Deafness, most simply defined as an inability to hear. This definition, however, gives no real impression of how deafness affects function in society for the hearing-impaired person. The condition affects all age groups, and its consequences range from minor to severe. Profoundly deaf people have a hearing loss so severe that they cannot benefit from mechanical amplification, whereas hard-of-hearing people often can benefit, to varying degrees, from the use of such amplification.
II TYPES AND CAUSES OF DEAFNESS
Four types of hearing loss may be described. The first, conductive hearing loss, is caused by diseases or obstruction in the outer or middle ear and is not usually severe. Causes of conductive deafness include wax in the ears; infection of the external ear canal; perforated eardrum; glue ear with the loss of free movement of the ossicles (three small bones in the middle ear); otitis media (inflammation of the middle ear); a blockage in the Eustachian tube; and otosclerosis (hereditary form of deafness caused by bone growing into the space separating the middle and inner ear). A person with a conductive hearing loss can generally be helped by a hearing aid. Often conductive hearing losses can also be corrected through surgical or medical treatment. The second kind of deafness, sensorineural hearing loss or nerve deafness, results from damage to the sensory hair cells or the nerves of the inner ear and can range in severity from mild to profound deafness. Such loss occurs at certain sound frequencies more than others, resulting in distorted sound perceptions even when the sound level is amplified. Causes of sensorineural deafness include noise damage (acoustic trauma); ageing; Ménière’s disease; aminoglycoside antibiotics; certain diuretic drugs; aspirin; anti-malarial drugs; and acoustic nerve tumour. The third kind, mixed hearing loss, is caused by problems in both the outer or middle ear and the inner ear. Finally, central hearing loss is the result of damage to or impairment of the nerves of the central nervous system.
Deafness, in general, can be caused by illness or accident, or it may be inherited. Continuous or frequent exposure to sound levels above 85 decibels (dB), such as that produced by loud rock music (where dB can exceed 100 dB), can cause a progressive and eventually severe sensorineural hearing loss. A hearing aid may not help a person with a sensorineural loss.
III EDUCATION AND TRAINING
Until the Middle Ages, most people believed that deaf people were incapable of learning language or of being educated in any way. By the 16th century, however, a few philosophers and educators began to reconsider the condition of deaf people. A Spanish Benedictine monk, Pedro de Ponce, is considered the first teacher of deaf students, and, in 1620, Juan Paulo Bonet, another Spaniard, wrote the first book on educating deaf people. The book contained a manual alphabet similar to the one used today.
During the 18th century, schools were established for deaf children in France by Abbé Charles Michel de l’Épée and, in Germany, by the educator Samuel Heinicke. The conflict that exists to this day as to whether deaf children should be educated by oral (lip-reading and speech) or manual (signs and finger spelling) methods dates from this time. The Abbé de l’Épée was a manualist and Heinicke an oralist; each knew of and studied the other’s methods.
Unless provided early with special training, people profoundly deaf from birth are incapable of learning to speak. Deafness from birth causes severe sensory deprivation, which can seriously affect a person’s intellectual capacity or ability to learn. A child who sustains a hearing loss early in life may lack the language stimulation experienced by children who can hear. The critical period for neurological plasticity is up to age seven. Failure of acoustic sensory input during this period results in failure of formation of synaptic connections and, possibly, an irremediable situation for the child. A delay in learning language may cause a deaf child’s academic progress to be slower than that of hearing children. The academic lag tends to be cumulative, so that a deaf adolescent may be four or more academic years behind his or her hearing peers. Deaf children who receive early language stimulation through sign language, however, generally achieve academically alongside their hearing peers.
