Speech (redirected from Speeches)

speech: see language.

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speech

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).

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Speech

A set of audible sounds produced by disturbing the air through the integrated movements of certain groups of anatomical structures. Humans attach symbolic values to these sounds for communication. There are many approaches to the study of speech.

Speech production

The physiology of speech production may be described in terms of respiration, phonation, and articulation. These interacting processes are activated, coordinated, and monitored by acoustical and kinesthetic feedback through the nervous system.

Most of the speech sounds of the major languages of the world are formed during exhalation. Consequently, during speech the period of exhalation is generally much longer than that of inhalation. The aerodynamics of the breath stream influence the rate and mode of the vibration of the vocal folds. This involves interactions between the pressures initiated by thoracic movements and the position and tension of the vocal folds. See Respiration

The phonatory and articulatory mechanisms of speech may be regarded as an acoustical system whose properties are comparable to those of a tube of varying cross-sectional dimensions. At the lower end of the tube, or the vocal tract, is the larynx. It is situated directly above the trachea and is composed of a group of cartilages, tissues, and muscles. The upper end of the vocal tract may terminate at the lips, at the nose, or both. The length of the vocal tract averages 6.5 in. (16 cm) in men and may be increased by either pursing the lips or lowering the larynx.

The larynx is the primary mechanism for phonation, that is, the generation of the glottal tone. The vocal folds consist of connective tissue and muscular fibers which attach anteriorly to the thyroid cartilage and posteriorly to the vocal processes of the arytenoid cartilages. The vibrating edge of the vocal folds measures about 0.92– 1.08 in. (23–27 mm) in men and considerably less in women. The aperture between the vocal folds is known as the glottis. The tension and position of the vocal folds are adjusted by the intrinsic laryngeal muscles, primarily through movement of the two arytenoid cartilages. See Larynx

When the vocal folds are brought together and there is a balanced air pressure to drive them, they vibrate laterally in opposite directions. During phonation, the vocal folds do not transmit the major portion of the energy to the air. They control the energy by regulating the frequency and amount of air passing through the glottis. Their rate and mode of opening and closing are dependent upon the position and tension of the folds and the pressure and velocity of airflow. The tones are produced by the recurrent puffs of air passing through the glottis and striking into the supralaryngeal cavities.

Speech sounds produced during phonation are called voiced. Almost all of the vowel sounds of the major languages and some of the consonants are voiced. In English, voiced consonants may be illustrated by the initial and final sounds in the following words: “bathe,” “dog,” “man,” “jail.” The speech sounds produced when the vocal folds are apart and are not vibrating are called unvoiced; examples are the consonants in the words “hat,” “cap,” “sash,” “faith.” During whispering all the sounds are unvoiced.

The rate of vibration of the vocal folds is the fundamental frequency of the voice (F0). It correlates well with the perception of pitch. The frequency increases when the vocal folds are made taut. Relative differences in the fundamental frequency of the voice are utilized in all languages to signal some aspects of linguistic information.

Many languages of the world are known as tone languages, because they use the fundamental frequency of the voice to distinguish between words. Chinese is a classic example of a tone language. There are four distinct tones in Chinese speech. Said with a falling fundamental frequency of the voice, ma means “to scold.” Said with a rising fundamental frequency, it means “hemp.” With a level fundamental frequency it means “mother,” and with a dipping fundamental frequency it means “horse.” In Chinese, changing a tone has the same kind of effect on the meaning of a word as changing a vowel or consonant in a language such as English.

The activity of the structures above and including the larynx in forming speech sound is known as articulation. It involves some muscles of the pharynx, palate, tongue, and face and of mastication.

The primary types of speech sounds of the major languages may be classified as vowels, nasals, plosives, and fricatives. They may be described in terms of degree and place of constriction along the vocal tract.

The only source of excitation for vowels is at the glottis. During vowel production the vocal tract is relatively open and the air flows over the center of the tongue, causing a minimum of turbulence. The phonetic value of the vowel is determined by the resonances of the vocal tract, which are in turn determined by the shape and position of the tongue and lips.

The nasal cavities can be coupled onto the resonance system of the vocal tract by lowering the velum and permitting airflow through the nose. Vowels produced with the addition of nasal resonances are known as nasalized vowels. Nasalization may be used to distinguish meanings of words made up of otherwise identical sounds, such as bas and banc in French. If the oral passage is completely constricted and air flows only through the nose, the resulting sounds are nasal consonants. The three nasal consonants in “meaning” are formed with the constriction successively at the lips, the hard palate, and the soft palate.

Plosives are characterized by the complete interception of airflow at one or more places along the vocal tract. The places of constriction and the manner of the release are the primary determinants of the phonetic properties of the plosives. The words “par,” “bar,” “tar,” and “car” begin with plosives. When the interception is brief and the constriction is not necessarily complete, the sound is classified as a flap. By tensing the articulatory mechanism in proper relation to the airflow, it is possible to set the mechanism into vibrations which quasiperiodically intercept the airflow. These sounds are called trills.

These are produced by a partial constriction along the vocal tract which results in turbulence. Their properties are determined by the place or places of constriction and the shape of the modifying cavities. The fricatives in English may be illustrated by the initial and final consonants in the words “vase,” “this,” “faith,” “hash.”

The ability to produce meaningful speech is dependent in part upon the association areas of the brain. It is through them that the stimuli which enter the brain are interrelated. These areas are connected to motor areas of the brain which send fibers to the motor nuclei of the cranial nerves and hence to the muscles. Three neural pathways are directly concerned with speech production, the pyramidal tract, the extrapyramidal, and the cerebellar motor paths. It is the combined control of these pathways upon nerves arising in the medulla and ending in the muscles of the tongue, lips, and larynx which permits the production of speech. See Nervous system (vertebrate)

Six of the 12 cranial nerves send motor fibers to the muscles that are involved in the production of speech. These nerves are the trigeminal, facial, glossopharyngeal, vagus, spinal accessory, and the hypoglossal. See Psychoacoustics, Psycholinguistics