Speech and Speech Disorders

I INTRODUCTION

Speech and Speech Disorders. Speech is a learned system of communication requiring the coordinated use of voice, articulation, and language skills. Although many animals are physiologically able to use the voice for communicating a wide range of simple messages to others of their species, only humans are able to produce true speech (as opposed to the skills in speech mimicry of such birds as parrots and mynae). In a broad sense, speech is synonymous with language.

II VOICE

Voice, or phonation, is the sound produced in the voice box, or larynx, by the expiration of air through vibrating vocal cords. Voice is defined in terms of pitch, quality, and intensity, or loudness. Optimum pitch, which means the most appropriate pitch for speaking, varies with each individual. Both optimum pitch and range of pitch are fundamentally determined by the length and mass of the vocal cords; within these limits, pitch may be varied by changing the combination of air pressure and tension of the vocal cords. This combination determines the frequency at which the vocal cords vibrate; the greater the frequency of vibration, the higher the pitch.

Another aspect of voice is resonance. After voice is produced, it is resonated in the chest, throat, and cavities of the mouth. The quality of the voice is determined by resonance and the manner in which the vocal cords vibrate; intensity is controlled by resonance and by the strength of the vibrations of the vocal cords.

III ARTICULATION

Articulation refers to the speech sounds that are produced to form the words of language. The articulating mechanism comprises the lips, tongue, teeth, jaw, and palate. Speech is articulated by interrupting or shaping both the vocalized and unvocalized airstream through movement of the tongue, lips, lower jaw, and soft palate. The teeth are used to produce some specific speech sounds.

IV LANGUAGE SKILLS AND OTHER FACTORS

Language is an arbitrary system of abstract symbols agreed upon by any group of people to communicate their thoughts and feelings. Symbols may be verbal or non-verbal, that is, either spoken or written; additionally, non-verbal symbols may be gestures and body movements (See also Sign Language). In spoken language the skills of articulation are used; in written language, spelling is substituted for articulation. Both auditory and visual skills are essential to the comprehension and expression of language.

Rate and rhythm should also be considered in the evaluation of speech. Connected speech should not be so rapid or so slow that it interferes with comprehension. Rhythm is judged mostly in terms of fluency. Good or so-called normal speech cannot be exactly measured or described, however; it can be judged essentially only as it seems to be suitable for the sex, size, age, personality, and needs of the speaker.

V SPEECH DISORDERS

Because speech is a learned function, any interference with learning ability may be expected to cause a speech impairment. The most common interfering conditions are certain neuroses and psychoses, mental retardation, and brain damage, whether congenital or acquired. Articulation itself may be impaired by such physical disabilities as cleft palate, cerebral palsy, or loss of hearing; it may likewise deteriorate as a result of paralysis of any part of the articulating mechanism. Impairment may also be the consequence of unconscious imitation of poor speech models or inadequate perception of auditory stimuli.

Voice disorders, so-called dysphonias, may be the product of disease or accidents that affect the larynx. They may also be caused by such physical anomalies as incomplete development or other congenital defects of the vocal cords. The most frequent cause, however, is chronic abuse of the vocal apparatus, either by overuse or by improper production of the voice; this may result in such pathological changes as growths on or thickening and swelling of the vocal cords.

Disorders of rate and rhythm are generally either psychogenic or have a basis in some neurological disturbance. A notable example of a neurological condition is Parkinson’s disease.

VI SPEECH THERAPY

A speech therapist is a specialist who has been trained to diagnose and treat the various disorders of speech, language, and voice. Because physical, neurological, or psychological conditions often are either responsible for or are related to the speech disorder, the therapist often works as a member of a team, which may include a neurologist, an otolaryngologist (ear and throat specialist), a psychiatrist, a psychologist, a psychiatric social worker, and a speech pathologist.

Speech disorders caused by disease, injury, or malformation fall within the province of the doctor and surgeon. Once these defects are remedied, the speech therapist is responsible for teaching the speech-handicapped person to hear and monitor speech accurately, to think appropriately in verbal terms, and to exercise control over speech disordered by incoordination or emotional influences.

Inasmuch as a hearing loss (see Deafness) will prevent learning by imitation of essential speech patterns and sounds and prevent the individual from monitoring his or her own errors, one of the therapist’s most valuable techniques is the measurement of hearing. Because intellectual capacity and the ability to handle language are closely related, the therapist must also understand how intelligence develops in a young child. The most obvious emotional speech disorder is stuttering, which is often caused by anxiety. The speech therapist uses a programme of speech exercise to reduce this disability. Where necessary, the aid of a psychologist is enlisted; in extreme cases, a psychiatrist assists with psychotherapy.

