Tutorials - Voice Production

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Principles of Voice Production

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Abduction quotient: The ratio of the glottal half-width at the vocal processes to the amplitude of vibration of the vocal fold

Absolute pressure: The pressure applied by fluid particles to adjacent particles or to the walls of the container; this pressure is always positive except in a perfect vacuum, where it is zero (measured in kPa)

Acceleration: The rate of change of velocity with respect to time (measured in m/s2)

Acoustic power: The physical measure of the amount of energy produced and radiated into the air per second (measured in watts)

Actin: A protein molecule that reacts with myosin to form an actomyosin, the contractile part of a myofilament

Abduct: To move apart, separate

Adduct: To bring together, approximate

Alveolar pressure: The pressure that is common to all of the alveoli in the lungs (measured in kPa)

Alveoli: Tiny airsacs within the lungs where the exchange of oxygen and carbon dioxide takes place

Amplitude: The maximum excursion from equilibrium in an oscillatory movement or waveform

Amplitude spectrum: A display of relative amplitude versus frequency of the sinusoidal components of a waveform

Amplitude to length ratio: The ratio of vibrational amplitude at the center of the vocal fold to the length of the vocal fold

Anatomy: The science of structure in organisms

Angular speed: The rate of change of angle with time in circular or sinusoidal motion

Anisotropic: Property of a material that produces different strains when identical stresses are applied in different directions

Antagonist (muscle): An opposing muscle

Anterior: Toward the front

Anterior commissure: The joining together of the vocal folds in the front of the larynx

Antinodes: The "peaks" in a standing wave pattern

Aperiodicity: The absence of periodicity; no portion of the waveform repeats exactly

Aphonia: The absence of vocal fold vibration; the inability to set the vocal folds into vibration

Arthritis: Inflammation of joints in the body; in particular, the cricoarytenoid joint

Arytenoid cartilages: Paired, pyramidal-shaped cartilages to which the vocal folds are attached

Aspiration: The sound made by turbulent airflow preceding or following vocal fold vibration, as in [ha] or [ah]

Atmospheric pressure: The absolute pressure of the atmosphere (measured in any convenient unit, e.g., 760 mmHg)

Atresia: Occlusion of the airway due to failure of the vocal folds to split apart

Atrophy: A wasting away of cells

Attractor: A trajectory in phase space


Bernoulli's Principle: If the energy in a confined fluid stream is constant, an increase in particle velocity must be accompanied by a decrease in pressure against the wall

Bifurcation: A sudden qualitative change in the behavior of a system

Bilateral vocal fold paralysis: Paralysis of the thyroarytenoid muscle in both vocal folds

Biomechanics: The study of the mechanics of biological tissue

Bleet: The result of nervousness or excessive physical tension, manifested by a fast vibrato, like the bleeting of a sheep

Body forces: Forces that act on all portions of a distributed mass

Bottleneck: A region in a singer's pitch range where a register change is mandatory

Boyle's law: In a soft-walled enclosure and at a constant temperature, pressure and volume are inversely related

Breathy voice: The result of a widened glottis with excessive airflow that produces air turbulence

Bronchioli: A tree-like structure of small ducts that connect the alveoli

Bronchitis: Inflammation of the bronchial tubes


Carrier:A waveform (typically a sinusoid) whose frequency or amplitude is modulated by a signal

Categorical perception: The perception of discrete entities in a physical continuum (like a finite number of colors in a rainbow)

Caudal: Toward the tail

Chaos: A qualitative description of a dynamical system that seems unpredictable

Component frequency: Mathematically, a sinusoid; perceptually, a pure tone. Also called partial.

