speech

/speech/, n.

1. the faculty or power of speaking; oral communication; ability to express one's thoughts and emotions by speech sounds and gesture: Losing her speech made her feel isolated from humanity.

2. the act of speaking: He expresses himself better in speech than in writing.

3. something that is spoken; an utterance, remark, or declaration: We waited for some speech that would indicate her true feelings.

4. a form of communication in spoken language, made by a speaker before an audience for a given purpose: a fiery speech.

5. any single utterance of an actor in the course of a play, motion picture, etc.

6. the form of utterance characteristic of a particular people or region; a language or dialect.

7. manner of speaking, as of a person: Your slovenly speech is holding back your career.

8. a field of study devoted to the theory and practice of oral communication.

9. Archaic. rumor.

[bef. 900; ME speche, OE spaec, var. of SPRAEC, deriv. of sprecan to SPEAK; c. G Sprache]

Syn. 1. parlance, parley, conversation, communication. SPEECH, LANGUAGE refer to the means of communication used by people. SPEECH is the expression of ideas and thoughts by means of articulate vocal sounds, or the faculty of thus expressing ideas and thoughts. LANGUAGE is a set of conventional signs, not necessarily articulate or even vocal (any set of signs, signals, or symbols that convey meaning, including written words, may be called language): a spoken language. Thus, LANGUAGE is the set of conventions, and SPEECH is the action of putting these to use: He couldn't understand the speech of the natives because it was in a foreign language. 3. observation, assertion, asseveration, comment, mention, talk. 4. talk, discourse.

SPEECH, ADDRESS, ORATION, HARANGUE are terms for a communication to an audience. SPEECH is the general word, with no implication of kind or length, or whether planned or not. An ADDRESS is a rather formal, planned speech, appropriate to a particular subject or occasion. An ORATION is a polished, rhetorical address, given usually on a notable occasion, that employs eloquence and studied methods of delivery. A HARANGUE is a violent, informal speech, often addressed to a casually assembled audience, and intended to arouse strong feeling (sometimes to lead to mob action). 6. tongue, patois.

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I

Human communication through audible language.

Speech sounds are made with air exhaled from the lungs, which passes between the vocal cords in the larynx and out through the vocal tract (pharynx and oral and nasal cavities). This airstream is shaped into different sounds by the articulators, mainly the tongue, palate, and lips (see articulation). Articulatory phonetics describes each sound in terms of the position and action of the articulators used to make it. Speech is also described in terms of syntax, lexicon (inventory of words or morphemes), and phonology (sounds).

II

(as used in expressions)

figure of speech

freedom of speech

speech act theory

speech recognition

speech synthesis

speech therapy

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▪ language

Introduction

      human communication through spoken language. Although many animals possess voices of various types and inflectional capabilities, human beings have learned to modulate their voices by articulating the laryngeal tones into audible oral speech.

The regulators

Respiratory mechanisms

      Human speech is served by a bellows-like respiratory activator, which furnishes the driving energy in the form of an airstream; a phonating sound generator in the larynx (low in the throat) to transform the energy; a sound-molding resonator in the pharynx (higher in the throat), where the individual voice pattern is shaped; and a speech-forming articulator in the oral cavity ( mouth). Normally, but not necessarily, the four structures function in close coordination. Audible speech without any voice is possible during toneless whisper; there can be phonation without oral articulation as in some aspects of yodeling (yodel) that depend on pharyngeal and laryngeal changes. Silent articulation without breath and voice may be used for lipreading.

      An early achievement in experimental phonetics at about the end of the 19th century was a description of the differences between quiet breathing and phonic (speaking) respiration. An individual typically breathes approximately 18 to 20 times per minute during rest and much more frequently during periods of strenuous effort. Quiet respiration at rest as well as deep respiration during physical exertion are characterized by symmetry and synchrony of inhalation (inspiration) and exhalation (expiration). Inspiration and expiration are equally long, equally deep, and transport the same amount of air during the same period of time, approximately half a litre (one pint) of air per breath at rest in most adults. Recordings (made with a device called a pneumograph) of respiratory movements during rest depict a curve in which peaks are followed by valleys in fairly regular alternation.

      Phonic respiration is different; inhalation is much deeper than it is during rest and much more rapid. After one takes this deep breath (one or two litres of air), phonic exhalation proceeds slowly and fairly regularly for as long as the spoken utterance lasts. Trained speakers and singers (singing) are able to phonate on one breath for at least 30 seconds, often for as much as 45 seconds, and exceptionally up to one minute. The period during which one can hold a tone on one breath with moderate effort is called the maximum phonation time; this potential depends on such factors as body physiology, state of health, age, body size, physical training, and the competence of the laryngeal voice generator—that is, the ability of the glottis (the vocal cords and the opening between them) to convert the moving energy of the breath stream into audible sound. A marked reduction in phonation time is characteristic of all the laryngeal diseases and disorders that weaken the precision of glottal closure, in which the cords (vocal folds) come close together, for phonation.

      Respiratory movements when one is awake and asleep, at rest and at work, silent and speaking are under constant regulation by the nervous system (nervous system, human). Specific respiratory centres within the brain stem regulate the details of respiratory mechanics according to the body needs of the moment. Conversely, the impact of emotions (emotion) is heard immediately in the manner in which respiration drives the phonic generator; the timid voice of fear, the barking voice of fury, the feeble monotony of melancholy, or the raucous vehemence during agitation are examples. Conversely, many organic diseases of the nervous system or of the breathing mechanism are projected in the sound of the sufferer's voice. Some forms of nervous system disease make the voice sound tremulous; the voice of the asthmatic sounds laboured and short winded; certain types of disease affecting a part of the brain called the cerebellum cause respiration to be forced and strained so that the voice becomes extremely low and grunting. Such observations have led to the traditional practice of prescribing that vocal education begin with exercises in proper breathing.