Loading...

Phonetics

I INTRODUCTION

Phonetics, a branch of linguistics concerned with the production, transmission, and perception of speech sounds. The main field of study is articulatory phonetics but other fields are experimental phonetics and acoustic phonetics. Basic phonetic principles are often applied to other linguistics disciplines, including sociolinguistics (for example, when variations in pronunciation according to social motivations are studied) and historical linguistics (for example, when pronunciation changes are investigated).

II ARTICULATORY PHONETICS

This describes speech sounds genetical, that is, with respect to the ways by which the vocal organs modify the air stream in the mouth, nose, and throat in order to produce a sound. Articulatory phonetics usually takes into account the following factors when describing a sound: air flow, vocal cords, the position of the soft palate, place of articulation, the manner of articulation, the position of the lips. All the vocal activities involved in a sound need not be described, but only a selection of them, such as the place and manner of articulation. Sounds are represented by phonetic symbols and their articulatory definitions. These are abbreviated descriptions of the selected activities taking place during the production of a certain sound. The symbols most commonly used are those adopted by the International Phonetic Association (IPA) and they are written in square brackets “[k]” (phonemic symbols are written between oblique strokes “/k/”). Diacritics can be added to denote, for example, place of articulation.

The organs of articulation are either movable or stationary. Movable organs such as lips, jaws, tongue, soft palate, or vocal cords are called articulators. Stationary parts include the teeth, the alveolar arch and behind them, the hard palate.

A Air Flow

During the production of a sound, the flow of air (in or out of the lungs) determines the type of sound produced. Most speech sounds are made using pulmonic egressive air (air flowing out of the lungs). However, some languages use sounds that do not involve pulmonic (lung) air. These include the click sounds of the Khoisan languages, and glottalic sounds (where the glottis controls the air flow) common in African and Native American languages.

B Vocal Cords

A sound is also affected by the action of the vocal cords, which can vibrate (or not) during sound production. The vocal cords are located in the larynx. A sound is labelled voiced if the vocal cords are vibrating, and unvoiced or voiceless when the absence of vibration (where the cords stay in an open position) is noted. The contrast between a voiced and voiceless sound can be seen in the difference between [b] and [p]. Another action in the vocal cord area is that of a closed glottis (the vocal cords are tightly closed), used in the production of a glottal stop (as in, for example, the “dropped” [t] sound in Cockney English butter).

C Soft Palate

The position of the soft palate (or velum) during the production of a sound determines whether that sound is nasal or oral. When the soft palate is lowered the air is allowed to pass through the nose thus producing a nasal sound (as in English [n]). If the soft palate is raised the air flows out through the mouth, producing an oral sound (as in most English consonants and all English vowels). Air can also flow out through both the nasal and oral cavities when the velum is lowered. This is done during the production of nasal vowels as in the vowel in French bon.

D Place of Articulation

The lips, teeth and hard palate are all places of articulation: the point at which a sound is produced. Sounds made by touching two articulators, for example, the bilabial [p], which requires both lips, or those made by an articulator and a stationary part of the vocal apparatus, are named according to the organs that make the juncture. Reference to the tongue, when it is an articulator, is not expressed; for example, the [t] sound, which is produced when the tongue touches the alveolar ridge, is called alveolar because this is the place of articulation. The hard palate is the place of articulation in the palatal semivowel sound [j], as in the first sound of English yes.

E Manner of Articulation

The manner of articulation is determined by the way in which the speaker affects the air stream with his or her movable organs. This action may consist of stopping the air completely (plosive, for example, [p]); making contact with the tongue but leaving space on either side of it (lateral, for example, [l]); making merely a momentary light contact (flap, as in the Spanish “r” in pero); leaving just enough space to allow a continuing stream of air to produce friction as it passes through (fricative, for example, [f] or [s]); or permitting the air stream to pass over the centre of the tongue without oral friction (vocal: all vowel sounds).