Compression: A deformation of a body that decreases its entire volume

Compressional stress: A stress that points toward a surface, tending to squeeze an object

Condensation: An increase in density

Constitutive equation: The mathematical relation between an applied stress and the resulting strain

Constructive interference: The interference of two or more waves such that enhancement occurs

Contact ulcer: A lesion caused by irritation, such as acidic liquids or mechanical stress, on the vocal processes; usually acquired by people who have gastroesophageal reflux or speak with a pressed voice

Continuum mechanics: The mechanics of objects that are distributed continuously (in a macroscopic sense) over space (e.g., gases, liquids, solids)

Contraction: A decrease in the dimension of interest (i.e., length)

Convergent (glottal shape): The glottis narrows from bottom to top

Conversion aphonia: A symptom in which muscle activation patterns prevent the vocal folds from being set into vibration; caused by extreme emotional distress, hysteria

Corner vowels: [a], [i] and [u]; vowels at the corners of a vowel triangle; they necessitate extreme placements of the tongue

Creaky voice: The perceptual result of subharmonic or chaotic patterns in the glottal waveform; if a subharmonic is below about 70 Hz, creaky voice may be perceived as pulse register

Cricoid cartilage: A solid ring of cartilage that completely surrounds the laryngeal airway, located directly below the thyroid cartilage

Cricothyroid muscle: An intrinsic laryngeal muscle that is used primarily to control pitch (paired)

Crossover frequency: The fundamental frequency for which there is an equal probability for perception of two adjacent registers

Croup: A respiratory disorder brought about by tissue swelling in the subglottal airway, creating a severe constriction

Cycle: A 360o rotation; same as a period in periodic motion

Cysts: Benign, sac-like lesions with a hardened core


Damp:To diminish, or attenuate an oscillation

Deformation: The result of stress applied to any surface of a continuous medium, unless the medium is infinitely stiff. Examples are elongation, compression, contraction, or shear .

Dehydration: A condition in which the body is deprived of fluids, possibly affecting the viscous and elastic properties of the vocal folds

Destructive interference: The interference of two or more waves such that full or partial cancellation occurs

Diaphragm: A large, dome-shaped structure at the bottom of the ribcage that separates the lungs from the viscera; it is composed of a sheet of muscle and tendon

Differential control (of muscles): Gradual release of a muscle with concomitant gradual contraction of an antagonist muscle

Displacement: The distance between two points in space, including the direction from one point to the other

Displacement flow: Air in the glottis that is squeezed out when the vocal folds come together

Divergent (glottal shape): The glottis widens from bottom to top

Do di petto (Italian): "C in chest"

Dorsal: Toward the back

Dynamics: A branch of mechanics that deals with the study of forces that accelerate object(s)

Dystrophy: A malfunctioning of cells


Edema: Excessive accumulation of fluid in tissues, causing a "puffing up" or "bloating" effect. Although edema does not necessarily impede vocal fold vibration, it may add a crackly, noisy component to the voice.

Elastic recoil pressure: The alveolar pressure derived from extended (strained) tissue in the lungs, ribcage, and the entire thorax after inspiration (measured in Pascals)

Electroglottogram: A display of the time-varying electrical conductance through the larynx in the glottal region

Elongation: An increase in one dimension of interest (i.e., length)

Epiglottis: A flap of cartilage that seals the entry-way to the larynx during swallowing and opens the entry-way during breathing

Ergometrics: Engineering principles of machines applied to the human body

Expansion: A deformation of a body such that the entire volume increases

External forces: Forces imposed on all parts of a material by outside influences (e.g., the earth's gravity)


Fach (German): Literal meaning, job specialty

Fibrosis: Cross-linking between parallel strands (fibers) in a reparative or reactive process, creating an excess amount of fibers

Flow: The volume of fluid passing through a given cross-section of a transport system (e.g., a tube or a duct) per second; also called volume velocity (measured in liters per second)

Flow resistance: The ratio of pressure to flow (measured in kPa-s/l)

Fluctuation: A severe deviation from an expected pattern or constant

Fluid: A substance that is either a liquid or a gas

Fluid mechanics: The study of motion or deformation of liquids and gases

Flutter: Modulation in the 10-12 Hz range

Force: A push or pull; the physical quantity imparted to an object to change its momentum