IV COMMUNICATION SYSTEMS
Increasingly, the philosophy of total communication is being followed in schools and classes for deaf children. This philosophy encourages the combined use of whatever communication methods are appropriate to the deaf child, including speech, lip-reading, signing, Cued Speech, finger spelling, art, electronic media, mime, gesture, and reading and writing. Finger spelling is a system in which hand shapes and positions correspond to the letters of the written alphabet so that fingerspelling can be called “writing in the air”. Sign language (SL) is a language based on gestures, lip and eyebrow movements, and grammatical rules. Most countries have their own sign language, each as different as the languages spoken by the hearing is, and many with different dialects. Probably the most widely used are American Sign Language (ASL), which has no grammatical similarities with the English language whatsoever and takes a lot of its vocabulary from Old French Sign Language. British Sign Language (BSL) is used in the United Kingdom, Indian Sign Language in India, New Zealand Sign Language (NZSL) in New Zealand, and so on (see Sign Language).
The signs in SL are word-like units with both concrete and abstract meanings. Signs are made by either one or both hands, which assume distinctive shapes and movements. Spatial relations, directions, and orientation of the hand movements, as well as facial expressions and body movement, make up the grammar of SL. A number of invented (that is, not native languages) manual communication systems use the sign vocabulary of SL in combination with other hand movements to approximate the syntax and grammar of Standard English (see Paget-Gorman Sign System). Cued Speech is a system in which eight hand movements indicate the pronunciation of every syllable being spoken. It is a speech-based method that supplements lip-reading. Oral communication is the term used by educators to denote the teaching of speech as an expressive skill to deaf children. It means that speech and lip-reading are the only means of communication used for the transmission of thoughts and ideas.
V WORK PROSPECTS
Increasing numbers of deaf students are pursuing post-secondary educational programmes at tertiary education establishments that have special provisions and programmes for deaf students.
Today deaf people are employed in almost every vocation, except those where the good hearing is an obvious requirement—for example, being a commercial pilot. Deaf people are doctors, lawyers, teachers, and members of the clergy, as well as secretaries, accountants, chemists, farmers, and labourers. Discrimination does exist, as it does for other minority groups, but employers are increasingly hiring deaf people and making adjustments for them, such as adding special telephone devices or providing secretary-interpreters or other aids that enable the deaf employee to function effectively in work.
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.
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.
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.
Communication, the process of transmitting and receiving ideas, information, and messages. The rapid transmission of information over long distances and ready access to information have become conspicuous and important features of human society, especially in the past 150 years, and in the past two decades, increasingly so.
Communication between two people is an outgrowth of methods developed over centuries of expression. Gestures, the development of language, and the necessity to engage in joint action all played a part.
A Communication Among Animals
Charles Darwin pointed up the importance of communication and expressiveness in biological survival. Recent studies have dealt with the range of animal communication. For example, when bees discover a source of nectar, they reveal its location to the other bees on returning to the hive. They communicate the distance to the source by means of a dance; the direction is indicated by the angle of the axis of the dance, and the amount of nectar by the vigorousness of the dance. Scientists have recorded and identified birdcalls for courting, mating, hunger, food bearing, territoriality, warning, and distress. Research into the behaviour of whales and dolphins has revealed that they have relatively elaborate vocal signals and that they communicate over long distances underwater. See Animal Behaviour.
The origin of language is subject to considerable speculation. Some words may be imitative of natural sounds. Others may have come from expressions of emotion, such as laughter or crying. Language, some theorists believe, is an outgrowth of group activities, such as working together or dancing. Another theory holds that language developed from basic sounds that accompanied gestures.
Although it is difficult to quantify the world’s languages, it is estimated that almost 7,000 are spoken in the world today, most of them grouped in families. As some languages grow, others decline and disappear. The changes in language reflect class, gender, profession, age group, and other social forces, such as the effects of technology on everyday life.
C Symbols and Alphabets
Early peoples sought the means by which to record language. They drew and painted on cave walls to convey messages and they used signs and symbols to designate tribe or ownership. As human knowledge expanded, writing became necessary in order to transmit information. The earliest writing was pictographic, with symbols representing objects. The first pictographic writing was cuneiform, by which wedge-shaped characters were inscribed with a stylus on a clay tablet. Cuneiform later developed ideographic elements; the symbol came to represent not only the object but also ideas and qualities associated with it.