Vowels of different quality are produced by varying the position of the tongue on its vertical axis (high, mid, low) and on its horizontal axis (front, central, back). The speaker may move the tongue gradually upwards and to the front or upwards and to the back, making diphthongal off-glides. For example, a speaker moves the tongue from low to high in pronouncing the first two vowels of Aïda, and from back to front in pronouncing successively the vowel sounds in “who” and “he”. The tongue positions for the vowel sounds [i:] (as in flee), [a] (as in northern UK English cat), [u:] (as in root), and [ ] (as in pot) are the highest and lowest cardinal points on the left and right of the Cardinal Vowel system quadrangle, a framework of vowels at fixed points that can be used as a starting point to determine where an individual speaker’s vowel sounds lie. The vowel sound is known as schwa (as in the first vowel sound in English ago) has the most central position.

When the speaker gives a strong puff of air after the contact, this is called aspiration. If the hand is placed on the lips, aspiration may be observed in the [ph] sound produced at the beginning of the word pie in English (note that a superscript h is used to represent the quality of aspiration when transcribing sounds). In contrast, French [p] sounds characteristically lack aspiration.

F Position of the Lips

The position of the lips is used to describe some sounds, particularly vowels. The quality of a vowel depends on whether the speaker keeps the lips rounded or unrounded and the degree to which the lips are open or closed (using the jaw). The tip of the tongue can also affect vowel quality, as it can be flat or curled up (retroflex, as in some South Asian languages).

III EXPERIMENTAL PHONETICS

Also referred to as Instrumental Phonetics, this is the physical science that collects measurable data about the production of vocal sounds by recording and analysing speech and vocal organs using instruments such as the kymograph, which traces curves of pressure; the spectrograph, which analyses sound waves and represents them visually; the oscilloscope, which has a function similar to a spectrograph but is technologically more advanced; and the X-ray, which allows physiological study. The amount of detail in the measurement of vocal sounds is limited only by the precision of the instrument. Differences are found in every vocal sound.

IV ACOUSTIC PHONETICS

This is the study of the physical properties of speech, that is, speech waves as the output of a resonator (the resonator being the vocal tract coupled with other sources). Sound waves are closer than articulations to the essence of communication, for the same auditory impression can be produced by a normal articulation and by an entirely different sound apparatus, like that of parrots. A spectrograph may be used to record significant characteristics of speech waves and to determine the effect of articulatory activities. Parts of this record of speech waves can be cut out experimentally and the rest played back as sound in order to determine which features suffice to identify the sounds of a language.

V PHONEMICS

This is a study of the sounds of speech in their primary function, which is to make vocal signs that refer to different things sound different. It is the focus of the branch of linguistics called phonology, although phonetic analysis contributes to this study. The phonemes of a particular language are those minimal distinct units of sound that can distinguish meaning in that language. In English, the p sound is a phoneme because it is the smallest unit of sound that can make a difference of meaning if, for example, it replaces the initial sound of “bill”, “till”, or “dill”, making the word “pill”. The vowel sound of “pill” is also a phoneme because its distinctness in sound makes “pill”, which means one thing, sound different from “pal”, which means another. Two different sounds, reflecting distinct articulatory activities, may represent two phonemes in one language but only a single phoneme in another. Thus phonetic [r] and [l] are distinct phonemes in English, whereas these sounds represent a single phoneme in Japanese, just as [ph] and [p] in “pie” and “spy”, respectively, represent a single phoneme in English although these sounds are phonetically distinct.

VI HISTORY

Phonetics is one of the oldest branches of linguistics. The earliest contributions to phonetics were made more than 2,000 years ago by Sanskrit scholars such as the grammarian Panini, who dealt with articulation to keep the pronunciation of ancient rituals unchanged. The first phonetician of the modern world was the Dane J. Matthias, author of De Litteris (1586). The English mathematician John Wallis, who instructed deaf-mutes, was the first (1653) to classify vowels according to their place of articulation. The vowel triangle, the precursor to the quadrangle, was invented in 1781 by the German C. F. Hellwag. The Cardinal Vowel system was laid out by the British phonetician Daniel Jones. Ten years later, the Austrian mechanician Wolfgang von Kempelen invented the machine that produced speech sounds. The German physicist Hermann von Helmholtz, who wrote Sensations of Tone (1863), inaugurated the study of acoustical phonetics; the Frenchman Abbé Jean Pierre Rousselot was a pioneer of experimental phonetics. Late in the 19th century, the theory of the phoneme was advanced by the Pole Jan Baudouin de Courtenay and the Swiss Ferdinand de Saussure. In the United States, the linguist Leonard Bloomfield and the anthropologist and linguist Edward Sapir contributed greatly to phonetic theory. The linguist Roman Jakobson developed a theory of the universal characteristics of all phonemic systems.

See also Language.

Loading...
Loading...