open, the forcful expelling of air that escapes carries it the foreign particles. 4. The development of subglottal pressure in order to brace and stabilize the thorax for lifting, excretion and childbirth. Both ventricular and vocal folds may be involved in this function of the larynx. 5. Produce tone for vocalization (crying, laughing, cooing and other non-speech sounds) speech and singing i.e. phonation. Typically, only the vocal valve is involved in the production of the laryngeal tone. However, ventricular folds are also capable of producing what is perceived as a harsh, strained sound. Reflexes perform all functions except for speech and singing.

Valving for Speech Phonation occurs through the use of the intrinsic laryngeal muscles and the laws of physics. Glottis opened by posterior crico-arytenoid during unvoiced sounds Glottis closed by lateral cricoarytenoid and inter-arytenoids The rhythmic opening and closing of the glottis during phonation is accomplished through a set of intrinsic muscles of the larynx and by the laws of physics relating to flow of air. Intrinsic muscles are those that have both their attachments inside the larynx. Both membranous and cartilaginous portions of the vocal folds vibrate during phonation. The glottis is open (the vocal folds are held apart) during breathing and during the production of unvoiced sounds by the action of the paired posterior cricoarytenoid muscles. To produce voice, the vocal folds are adducted primarily by the action of the lateral cricoarytenoid muscle. The paired muscles arise from the sides of the cricoid and attach to the muscular processes of the respective arytenoids. They rock and slide the arytenoids together. In addition, two other muscles aid adduction. The unpaired intra- or transverse arytenoid glides the arytenoids together and the paired oblique arytenoids pull the tip of the arytenoids together.

Valving for Speech

Glottic Cycle Vocal cords together Build up subglottic pressure Vocal cords forced apart Air rushes through gap Reduced subglottic pressure Vocal cords slap back together Air from the neck of a balloon Variation in compliance and complexity of wave See it opens from back to front and closes from front to back Also see opening starts from underneath

Glottic Cycle

Glottic Cycle GO TO Movie General anatomy/vocal folds/female and male

Aerodynamic Myoelastic Theory Aerodynamic- air pressure and flow Myoelastic- Elasticity of vocalis- the muscle in the vocal cord and the vocal ligament.

Bernoulli principle- Aerodynamics

Myoelastics -stiffness Another muscular force is stiffness. If the vocal cords are stiff then they will give more resistance to the air. The effect is like the difference between punching a bag of water and a bag of molasses. There will be less movement in the molasses. Vocal cords may become stiffer through contraction, infection or swelling. Consider splat balls and normal rubber ball or Newton’s cradle Another muscular force is stiffness. If the vocal cords are stiff then they will give more resistance to the air. The effect is like the difference between punching a bag of water and a bag of molasses. There will be less movement in the molasses. Vocal cords may become stiffer through contraction, infection or swelling. Consider splat balls and normal rubber ball or Newton’s cradle  SEE MOVIE HIGH PITCH, General/pathology/hydration (pitch)

Periodicity A period is a complete and closing cycle. Cycles/second = Frequency = Pitch Regularity/Irregularity may occur in: Pitch = Jitter Amplitude = Shimmer (not singing shimmer Vibrato may be called a fluctuation as it is regular Middle C 256, 512 C6 in scientific pitch notation (1046.502 Hz) Not the same as a vocal Shimmer Often increased jitter and shimmer at the ends of the pitch range Hear as an interference to the clear note Vibrato may be called a fluctuation as it is regular

Brainstorm How is pitch controlled in instruments?

Pitch Control Theory is changing Three main variables Other factors Mass- cross sectional bulk Stiffness- longitudinal tension Length Other factors Nervous tension Lack auditory feedback Each point at a time Guess factors- although have handouts, also fatigue, illness, breathe support

Pitch Control Lydia’s assembly Movie Singing/use/norm commercial/rigid Singing/use/classical/flex video standard and slow OR Spg/use/normal actor

Cover, Transition Body Model Hirano Cover is epithelium Transition is the middle and deep layers of the lamina propria making the vocal ligament Body of vocal cord is vocalis muscle Body cover Model In basic physics we know that the natural frequency of an oscillator is related to the stiffness to mass ratio. Stiffness of the vocal cord is largely regulated by vocal cord length. As the fibres are stretched fibres in the passive layer stiffen. Note also that a contracted muscle (shortened) muscle may be tighter than a stretched or elongated one. As the cricothyroid CT contracts with the Thyroarytenoid TA inactive there is a lengthening of the vocal cord and the effective stiffness increases. This will cause a rise in Fundamental frequency F0.  Where TA contracts and CT is inactive the length of the vocal cords will decrease and there will be a reduction in stiffness of the cover and an increase in stiffness of the body of the vocal cords. Usually the stiffness of the cover dominates the effect assist is closer proximity to the glottis where the vibrations are of the largest amplitude. F0 will probably decrease.  Where CT and TA contract together so that the length is unchanged it is likely that F0 will increase slightly.  CT is generally considered the main controller of pitch, The influence of TA must not be ruled out especially in the differential diagnosis of problems. There will be differences in normal voices in the extent to which each is activated. Also it may be that as one is trained more the other is relatively inactivated. This is possible because 2 separate branches of the vagus nerve innervate the muscles.