Forced oscillation: Oscillation imposed on a system by an external source

Formant: A resonance of the vocal tract

Formant bandwidth: The difference in frequency between the two half-power points on the slopes of a resonance curve

Formant tuning: A boosting of vocal intensity when Fo or one of its harmonics coincides exactly with a formant frequency

Free-body diagram: A diagram in which all natural attachments and influences of the environment are replaced by equivalent forces acting on the body

Fricatives: Speech sounds produced by turbulence in a constriction of the vocal tract, such as an "s" produced with the teeth

Frontal (or coronal) plane: An anatomical plane that divides the body into anterior and posterior portions; across the crown of the head

Functional vocal disorder: A disorder for which there is no identifiable lesion, but the larynx functions abnormally and the voice sounds abnormal

Fundamental Frequency (Fo): The lowest frequency in a periodic waveform; also called the first harmonic frequency


Gas: A substance that preserves neither shape nor volume when acted upon by forces, but adapts readily to the size and shape of its container

Gastroesophageal reflux: The spilling of digestive acids onto laryngeal tissues, causing irritation

Geometry: The science of describing and measuring objects in space

Glottal resistance: The pressure across the glottis divided by the flow through the glottis

Glottal stop (or click): A transient sound caused by the sudden onset or offset of phonation

Glottis: The airspace between the vocal folds

Granuloma: A large, grainy-surfaced growth, often caused by prolonged intubation


Half-power frequencies: The two frequencies on opposite sides of a resonant peak (or pass-band) where the power transmitted by a filter is one half of its value at the peak

Harmonic: Equally spaced in frequency; a component whose frequency is an integer multiple of the fundamental

Hemorrhage (of the vocal fold): Rupture of one or more blood vessels in vocal fold tissues

Hooke's Law: Stress is proportional to strain; or, in simpler form, force is proportional to elongation

Hyoid bone: A horseshoe-shaped bone that "floats" above the larynx and serves as a connecting post to the tongue, velum, etc.


In vivo: In the living body

In vitro: Outside the living body; for example, in excised tissue, in a test tube, or on the lab bench

Incompressibility: Property of a substance that conserves volume in a deformation

Inertia: Sluggishness; a property that resists a change in its momentum

Inferior: Below

Infrahyoid muscle group: One of the two extrinsic muscle groups that includes the sternohyoid, the sternothyroid, the omohyoid and the thyrohyoid muscles

Intensity: A measure of power per unit area

Interarytenoid muscle: An intrinsic laryngeal muscle that connects the two arytenoid cartilages

Internal forces: Forces due to interactions (e.g., collisions) between particles of a substance

Inverse filtering: A technique used to study the sound source at the glottis. Ideally, this technique removes the filtering effect of the vocal tract on the glottal source. The purpose isto study the source or the vocal tract in isolation, although there are both practical and theoretical limitations.

Inverse square law: Sound intensity is inversely proportional to the square of the distance from the sound source

Isometric: Constant geometric shape during a muscle contraction; more specifically, constant length


Jitter: Short-term (cycle-to-cycle) variability in fundamental frequency

Juvenile papillomatosis: A disease characterized by the clustering of many papillomas (small blister-like growths) over the vocal folds, and elsewhere in the larynx and trachea


Keratosis: A build-up of keratin (a tough, fibrous protein) on the surface of the vocal folds

Kinematics: The study of movement without reference to forces

Kinetic energy: The energy of matter in motion (measured in joules)

Kinetics: The study of movement as a consequence of known or assumed forces


Laminar: Smooth or layered; in fluid mechanics, indicating parallel flow lines

Laryngeal web: A web between the vocal folds; in particular, failure of the vocal folds to split during fetal development

Laryngectomy: Removal of the larynx; may be conservative (larynx is partially removed) or radical (entire larynx is removed)