      The mechanism of phonic breathing involves three types of respiration: (1) predominantly pectoral breathing (chiefly by elevation of the chest), (2) predominantly abdominal breathing (through marked movements of the abdominal wall), (3) optimal combination of both (with widening of the lower chest). The female uses upper chest respiration predominantly, the male relies primarily on abdominal breathing. Many voice coaches stress the ideal of a mixture of pectoral (chest) and abdominal breathing for economy of movement. Any exaggeration of one particular breathing habit is impractical and may damage the voice.

brain functions

      The question of what the brain does to make the mouth speak or the hand write is still incompletely understood despite a rapidly growing number of studies by specialists in many sciences, including neurology, psychology, psycholinguistics, neurophysiology, aphasiology, speech pathology, cybernetics, and others. A basic understanding, however, has emerged from such study. In evolution, one of the oldest structures in the brain is the so-called limbic system, which evolved as part of the olfactory (smell) sense. It traverses both hemispheres in a front to back direction, connecting many vitally important brain centres as if it were a basic mainline for the distribution of energy and information. The limbic system involves the so-called reticular activating system (structures in the brain stem), which represents the chief brain mechanism of arousal, such as from sleep or from rest to activity. In man, all activities of thinking and moving (as expressed by speaking or writing) require the guidance of the brain cortex.

      In contrast to animals, man possesses several language centres in the dominant brain hemisphere (on the left side in a clearly right-handed person). It was previously believed that left-handers had their dominant hemisphere on the right side, but recent findings tend to show that many left-handed persons have the language centres more equally developed in both hemispheres or that the left side of the brain is indeed dominant. The foot of the third frontal convolution of the brain cortex, called Broca's area, is involved with motor elaboration of all movements for expressive language. Its destruction through disease or injury causes expressive aphasia, the inability to speak or write (see drawing). The posterior third of the upper temporal convolution represents Wernicke's area of receptive speech comprehension. Damage to this area produces receptive aphasia, the inability to understand what is spoken or written as if the patient had never known that language.

      Broca's area surrounds and serves to regulate the function of other brain parts that initiate the complex patterns of bodily movement (somatomotor function) necessary for the performance of a given motor act. Swallowing is an inborn reflex (present at birth) in the somatomotor area for mouth, throat, and larynx. From these cells in the motor cortex of the brain emerge fibres that connect eventually with the cranial and spinal nerves that control the muscles of oral speech.

      In the opposite direction, fibres from the inner ear have a first relay station in the so-called acoustic nuclei of the brain stem. From here the impulses from the ear ascend, via various regulating relay stations for the acoustic reflexes and directional hearing, to the cortical projection of the auditory fibres on the upper surface of the superior temporal convolution (on each side of the brain cortex). This is the cortical hearing centre where the effects of sound stimuli seem to become conscious and understandable. Surrounding this audito-sensory area of initial crude recognition, the inner and outer auditopsychic regions spread over the remainder of the temporal lobe of the brain, where sound signals of all kinds appear to be remembered, comprehended, and fully appreciated. Wernicke's area (the posterior part of the outer auditopsychic region) appears to be uniquely important for the comprehension of speech sounds.

      The integrity of these language areas in the cortex seems insufficient for the smooth production and reception of language. The cortical centres are interconnected with various subcortical areas (deeper within the brain) such as those for emotional integration in the thalamus and for the coordination of movements in the cerebellum (hindbrain).

      All creatures regulate their performance instantaneously comparing it with what it was intended to be through so-called feedback mechanisms involving the nervous system. Auditory feedback through the ear, for example, informs the speaker about the pitch, volume, and inflection of his voice, the accuracy of articulation, the selection of the appropriate words, and other audible features of his utterance. Another feedback system through the proprioceptive (proprioception) sense (represented by sensory structures within muscles, tendons, joints, and other moving parts) provides continual information on the position of these parts. Limitations of these systems curtail the quality of speech as observed in pathologic examples (deafness, paralysis, underdevelopment).

The structure of the larynx

      The morphology (structure) of the larynx is studied according to the cartilages (cartilage), muscles, nerves, blood vessels, and membranes of which it is composed.

Cartilages of the larynx

      The frame or skeleton of the larynx is composed of several cartilages, three single and three pairs. Single cartilages are the shield-shaped thyroid in front, whose prominence forms the “Adam's apple” in the male; the cricoid cartilage below, which resembles a signet ring and connects the thyroid to the trachea or windpipe; and the leaf-shaped epiglottis, or laryngeal lid, on top. Among the paired cartilages are the two arytenoids, which ride on the cricoid plate and move the vocal cords sideways; the two corniculate cartilages of Santorini on top of the arytenoids; and the two cuneiform cartilages of Wrisberg. The cartilages are held together by ligaments and membranes, particularly around their joints. The larynx is connected below to the uppermost ring of the trachea, while above it is connected by the thyrohyoid ligaments to the hyoid bone beneath the tongue. Most of the laryngeal cartilages ossify (turn to bone) to variable degrees with age under the influence of masculinizing hormones. This fact is an important sign in the X-ray diagnosis of certain vocal disorders. If a man shows less ossification than is normal for his age, he may be deficient in male hormones; this may also account for an effeminate sound in his voice. Conversely, when a woman shows increased laryngeal ossification, she may suffer from virilizing hormones, which might also explain any lowering and roughening in her voice.

Laryngeal muscles (muscle)

      There are two types of laryngeal muscles, the external (extrinsic) ones, which move the larynx as a whole, and the internal (intrinsic) ones, which move the vocal folds to shape the glottis. It is helpful to remember that the anatomical names of most such muscles are derived from their origin on one structure to their insertion on another.