Body and Cover Model TA by RLN CT by SLN  Stiffness may be altered by a number of biological factors such as foods, drugs, hormones, disease, infection or dehydration.  Titze p198 The CT works by contracting its 2 muscles, the pars recta which pulls the front of the thyroid cartilage down and the pars oblique which pulls it slightly forward. The extent of the action will also be dependent on the stability of the arytenoids.  Analogies to strings and rubber bands. Because of the non-compliance of a steel string a small change to the peg on a guitar for example gives rise to a big change in pitch. The vocal cords on the other hand need a bigger pull to make a change. If you try this with an elastic band you may find when you stretch it only a little the pitch may go down because the stretch does not overcome the length increase.   The stress in the cover of the vocal cord can also, in principle be increased, by the thinning of the effective cross section of closure. i.e. the contact area becomes thinned. This may occur in the changing to a lighter register such as falsetto. The change in thickness overcomes the increase in length, which also goes with this register. The movement of the cover is the mucosal wave, which is imperative to good vocal quality. A lesion, external irritation such as mucus of dryness or tethering from surgery will affect quality.

New models Epithelium Basement membrane Metabolically active Microvilli Catching mucous Basement membrane Boundary between epithelium and lamina propria Anchoring fibres (allow some gliding) and proteins such as hyaluronic acid

Properties of the vocal cords Stiffness mainly regulated by length Stretch and contracted muscle is also stiffer Vocal cords quite stretchy Wet slap due to compliance

Optimum Pitch The pitch created by the larynx in its neutral position Debate Larynx not move vertically to create this pitch Methods to achieve – Mmhmm Neutral counting i.e. the pitch at which any individual voice should be ideally placed. Not how some people have changes their pitch e.g. Mrs Thatcher, Tony Blair, David Beckham This has long been a topic for discussion – as to whether this really exists. When making a judgement about pitch loudness and timbre also affect the subjective judgement. If the pitch is appropriate then it draws little attention but if not it can reduce acceptability and intelligibility of the human voice. David Beckham, puberphonia   It makes sense that a non-stressful pitch will be one not at the extreme of the vocal range. Somewhere in the bottom 1/3 or ½ of Fo is likely to be the best. (Titze 1994) Consider also the voice immediately after getting out of bed compared with the voice midday or the voice after singing loudly to the radio or vocal exercise. Coleman and Markham 1991 in Titze measured this change. So perhaps the optimum pitch for each voice is not an absolute NB Pitch will decrease with a cold or if VC swollen. Will return when swelling reduced Movie Speaking/care/habitual pitch

Control of Vocal Intensity Increase in volume occurs with: Increased subglottic pressure Medial compression of the vocal cords Resistance to increased pressure by: Medial compression Tightness of abduction NB Trained singers may use less lung pressure to produce high volume Voices get louder with 1) increased subglottic pressure and 2) medial compression of the vocal folds. Consider the continuum of breathy voice to normal voice and from normal voice to pressed or harsh voice. Intensity increases reaches a peak and decreases again. Thus there appears to be a glottal setting when the intensity is maximised. In therapy it is often the case that the need is to re-establish the balance. Conversational speech has a sound pressure level (SPL) of about 60-65 decibels (dB) and shouting about 95 – 100dB when measures at 1 metre from the mouth. There is a direct relationship between subglottic pressure and the intensity of the voice. Resistance to increasing SPL is brought about mainly by medial compression and the tightness of adduction. Tight adduction is mainly due to the action of the transverse and oblique arytenoids. It seems that trained singers may use less lung pressure/effort to produce higher volumes than in untrained singers. (Titze and Sundberg 1992 Much of our control of volume is subconscious. An example is the Lombard effect, which is the adjustment of loudness according to the level of auditory stimulation. E.g. when someone speaks while listening to music on headphones talking louder than needed.  

Control of Vocal Intensity Show Movie Speaking/abuse/distance point out not good technique

Phonation onsets Glottal- closure before sound Breathy- air before sound Simultaneous.

Phonation types Thick vocal folds, Thin vocal folds Stiff vocal folds Speaking voice, Chest register Thin vocal folds Quiet voice, Head register Stiff vocal folds Falsetto Floppy vocal cords Creak - irregular vibration Thin cords for speaking no projection Creak thick and floppy no projection if tense becomes rough and strained