Laryngitis: Inflammation of laryngeal tissues

Laryngocele: An enlargement of the ventricular space between the false folds and the true folds

Laryngomalacia: A condition in which the epiglottis is abnormally shaped, constricting the supraglottal airway

Larynx: An organ of the body, situated in the neck, that houses the vocal folds

Lateral cricoarytenoid muscle: An intrinsic laryngeal muscle that brings together the vocal processes by rotation and forward rocking of the arytenoids on the cricoarytenoid joint (paired)

Lateral: Toward the outside (away from the center)

Leukoplakia: A white, patchy membrane on the vocal folds caused by chronic irritation

Lift: A transition point along a pitch scale where vocal production becomes easier

Line spectrum: A spectrum that contains discrete (line) frequencies only

Liquid: A substance that assumes the shape of its container, but preserves its volume

Loft: A suggested term for the highest (loftiest) register: usually referred to as falsetto voice

Lombard effect: The adjustment of vocal loudness according to the level of auditory stimulation, particularly in noisy environments

Longitudinal: Along a natural direction (e.g., in the direction of tissue fibers, or in the direction of airflow)

Loudness: The amount of sound perceived by a listener; a perceptual quantity that can only be assessed with an auditory system


Macroscopic: Viewing on a larger scale; on a macroscopic scale, a material is considered homogeneous rather than molecular

MAP: Muscle Activation Plot, particularly for the cricothyroid and thyroarytenoid muscles in Fo control

Mean squared error: The squared difference between the actual values and the expected values of a data set, averaged over the number of values

Mechanical equilibrium: The state in which all forces acting on a body cancel each other out, leaving a zero net force in all directions

Mechanics: The study of objects in motion and the forces that produce the motion

Medial (or mesial): Toward the center (midline or midplane)

Messa di voce (Italian): Placing of the voice; singing a crescendo-decrescendo with a well-placed voice

Microscopic: Viewing on a small scale; in physics, typically at the molecular level

Middle (or mixed) voice: The mixture between chest voice and falsetto; another term for "head" voice in singing

Modulation: The systematic change of a cyclic parameter, such as amplitude or frequency

Momentum: Mass times velocity; a quantity that determines the potential force that an object can impart to another object by collision

Motor unit: A group of muscle fibers and the single motor nerve that activates the fibers

Mucocele: A benign sac-like lesion with a liquid core

Muscle fascicles: Groups of muscle fibers enclosed by a sheath of connective tissue

Muscle fiber: A long, thin cell; the basic unit of a muscle that is excited by a nerve ending

Muscular tension dysphonia: Excessive longitudinal tensions or prephonatory positioning that impedes vibration of the vocal folds

Mutational dysphonia: A voice disorder in which vocal pitch and general pattern of vibration of vocal folds, assume characteristics of the opposite gender

Myofibril: A subdivision of a muscle fiber; composed by a number of myofilaments

Myofilament: A microstructure of periodically-arranged actin and myosin molecules; a subdivision of a myofibril

Myosin: A protein molecule that reacts with actin to form actomyosin, the contractile part of a myofilament


Natural oscillation: Oscillation without imposed driving forces

Neutral equilibrium: The state in which a disturbance may cause a body to be displaced from its rest position, but left alone the body is neither accelerated toward nor away from the original position

Nodes: The "valleys" in a standing wave pattern, where pressure or displacement is minimum

Nodule: A growth on the surface of the vocal fold, believed to be caused by repeated and prolonged collision between the tissue of opposing vocal folds


Organic voice disorder: Disorders for which a specific lesion is identified in the larynx or elsewhere in the body

Oscillation: A repeated back and forth movement

Ossify: Turn to bone


Papillomas: Small benign epithelial tumors that my appear randomly or in clusters on the vocal folds, larynx and trachea