      The extrinsic muscles comprise the thyropharyngeus, which extends from the posterior border of the thyroid cartilage to the pharyngeal constrictor muscle, and the cricopharyngeus, which extends from the cricoid cartilage to the lower portion of the pharynx and the opening of the esophagus (the food tube that connects the mouth and the stomach). This cricopharyngeus muscle aids in the closing of the esophagus whenever it is not open for swallowing. Under the influence of emotional tension, the cricopharyngeus muscle may go into a spasm, which leads to a painful sensation of tightening in the throat that is usually described as a “lump in the throat.” A disorder of this sort (which was previously referred to as globus hystericus) is now believed to be a sensation of cricopharyngeus spasm from emotional tension or imbalance as the result of excessive activity of the autonomic (involuntary) nervous system.

Extrinsic muscles

      Although it is situated outside the laryngeal cartilages, the short cricothyroid muscle, a triangular muscle between the respective two cartilages, is traditionally discussed among the intrinsic (internal) muscles. Whenever this muscle contracts, the cricoid and thyroid cartilages are brought together anteriorly. This moves the anterior (forward) insertion of the vocal cords inside the thyroid wing forward, while their posterior (backward) insertion on the arytenoid cartilages is shifted backward. From this rotation results a marked elongation of the vocal folds clearly visible on X-ray films. This stretching action is the chief mechanism for raising the pitch of the sound generated and thus for the differentiation of vocal registers (e.g., chest voice, falsetto). For embryologic reasons, the cricothyroid is the only laryngeal muscle that has its own nerve supply from the superior laryngeal nerve, a high branch of the vagus nerve (which issues from the brain stem). All other laryngeal muscles are innervated by the recurrent or inferior (low) laryngeal nerve, a low branch of the vagus nerve. This fact is important in the diagnosis of laryngeal paralysis because the resulting immobilization of the vocal cord and the remaining vocal function depend on the type of paralysis; i.e., whether only the high or the low nerve or both of the laryngeal nerves are paralyzed on one side.

Intrinsic muscles

      The intrinsic muscles include all of the following. The thyroarytenoid muscle extends from the inside of the anterior edge of the thyroid cartilage to the anterior vocal process of the arytenoid cartilage. This muscle may be separated into two portions, an internal part within the vocal cord and an external part between the vocal cord and the wing of the thyroid cartilage. For the most part, the fibres run parallel with the vocal cord. When they contract, they shorten the cord, make it thick, and round its edge. The external portion assists in bringing the vocal cords together, thus making glottal closure more tight.

      The cricoarytenoids are two muscle pairs: one lateral pair (to the side) and one posterior pair (backward). These two pairs of muscles have an antagonistic (opposing) action. The posterior cricoarytenoids are the muscles of inspiration that open the glottis. They arise from the posterior surface of the cricoid plate and are attached, in an upward, forward, and outward direction, to the lateral muscular process of the arytenoid cartilage. When these muscles contract, they rotate the arytenoid outward, thus opening the glottis. The lateral cricoarytenoids belong among the muscles of expiration, the adductor group. They arise from the lateral ring of the cricoid cartilage and insert into the muscular process of the arytenoid in an upward and backward direction. Contraction of the lateral cricoarytenoids rotates the arytenoid cartilages inward so that the vocal folds are brought together.

      The two sides of the interarytenoid muscle are blended into one single mass, which extends from the muscular process of one arytenoid to that of the other. The action of this muscle is to pull together the posterior aspect of the arytenoid cartilages, thus closing the posterior portion of the cartilaginous glottis between the vocal processes of the arytenoids.

      A fold from the top of the arytenoid to the lateral margin of the epiglottis on each side is supported by a bilateral band of muscle, the aryepiglotticus muscle. This semicircular structure aids in narrowing the laryngeal vestibule by pulling the arytenoids together and the epiglottis down. This is another example of the sphincter (sphincter muscle) action (“valve” function) of all adducting laryngeal muscles that bring the vocal cords together. This sphincter action, by tightening of its closure, is the basis for all laryngeal protection. When this primitive sphincter mechanism intrudes into the refined coordination of phonation, it constricts the voice and causes the throaty quality of retracted resonance. This primitive, protective mechanism is at the root of many functional voice disorders. Moreover, the constricting sphincter action by many muscles is very strong because it is opposed by only one muscle, the abducting posterior cricoarytenoid.

Vocal cords (vocal cord)

      The two true vocal cords (or folds) represent the chief mechanism of the larynx in its function as a valve for opening the airway for breathing and to close it during swallowing. The vocal cords are supported by the thyroarytenoid ligaments, which extend from the vocal process of the arytenoid cartilages forward to the inside angle of the thyroid wings. This anterior insertion occurs on two closely adjacent points, the anterior commissure. The thyroarytenoid ligament is composed of elastic fibres that support the medial or free margin of the vocal cords.

      The inner cavity of the larynx is covered by a continuous mucous membrane, which closely follows the outlines of all structures. Immediately above and slightly lateral to the vocal cords, the membrane expands into lateral excavations, one ventricle of Morgagni on each side. This recess opens anteriorly into a still smaller cavity, the laryngeal saccule or appendix. As the mucous membrane emerges again from the upper surface of each ventricle, it creates a second fold on each side—the ventricular fold, or false cord. These two ventricular folds are parallel to the vocal cords but slightly lateral to them so that the vocal cords remain uncovered when inspected with a mirror. The false cords close tightly during each sphincter action for swallowing; when this primitive mechanism is used for phonation, it causes the severe hoarseness of false-cord voice (ventricular dysphonia).