Parietal pleura: The outermost of two membranes surrounding the lungs

Particle mechanics: The mechanics of objects that occupy essentially no space (point masses)

Particle: A finite mass with zero dimensions, located at a single point in space

Pascal (Pa): International standard unit of pressure; one newton (N) per meter squared (m2)

Pascal's Law: Pressure is transmitted rapidly and uniformly throughout an enclosed fluid at rest

Pass band: A band of frequencies minimally affected by a filter; it is the high flat region in a filter spectrum

Passaggi (Italian): Passages on a pitch scale where the voice tends to change register involuntarily

Passive stress: The stress caused by straining (typically elongating) non-muscular tissue or non-activated muscular tissue

Pear-shape-down paradigm: A breath support technique in which ribcage is free to move, and pressure is exerted downward toward the pelvis and outward toward the abdomen

Pear-shape-up paradigm: A breath support technique in which the ribcage is kept high and stable and the diaphragm and abdomen are used primarily to pump the air

Period: The time interval between repeating events

Periodic: Repeating over and over again; having a period

Perturbation: A minor disturbance, or small change, from an expected behavior

Pharynx: The airway in the neck above the larynx and below the velum

Phase: 1) The manner in which molecules are arranged in a material, i.e., as a gas, liquid, or solid; 2) the angular separation between two events on periodic waveforms

Phase space: A space created by two or more independent dynamical variables, such as positions and velocities, to plot the trajectory of a moving object

Phase spectrum: A display of the relative phases versus frequency of the components of a waveform

Phonetogram: Alternate term for Voice Range Profile

Pitch: A perception of how high versus low in a sound

Pleural space: The fluid-filled space between the parietal and visceral pleura

Plosive: A transient speech sound generated by the sudden onset or offset of air movement in the vocal tract

Point of origin: In anatomy, where a muscle or other soft tissue begins

Point of insertion: In anatomy, where a muscle or other soft tissue ends

Polyp: An edemic growth, brought about by irritation of the epithelium. Specific types of polyps are: sessile, pedunculated, and polypocorditis

Posterior cricoarytenoid muscle: An intrinsic laryngeal muscle that is the primary abductor of the vocal folds (paired)

Posterior: Toward the back

Power: The rate of delivery (or expenditure) of energy (measured in watts)

Pressed voice: The result of a constricted glottis with insufficient airflow

Pressure: Force per unit area; more precisely, the magnitude of a compressional stress (measured in kPa)

Primo passaggio (Italian): "The first passage"; the first register change perceived in a voice

Pulmonary system: The interrelated group of body structures that includes the lungs and the respiratory airways


Quasiperiodic: An imprecise term sometimes used to suggest a small deviation from periodicity


Radian: The angular measure obtained when the arc along the circumference of the circle is equal to the radius

Radian frequency: The number of radians per second covered in circular or sinusoidal motion

Rarefaction: A decrease in density

Reflection coefficient: A fraction of the incident wave that is reflected

Registers: Perceptually distinct regions of vocal quality as pitch or loudness is changed

Relative pressure: The change in pressure above or below absolute pressure; also called gauge pressure (measured in kPa)

Resonance: Reinforced natural oscillation; literally, a resounding by echoes or other types of enhancement

Restoring force: A force that brings an object back to a stable equilibrium position

Rostral: Toward the mouth (beak)


Sagittal: An anatomical plane that divides the body into left and right sides

Sarcoplasmic reticulum: Connective tissue enveloping groups of muscle fibers

Scalar: A quantity that scales, or adjusts size; a single number

Secondo passaggio (Italian): "The second passage"; the second register change perceived in a voice

Self-sustained oscillation: An oscillation that continues indefinitely without an external driving force; since the net energy loss per cycle must be zero, self-oscillation requires an internal energy source

Shear stress: A stress applied tangential to a surface

Shimmer: Short-term (cycle-to-cycle) variability in amplitude

Simple harmonic motion: Sinusoidal motion; the smoothest back and forth motion possible

Singing registers: Chest, head, falsetto, whistle

Sinus of Morgagni: Another name for the laryngeal ventricle; an airspace between the true and false vocal folds

Sinusoid: A graph representing the sine or cosine of a constantly increasing angle; the smoothest and simplest back and forth movement, characterized by a single frequency, an amplitude, and a phase

Sinusoidal motion: The projection of circular motion (in a plane) at constant speed onto one axis in the plane

Solid: A substance which maintains its shape, independent of the shape of its container

Solid mechanics: The mechanics of solid objects, those that move but do not easily deform

Sound propagation: The process of imparting a pressure or density disturbance to adjacent parts of a continuous medium, creating new disturbances at points further away from the initial disturbance

Source-filter theory: A theory that assumes the time-varying glottal airflow to be the primary sound source and the vocal tract to be an acoustic filter of the glottal source

Spasmodic dysphonia: A poorly-understood disorder characterized by intermittent phonation with a strained-strangled production; may be of the adductor or abductor type

Speaking registers: Pulse, modal and falsetto

Spectral slope: A measure of how rapidly energy decreases with increasing frequency, or, for periodic waveforms, with increasing harmonic number

Spectral slope transition: An abrupt voice quality change that results from an abrupt acoustic change, specifically from sudden loss or gain of high frequency sound energy at the source

Spectrum: Short for "spectrum of frequencies": a display of relative magnitudes or phases of the component frequencies of a waveform

Speed: The rate of change of distance with time; the magnitude of velocity

Stable equilibrium: A unique state to which a system with a restoring force will return after it has been displaced from rest

Standard deviation: The square root of the variance

Standing wave: A wave that appears to be standing still; it occurs when waves with the same frequency (and wavelength) moving in opposite directions interfere with each other

Statics: A branch of mechanics that deals with the study of objects in equilibrium (where there is no acceleration)

Stop band: A band of frequencies rejected by a filter; it is the low region in a filter spectrum

Strain: Deformation relative to a rest dimension, including direction (e.g., elongation per unit length)

Strain creep: A continuous deformation (e.g., elongation) under constant applied stress

Strain rate: The rate of change of strain with respect to time

Stress: Force per unit area, including the direction in which the force is applied to the area

Stress relaxation: Reduction of tissue stress over time at constant length

Strohbass (German): "Straw bass"; another term for pulse register

Subglottal: Below the glottis

Subharmonic: A component of a waveform whose frequency is an integer fraction of the fundamental (e.g., 1/2, 1/3, 1/4,. . .)

Sulcus (vocalis): A furrow or groove in the vocal fold, particularly on the medial surface

Superior: Above

Supraglottal: Above the glottis

Suprahyoid muscle group: One of the two extrinsic muscle groups that includes the stylohyoid muscle, anterior and posterior bellies of the digastric muscle, geniohyoid, the hyoglossus and mylohyoid

Surface forces: Forces that act only on the surface of a distributed mass


Temporal gap transition: The transition from a continuous sound to a series of pulses in the perception of vocal registers

Tensile stress: A stress that points away from a surface, tending to pull an object apart

Tessitura (Italian): Texture; the average pitch level of a song or part of a song in relation to the overall range of the instrument

Testosterone: The hormone responsible for development of male sexual characteristics, which includes major growth in the larynx

Thorax: The part of the body between the neck and abdomen

Three-layer scheme (of vocal fold tissues): A description of the tissues of the vocal fold inwhich the mucosa consists of the epithelium and the superficial layer of the lamina propria, the ligament consists of the intermediate and deep layers of the lamina propria, and muscle refers to the thyroarytenoid muscle

Thyroarytenoid muscle: An intrinsic laryngeal muscle that comprises the bulk of the vocal fold (paired)

Thyroid cartilage: The largest cartilage of the larynx; it is comprised of two plates joined anteriorly at the midline. It's anterior prominence is called the "Adam's apple"