      The mucous membrane ascends on each side from the margins of the ventricular folds of the upper border of the laryngeal vestibule, forming the aryepiglottic folds. These folds extend from the apex of the arytenoids to the lateral margin of the epiglottis. Laterally from this ring enclosing the laryngeal vestibule, the mucous membrane descends downward to cover the upper-outer aspects of the larynx where the mucous membrane blends with the mucous lining of the piriform sinus of each side. These pear-shaped recesses mark the beginning of the entrance of the pharyngeal foodway into the esophagus.

      The mucous membrane of the larynx consists of respiratory epithelium made up of ciliated columnar cells. Ciliated cells are so named because they bear hairlike projections that continuously undulate upward toward the oral cavity, moving mucus and polluting substances out of the airways. The true vocal cords, however, are exceptional in that they are covered by stratified squamous epithelium (squamous cells are flat or scalelike) as found in the alimentary tract. The arrangement is functional, since the vocal cords have to bear considerable mechanical strain during their rapid vibration for phonation, which occurs during many hours of the day. The transition from the respiratory to the stratified epithelium above and below the vocal cords is marked by superior and inferior arcuate (arched) lines. Unfortunately, such transitional epithelium also has the drawback of being easily disturbed by chronic irritation, which is one reason why the large majority of laryngeal cancers (cancer) begin on the vocal cords. The mucous membrane of the larynx contains numerous mucous glands in all areas covered by respiratory epithelium, excepting again the vocal cords. These glands are especially numerous over the epiglottis and in the ventricles of Morgagni. The mucus secreted by these glands serves as a lubricant for the mucous membrane and prevents its drying in the constant airstream.

      The vocal cords also mark the division of the larynx into an upper and lower compartment. These divisions reflect the development of the larynx from several embryonal components called branchial arches (branchial arch). The supraglottic portion differs from the one beneath the vocal cords in that the upper portion is innervated sensorially by the superior laryngeal nerve and the lower (infraglottic) portion by the recurrent (or inferior) laryngeal nerve. The lymphatics (i.e., the vessels for the lymph flow) from the upper portion drain in an upward lateral direction, while the lower lymphatics drain in a lateral downward direction.

      The space between the vocal cords is called rima glottidis, glottal chink, or simply glottis (Greek for tongue). When the vocal cords are separated (abducted) for respiration, the glottis assumes a triangular shape with the apex at the anterior commissure. During phonation, the vocal cords are brought together (adducted or approximated), so that they lie more or less parallel to each other. The glottis is the origin of voice, although not in the form of a “fluttering tongue” as the Greeks believed.

      The vocal cords vary greatly in dimension, the variance depending on the size of the entire larynx, which in turn depends on age, sex, body size, and body type. Before puberty, the larynx of boys and girls is about equally small. During puberty (adolescence), the male larynx grows considerably under the influence of the male hormones so that eventually it is approximately one-third larger than the female larynx. The larynx and the vocal cords thus reflect body size. In tall, heavy males the vocal cords may be as long as 25 millimetres (one inch), representing the low-pitched instrument of a bass voice. A high-pitched tenor voice is produced by vocal cords of the same length as in a low-voiced female contralto. The highest female voices are produced by the shortest vocal cords (14 millimetres), which are not much longer than the infantile vocal cords before puberty (10–12 millimetres). The larynx is, among other things, a musical instrument that follows the physical laws of acoustics fairly closely.

Substitutes for the larynx

      A growing number of middle-aged or older patients have had their larynx removed (laryngectomy) because of cancer. Laryngectomy requires the suturing of the remaining trachea into a hole above the sternum (breastbone), creating a permanent tracheal stoma (or aperture) through which the air enters and leaves the lungs. The oral cavity is reconnected directly to the esophagus. Having lost his pulmonary activator (air from the lungs) and laryngeal sound generator, such an alaryngeal patient is without a voice (aphonic) and becomes effectively speechless; the faint smacking noises made by the remaining oral structures for articulation are practically unintelligible. This type of pseudo-whispering through buccal (mouth) speech is discouraged to help the patient later relearn useful speech on his own. A frequently successful method of rehabilitation for such alaryngeal aphonia is the development of what is called esophageal or belching voice.

Esophageal voice (pseudolaryngeal speech)

      Some European birds and other animals can produce a voice in which air is actively aspirated into the esophagus and then eructated (belched), as many people can do without practice. The sound generator is formed by the upper esophageal sphincter (the cricopharyngeus muscle in man). As a replacement for vocal cord function, the substitute esophageal voice is very low in pitch, usually about 60 cycles per second in humans. Training usually elevates this grunting pitch to about 80 or 100 cycles.

      Esophageal voice in man has been reported in the literature since at least 1841 when such a case was presented before the Academy of Sciences in Paris. After the perfection of the laryngectomy procedure at the end of the 19th century, systematic instruction in esophageal (belching) phonation was elaborated, and the principles of this vicarious phonation were explored. Laryngectomized persons in many countries often congregate socially in “Lost Cord Clubs” and exchange solutions of problems stemming from the alaryngeal condition.

Artificial larynx

      Approximately one-third of all laryngectomized persons are unable to learn esophageal phonation for various reasons, such as age, general health, hearing loss, illiteracy, linguistic barriers, rural residence, or other social reasons. These persons, however, can use an artificial larynx to substitute for the vocal carrier wave of articulation. Numerous mechanical and pneumatic models have been invented, but the modern electric larynx is most serviceable. It consists of a plastic case about the size of a flashlight, containing ordinary batteries, a buzzing sound source, and a vibrating head that is held against the throat to let the sound enter the pharynx through the skin. Ordinary articulation thus becomes easily audible and intelligible. Other models lead the sound waves through a tube into the mouth or are encased in a special upper dental plate. More recent efforts aim at surgically inserting an electric sound source directly into the neck tissues to produce a more natural sound resembling that of normal speech.

Theory of voice (vocalization) production

      The physical production of voice has been explained for a long time by the myoelastic or aerodynamic theory, as follows: when the vocal cords are brought into the closed position of phonation by the adducting muscles, a coordinated expiratory effort sets in. Air in the lungs, compressed by the expiratory effort, is driven upward through the trachea against the undersurface of the vocal cords. As soon as the subglottic pressure has risen sufficiently to overcome the closing effort of the vocal cords, the glottis is burst open, a puff of air escapes, the subglottic pressure is reduced, and the elasticity of the glottis together with the effect of the moving air causes the adducted cords to snap shut. The subglottic pressure rises again and the entire cycle is repeated. These cycles of exploding air puffs occur as frequently as the physical interaction of the subglottic pressure with the glottic resistance permits. The latter is determined by the tension of the vocal cords and their closing force. The number of these cycles per second is small for tones of low pitch and much greater for high tones, as will be explained later. The resulting laryngeal (larynx) fundamental tone thus varies greatly in audible pitch.

      According to the myoelastic theory, the production of laryngeal voice is a mechanical phenomenon directed by aerodynamic principles and muscular coordination. The vocal cords vibrate purely passively in the blowing airstream and are merely maintained in their position of phonation by the adducting muscles as these are activated by the laryngeal nerves. This vibration is not an active phenomenon like the whirring of the wings of a flying insect. Evidence for the myoelastic theory can be demonstrated in various ways. High-speed motion pictures of the vocal cords have been made, photographing their vibration at the rate of 4,000 or more frames per second. When such a picture is then projected at regular film speeds of 16 or 24 frames per second, the available film length is greatly extended in duration so that each of the hundreds of vocal-cord vibrations per second can be seen in ultraslow motion. A tone of 250 cycles per second (cps or Hz), for example, filmed at 4,000 frames and played back at 16 frames per second will permit each of the 250 vibrations to be seen for one second. Other evidence supporting the myoelastic theory is found in observations such as the fact that a nearly normal voice can be produced despite bilateral (on both sides) vocal-cord paralysis.

Vocal registers

The basic registers

      For many centuries the so-called vocal registers were well known to the classical masters of the bel canto style of singing, the basic registers being called chest voice, midvoice, and head voice. These terms are derived from observations, for example, that in the low-chest register the resonances are felt chiefly over the chest. When sitting on a wooden bench with a large male, one can feel the vibrations of his low voice being transmitted through the back of the bench. In the high head voice, the vibrations are felt chiefly over the skull. The practice of singing is based on several artistic subdivisions in both sexes, depending on factors as discussed below. Other vocal (vocal fry) phenomena may be heard below and above normal register limits, such as extra low tones, the “vocal fry.”

      The natural transition between two adjacent registers may be compared to the gearshift of a car. The same absolute vehicle speed can be maintained by driving either with the engine turning fast while in low gear or with fewer engine revolutions in the next higher gear. The register mechanism of the human voice is quite similar in this respect. Where the registers overlap, a series of transitional tones may be sung with either ofthe adjacent registers. These tones of the same fundamental frequency, sound level, and basic sound category in different vocal registers have recently been defined as isoparametric tones. In the untrained male voice, the transition between the midvoice and the high falsetto sounds abrupt; this so-called register break is similar to the noisy gearshift in a run-down truck. One aim of vocal education is to teach smoothly equalized register transitions.

      Loud phonation of any given tone shifts its register mechanism toward the next lower register; for example, a crescendo falsetto tone grows into loud head voice. Conversely, soft intonation raises the mechanism to the next higher type, as when a loud head tone fades into soft falsetto. This phenomenon is the physiologic basis of messa di voce, the technique of swelling tones. Thus, the characteristic mechanism of each register represents a continuum of intralaryngeal adjustments. In the male voice, the gradual and overlapping transitions of phonic function may be aligned as follows: low chest tones, loud–soft; transition; middle register, loud–soft; transition; loud head voice–soft artistic falsetto–thin natural falsetto. X-ray studies can show the difference between the loud male head voice and the soft male falsetto. The former employs the midvoice mechanism, the latter the falsetto mechanism. In the female voice, the two lower registers behave similarly, while head voice can be only loud or soft and may be followed by a fourth register, the flageolet or whistle register of the highest coloratura sopranos. The Italian term falsetto simply means false soprano, as in a castrato (castrated) singer. Hence, the normal female cannot have a falsetto voice.

Studies of register differences

      Studies devoted to the problem of voice register may be divided into two groups: observations of the visible laryngeal mechanism and studies of the audible register differences.

      Studies of the visible laryngeal mechanism for the production of different registers began with the laryngoscope. Modern laryngostroboscopes employ the oscillating light of a high-power fluorescent light source that is monitored by the laryngeal vibrations through a throat microphone. Such devices, when they flash on and off at just the right rate, make the vocal cord movements appear much slower than they actually are, so that the observer perceives a slow-motion pattern. High-speed cinematography (moviemaking) has elucidated many details of vocal cord function for the various registers. Radioscopic ( X-ray) methods were introduced only a few years after the discovery of X-rays in 1895. Among these, lateral (from the side) radioscopy of the larynx reveals the mechanism of vocal cord tension; frontal X-ray films demonstrate the typical configuration of the vocal cords for each register. Mechanical recordings of the respiratory movements of the chest, originally with rubber belts and lately with electronic strain gauges, disclose the breathing patterns for the various registers. Breath support (appoggio) of singing instruction can be demonstrated through such recordings, as well as by radiography of the chest. Aerodynamic measurements of pressure, flow rate, and volume of the air exhaled during specific phonic tasks have produced additional details. electromyography (study of muscle currents) involving the insertion of needle electrodes into certain laryngeal muscles permits the isolated recording of finely coordinated muscular effort during the singing in various registers.