Tidal volume: The amount of air breathed in and out during respiration (measured in liters)

Timbre: The quality given to a sound by its overtones

Tracheal stenosis: A constricted region in the trachea

Tracheoesophageal fistula: A congenital condition in which a hole is present between the trachea and the esophagus

Transglottal flow: Air that is forced through the glottis by a transglottal pressure

Transverse: 1) Referring to an anatomical plane that divides the body crosswise, or 2) a characterization of direction, indicating "perpendicular to the fibers or flow"

Tremor: Modulation in the 4-6 Hz range

Trill: A deliberate attempt to alternate rapidly between a base note and an adjacent higher note; a musical ornament

Trillo (Italian): Originally a trill, but in recent pedagogy a rapid repetition of the same note, which usually includes repeated voice onset and offset

Turbulence: Irregular movement of air, similar to white water which usually causes a hissing sound

Two-layer scheme (of vocal fold tissues): A description of the tissues of the vocal fold in which the body is equivalent to the deep layer of the lamina propria and the muscle, while the term cover is used to describe the combination of epithelium, superficial, and intermediate layers of the lamina propria


Unilateral vocal fold paralysis: Paralysis of the thyroarytenoid muscle of one vocal fold

Unstable equilibrium: The state in which a disturbance of a mechanical system will cause a drift away from a rest position


Variability: The ability of someone or something to change, by design or by accident

Variance: The mean squared difference from the average value in a data set

Vector: A quantity made up of two or more independent items of information, always grouped together

Velocity: The rate of change of displacement with respect to time (measured in meters per second, with the appropriate direction)

Ventral: Toward the belly

Ventricular folds: The "false folds", situated just above the vocal folds

Ventricular phonation: An abnormal muscle pattern dysphonia associated with hyperactivity in the false fold region

Vibrato (Italian): An ornament in singing; typically, a 4-6 Hz undulation of pitch and intensity

Viscera: The midsection of the body containing the stomach and the intestines

Visceral pleura: The innermost of two membranes surrounding the lungs

Viscoelastic material: A material that exhibits characteristics of both elastic solids and viscous liquids (e.g., the vocal fold)

Viscosity: Property of a liquid that measures resistance to speed of deformation; more formally, the ratio of shear stress to the rate of chane of shear strain

Vital capacity: The maximum volume of air that can be exchanged by the lungs with the outside; it includes the expiratory reserve volume, tidal volume and inspiratory reserve volume (measured in liters)

Vocal fold stiffness: The ratio of the effective restoring force (in the medial-lateral direction) to the displacement (in the same direction)

Vocal folds: A paired system of tissue layers in the larynx that can vibrate to produce sound

Vocal fry: A register with perceived temporal gaps; also known as pulse register

Vocal tract: The airway between the glottis and the mouth; also called the upper respiratory tract

Vocal tract resonance: Constructive interference (reinforcement) of waves experiencing multiple reflections in the vocal tract

Voice Range Profile: A visual display of vocal intensity range versus fundamental frequency

Volume: "Amount of sound", best measured in terms of acoustic power or intensity

Volumetric strain: A change in volume divided by the unstressed volume


Wave impedance (acoustic): In a sound propagating medium, the ratio of acoustic pressure to the speed of air particles driven by this pressure

Waveform: A plot of any variable (e.g. pressure, flow, or displacement) changing as time progresses along the horizontal axis; also known as a time-series

Wavefront: The initial disturbance in a propagating wave

Whisper: Sound created by turbulent glottal airflow in the absence of vocal fold vibration

Whistle register: The highest of all registers (in pitch). It occurs in females, extending the pitch range beyond F6

Wobble: A slow vibrato resulting from a lack of excitement, poor muscle tone, or fatigue

Wow: Modulation in the 1-2 Hz range


Young's modulus: The ratio between the magnitudes of stress and strain
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