      A second group of investigations concerns audible register differences as an acoustic phenomenon. Electroacoustic analysis demonstrates the specific sound-wave patterns (harmonic spectra) of each register. In general, the full chest voice is rich in higher harmonics, whereas the thin falsetto voice is composed chiefly of sound-wave energy distribution near the vocal fundamental (the relatively narrow band of wave frequencies that characterizes any particular voice). The subjective impressions of singers during the production of an ascending scale reflect the voluntary techniques of vocal breath control, such as with respiratory support (appoggio). Positioning of the larynx, suitable shaping of the pharyngo-oral resonator (vocal tract), proper placement of the tongue, and the specific tension of the soft palate belong among the learned techniques of register equalization. Definite vibrations (sound) may be felt in the thorax, in the area of the hard palate, or above the nose. These subjectively felt resonances depend on bone conduction of the laryngeal sound. Very little has as yet been done regarding the subjective evaluation of voice registers by listening judges. These perceptual factors are still little understood, but it appears that multiple acoustic perceptions operate in voice-register judgment.

      It is clear that the vocal registers represent a continuum of laryngeal adjustments in response to different respiratory-mechanical requirements necessary for the production of the individual frequency range. The poles of these adjustments at the opposites of chest voice and male falsetto voice illustrate the chief differences; the midvoice occupies an intermediate position.

Vocal attributes

Vocal frequency

      The voice has various attributes; these are chiefly frequency, harmonic structure, and intensity. The immediate result of vocal cord vibration is the fundamental tone of the voice, which determines its pitch. In physical terms, the frequency of vibration as the foremost vocal attribute corresponds to the number of air puffs per second, counted as cycles per second (cps or Hz). This frequency is determined by both stable and variable factors. The stable determinants of the individual voice range depend on the laryngeal dimensions as related to sex, age, and body type. The smaller a larynx, the higher its pitch range. Within this individually fixed range, variables that influence the pitch of a given phonation include: tension of the cord, force of glottal closure indicated by the glottal resistance, and expiratory air pressure. Growing tension of the cricothyroid muscle (as the external vocal cord tensor) increases the vocal pitch, and vice-versa. Increased glottal closure and expiratory effort add to this tensing effect under certain circumstances. For example, 100 vibrations per second produce a low chest tone of a low male voice, while 1,000 are close to the “high C” of a female soprano. An average vocal range normally encompasses two musical octaves (e.g., 100 to 400 vibrations per second); trained singers may reach three or more octaves.

Voice types

      Musical practice for centuries has recognized six basic voice types: bass, baritone, and tenor in the male, in contrast to contralto, mezzo-soprano, and soprano in the female. Sex, therefore, is one of the first determinants of voice type in the two categories. Body type and general physical constitution represent the second determinant of the individual voice type because the laryngeal dimensions vary in fairly strict conformity to whether the body type is large or husky or frail or small. A tall, athletic male usually has a large, spacious larynx. Repeated observations show that short, dainty females tend to have a small and delicately built larynx. The intermediate voice types of the male baritone and the female mezzo-soprano usually represent the corresponding intermediate body types. The art of singing recognizes additional subdivisions. The voice of a basso profundo is extremely low and heavy. The lyric tenor possesses a high, light, and flexible voice. Still higher and lighter is the counter tenor (as used in singing oratorios) who is the male counterpart of the highest female voice found in the extra high and light coloratura soprano. The dramatic voices employed in the Wagnerian operas represent intermediate forms between a male tenor (or high baritone) and a heroically masculine body type. The female dramatic soprano is usually heavily built; her strong mezzo-soprano voice can produce the high soprano tones.

      The registers are related to voice types. As a general rule, the low voices possess a large range of chest voice with a much smaller range of head voice. The reverse holds for the high voice types, while baritone and mezzo-soprano assume an intermediate position. In the normal individual and the well-trained singer in particular, the midvoice encompasses one musical octave. As a further rule of thumb, the traditional and optimal transition tones follow a fairly stable and general pattern.The three female voice types usually show the first transition from chest to midvoice at the tones d¹, e¹, and f¹, above middle c¹, respectively. The second transition between midvoice and head register in the three female voice types is almost precisely one octave higher. An extra-low contralto voice may prefer to shift the two transitions at slightly lower frequencies, whereas a very high coloratura soprano may prefer the two shifts a semitone (halftone) higher. The two transition tones of the three male voice types are situated almost precisely one octave lower than the respective six female transition tones. It should not be overlooked that the specific features in male voices sound approximately one octave lower than in the female voices of corresponding type. This octave phenomenon stems from the larger dimension of the adult male larynx. (The musical custom of writing the tenor part on the soprano stave in contrast to the correct notation of bass and baritone in the bass clef is a misleading tradition that derives from an old custom of four-part writing, for the tenor always sounds one octave lower than the soprano.)

Vocal ranges

      The individual ranges of the singing voice extend from about 80 cycles per second in the low bass to about 1,050 cycles per second in the “high C” of the soprano (all values are approximated). The lowest note of serious musical literature is a low B-flat with 58 cycles per second, used in bars 473, 475, 477, and 632 of the bass voice of the chorus in the fifth movement of Gustave Mahler's Symphony No. 2 (Resurrection). The highest is a high f³ with almost 1,400 cycles per second sung by the Queen of the Night in Mozart's Magic Flute. Exceptionally high soprano tones are no longer sung with vocal cord vibration but are produced in the flageolet (or whistle) register simply by whistling through the narrow elliptical slit between the overtensed and motionless vocal cords. When citing the exceptional vocalistic feats of singers from the classical bel canto era, it should not be overlooked that musical pitch has been rising markedly since those days. Concert pitch is presently standardized at 440 cycles per second for the international tuning tone a¹. In the last half of the 18th century, the reference tone was at least one semitone lower.

Harmonic structure

      A second attribute of vocal sound, harmonic structure, depends on the wave form produced by the vibrating vocal cords. Like any musical instrument, the human voice is not a pure tone (as produced by a tuning fork); rather, it is composed of a fundamental tone (overtone) (or frequency of vibration) and a series of higher frequencies called upper harmonics, usually corresponding to a simple mathematical ratio of harmonics, which is 1:2:3:4:5, etc. Thus, if a vocal fundamental has a frequency of 100 cycles per second, the second harmonic will be at 200, the third at 300, and so on. As long as the harmonics are precise multiples of the fundamental, the voice will sound clear and pleasant. If nonharmonic components are added (giving an irregular ratio), increasing degrees of roughness, harshness, or hoarseness will be perceived in relation to the intensity of the noise components in the frequency spectrum.

      The primary laryngeal tone composed of its fundamental and harmonics is radiated into the supraglottic vocal tract (above the glottis). The cavities formed by the pharynx, nasopharynx, nose, and oral cavity represent resonators. Since they are variable in size and shape through the movements of the pharyngeal musculature, the palatal valve, and the tongue in particular, the individual sizes of the supraglottic resonating chambers can be varied in countless degrees. The shaping of the vocal tract thus determines the modulation of the voice through resonance and damping. As a general rule, a long and wide vocal tract enhances the lower harmonics, producing a full, dark, and resonant voice. Conversely, shortening and narrowing of the vocal tract leads to higher resonances with lightening of the voice and the perceptual attributes ranging from shrill and strident to constricted and guttural.

Vocal styles

      These types of vocal resonance may be illustrated with a continual series of vocal practices that have been studied through physiologic and electroacoustic analysis. This perceptual series begins with the full, loud, and sonorous sound during the natural vocalizations for laughing, yawning, and yodelling. The rich higher harmonics responsible for the perceptual qualities of these vocalizations are produced by a maximally lowered larynx and greatly widened resonator. At the next step is the sonorous and full sound of so-called covered singing in the German opera style. Rich in higher harmonics (or overtones), this vocal style is performed with lowered larynx, elevated epiglottis, and widened throat cavity. A large group of open or uncovered singing styles lying in the centre of the series extends from the extremely uncovered, flat, and “white” openness of, for example, Spanish flamenco singing, over the flat style of popular singing, to the brightness of Italian bel canto. Approaching the other pole of the series, the large group of functional voice disorders results from constricted resonance of the vocal tract. It is typical of these hyperkinetic (overactive) vocal disorders that the voice is produced with marked laryngeal elevation, constriction of the laryngeal vestibule, and often with pronounced elementary sphincter action of the larynx. The extreme end of this functional series is characterized by the use of the larynx as a primitive sphincter organ as employed in ventriloquism. The maximally elevated and constricted larynx within a very narrow throat cavity produces the high-pitched, thin, muffled, and weak quality of ventriloquism, which is characterized by great reduction of the higher harmonics.

Individual voice quality

      Apart from the variable influences of the vocal tract on the momentary vocal resonance according to training and intention, the supraglottic resonator exerts a constant influence on the vocal quality by shaping its individual characteristics. Just as human faces differ in almost endless variations, the configuration of the supraglottic structures is also highly characteristic, having, in fact, been called the “inner face.” The anatomical shape and the physiologic flexibility of the vocal tract serve to mold the individual vocal personality in at least two ways: by its inborn shape and by the learned behaviour of using it for communication. Any individual's mother tongue shapes his articulatory behaviour into certain patterns, which remain audible in all languages that he learns after puberty and constitute one aspect of the so-called foreign accent. It often is easy to recognize a speaker over the telephone after having listened to his voice a few times without necessarily having met him in person. The ability to recognize a given speaker solely by the quality and inflection of his voice is the basis of efforts to produce “voice prints” that should be as unmistakably identifying as fingerprints are.

Intensity (sound intensity)

      Vocal intensity, the third major vocal attribute, depends primarily on the amplitude of vocal cord vibrations and thus on the pressure of the subglottic airstream. The greater the expiratory effort, the greater the vocal volume. Another component of vocal intensity is the radiating efficiency of the sound generator and its superimposed resonator. The larynx has been compared to the physical shape of a horn. This construction is most efficient in acoustical practice, as seen in the shape of wind instruments, car horns, sirens, loudspeakers, etc. A well-shaped, wide, and flexible vocal tract enhances the projective potential of the voice. Conversely, a morphologically narrow, pathologically constricted, or emotionally tightened throat produces a muffled, constricted sound with poor carrying power.

      The inborn automatic reflexes of laughing and yawning illustrate the resonator action of the vocal organ. Together with a widely opened mouth, flat tongue, elevated palate, and maximally widened pharynx, the larynx assumes a lowered position with maximally elevated epiglottis. This configuration is ideal for the unimpeded radiation of the vocal cord vibrations so that the resulting sound is loud and bright, with a gaily ringing quality; it is the sound of happy laughter. The opposite is present with the painfully tight-throated, choked sobbing of someone crying in despair.

singing and speaking

      A major difference between singing and speaking is psychological in nature. Singing as a physiological performance is exhibited by the majority of human beings who have what seems to be an inborn musical sense that depends on appropriate development of their highest cortical (brain) centres for audition. Although the art of singing in a particular artistic style typically demands formal study, the untrained use of the voice for self-expression through singing develops spontaneously in late childhood and during the period following vocal maturation. Singing involves the use of inherited neural mechanisms that are regulated in part by deeper, subcortical (below the cortex) brain centres, particularly those related to emotional activity. Singing serves many as a way of emotional relief and is related to the social activities of human play. Although song among humans is not as intimately related to sexual propagation as it is in certain animals (e.g., birds), people are still influenced by such sensual stimuli as love songs and madrigals, as well as ceremonial and religious performances.

      The practice of spontaneous singing and of artistic song satisfies emotional needs, but it may not always communicate in a clear ideational sense. When a brain stroke causes aphasia (loss of language for communication), for example, the singing voice often remains normal or at least better preserved, so that some aphasics who cannot say a word can sing with good articulation. This observation has been used to explain that disorders causing aphasia may damage other brain areas than those used for singing. Another example is the severe stutterer who can sing or whisper with fluency. The same dichotomy of communicative speech and declamatory singing is often seen in cases of spastic dysphonia (a peculiar, grave voice disorder without demonstrable brain damage that causes a painfully choked and halting manner of speaking, while singing usually remains undisturbed).

      In the perceptual category, the principal differences between speaking and singing concern the rhythmic (rhythm) patterns. Speaking uses gliding vocal inflections with rapid pitch variations as well as frequent and abrupt intensity modifications for syllabic accentuation. The rhythmical pattern of stresses, unstressed syllables, and breathing pauses is dictated by the meaning of the sentence. The so-called prosodic features of speech (i.e., its melodic inflections) follow the general, regional, and dialectal rules of a given language. In this sense, the essence of speaking is its continual flexibility, variability, and adaptability.

      Singing differs from speaking in the following respects. The melody is followed in precise and discrete steps over customary musical intervals, which commonly are not smaller than semitones in Western music, though quarter and eighth tones are frequently used in Oriental and African music. The vowels are prolonged because they carry the melody. The rhythm of the fixed tonal steps follows the pattern prescribed by the composer and long notes may be sustained for special effects.

      Exceptions to these general rules are found in the portamento, a gliding change between two pitch levels, of Western song, used sparingly as an embellishment. Parlando singing is a speaking type of song, used in the recitativo of Italian opera style. In these intentionally communicative preludes to formal arias—because they tell most of the story—the rhythm of the spoken word is incorporated into the melody, which, in turn, to a certain degree, follows the prosodic vocal inflection.

      The melodic inflection of speech communicates considerable meaning in certain languages, such as in Africa and China. This problem of linguistic tonality (tone), or word melody, requires the appropriate individual selection of various rising, sustained, or falling intervals to express the full meaning of a word. Chinese (Chinese languages) words are monosyllabic, and their multiple meanings cannot be understood without the appropriate prosodic inflection by the “tones” of the particular dialect. If Chinese is spoken without vocal inflection, such as when whispering, intelligibility is reduced by at least one-third.

Synthetic production of speech sounds

      The essence of speech and its artificial re-creation has fascinated scientists for several centuries. Although some of the earlier speaking machines represented simple circus tricks or plain fraud, an Austrian amateur phonetician, in 1791, published a book describing a pneumomechanical device for the production of artificial speech sounds.

      A number of electronic speech synthesizers have been constructed in various phonetic laboratories in the latter half of the 20th century. Some of these are named the “Coder,” “Voder,” and “Vocoder,” which are abbreviations for longer names (e.g., “Voder” standing for Voice Operation Demonstrator). In essence, they are electrical analogues of the human vocal tract. Appropriately arranged electric circuits produce a voicelike tone, a modulator of the harmonic components of this fundamental tone, and a hissing-noise generator to produce the sibilant and other unvoiced consonant sounds. Resonating circuits furnish the energy concentrations within certain frequency areas to simulate the characteristic formants of each speech sound. The resulting speechlike sounds are highly controllable and amazingly natural as long as they are produced as continuants. For example, it is possible to imitate the various subtypes of the hard U.S. sound for R (as in “car”) by moving a few levers or knobs. Difficulties become greater when many other attributes of fluent speech are to be imitated, such as coarticulation of adjacent sounds, fluctuating nasalization, and other segment features and transients of connected articulation. Speech synthesizers have, nevertheless, made a contribution to the study of the various physical characteristics that contribute to the perception and recognition of speech sounds.

      The counterpart of speech synthesizers is the speech recognizer, a device that receives speech signals through a microphone or phono-optical device, analyzes the acoustic components, and transforms the signals into graphic symbols by typing them on paper. Modern models may incorporate computers (computer) to store some of the information that permits the device directly to type from dictation. Early models had great difficulties with the correct spelling of homophonous words (those that sound alike but differ in spelling and meaning) such as “to, too, two” or “threw, through, thru.” Human transcribers usually have no difficulty with these distinctions because they listen to major parts of the sentence to recognize each word from the context and general situation. The computerized machines developed in the 1970s, however, had to be programmed for each detailed aspect of speech recognition that people normally learn through many years of general schooling and specialized training. Moreover, the machines could be effective only for very limited vocabularies and had to be adjusted to each individual speaker.

Godfrey Edward Arnold

Additional Reading

V.E. Negus, The Comparative Anatomy and Physiology of the Larynx (1950), an excellent introduction to the understanding of function and evolution of the voice organ in man and animals; G. Fant, Acoustic Theory of Speech Production (1960), a modern, detailed exposition of acoustic phonetics, the science of the acoustic structure of speech sounds and their production; H. Fletcher, Speech and Hearing in Communication, 2nd ed. (1953), a classic work on the physiology of speech and hearing; P.B. Denes and E.N. Pinson, The Speech Chain (1963), highly recommended for high school and college level students. See also William M. Shearer, Illustrated Speech Anatomy (1979); Roderick P. Singh, Anatomy of Hearing and Speech (1980); Willard R. Zemlin, Speech and Hearing Science: Anatomy and Physiology (1981); and David Ross Dickson and Wilma Maue-Dickson, Anatomical and Physiological Bases of Speech (1982). See also recent issues of these journals: American Speech and Hearing Association (ASHA) Journal (monthly); Journal of Speech and Hearing Disorders (quarterly); and Journal of Speech and Hearing Research (quarterly).

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