Writing, however, continued to convey only the meaning, not the sound, of words. Eventually, cuneiform incorporated phonetic elements, that is, signs that represented certain sounds. Egyptian hieroglyphs underwent a similar development. This system progressed from pictograms to ideograms; it incorporated signs for consonants, but it never developed into an alphabet. The alphabet, invented in the Middle East, was carried by the Phoenicians to Greece, where vowel sounds were added to it. The Cyrillic alphabet was adapted from the Greek; the Latin alphabet developed in countries farther to the west where the Roman culture was dominant.
III COMMUNICATING AT A DISTANCE
With the growth of civilization and the development of written languages came the need to communicate regularly at longer distances as well, so as to conduct the trade and other affairs of nations and empires.
A Paper and Printing
The Egyptians discovered that a kind of writing material could be made from strips of the stem of the papyrus plant. A later discovery was parchment, which was made by preparing both sides of a sheet of animal tissue for writing uses. Meanwhile, in China, about 105 ads, the method of papermaking was discovered. It took over 1,000 years for the technique to travel to Europe, and it came at a time when a great demand for books began to appear. In the middle of the 15th century, the German printer Johann Gutenberg used movable type for the first time in Europe to print the Bible. This technique expanded the opportunities for learning and led to radical changes in the way people lived. It contributed to the growth of individualism, the Reformation, rationalism, scientific inquiry, and regional literature that reflected the rise of nationalism. Newssheets called corantos began to appear in Europe in the 17th century. At first devoted to trade and other business news, they eventually developed into the first true newspapers and magazines providing the dissemination of current information to the public at large.
Printing techniques and applications developed rapidly in general over the next centuries, especially following the growth of steam power and its use for driving presses in the early 19th century and, somewhat later, the invention of typesetting machines. The first such device, called the Linotype, was patented in 1884 by the German-American Ottmar Mergenthaler; a wide range of increasingly rapid and large-scale printing techniques appeared in succeeding decades. By the late 20th century both typesetting and the printing process itself relied largely on computer technology (see also Desktop Publishing).
B Postal Services
Among the many kinds of communication services in ancient times, the most notable were the relay system of the Persian empire. People on horseback could transfer written messages at one relay station to fresh carriers who could then transport it to another station. From this system, the Romans developed their own system of posts (Latin, positus, the origin of the term “postal service”). Similar systems were also employed in the Far East.
Although the postal services of medieval Europe were largely privately owned, the rise of nationalism that followed the Renaissance also resulted in the growth of government-owned postal systems. Private operations had largely come to an end by the 17th and 18th centuries.
C Speedier Long-Distance Communication
Since their inception, modern postal systems have continued to develop along with the growth of railways, motor vehicles, aircraft, and other carriers; recent years have also seen the introduction of electronic mail services. Over the centuries, however, people have also sought means for communicating more rapidly over long distances than conventional modes of transport would allow. Early methods included drumbeats, fire, smoke signals, and instruments such as a ram’s horn. In time, bugle calls and drums came to play an important role in communicating military commands. During the Middle Ages, homing pigeons were used to transmit messages. In the early 1790s, Claude Chappe, a French scientist, and engineer, began the construction of a system of semaphore stations, a visual telegraph capable of sending a message many kilometres in a few minutes. Some of these tall towers, similar to later rail semaphore towers, were as far as 32 km (20 mi) apart. The system was copied in Britain and the United States. Such semaphore systems, which variously used telescopes and sun-reflecting mirrors, remained slow because each signal had to be repeated at each station to verify the accuracy of transmission.
With the beginnings of a modern understanding of the phenomenon of electricity in the 18th century, inventors started to search for ways in which electrical signals might be employed for the rapid relay of messages over long distances. The first practical telegraph system, however, was not produced until the 19th century, when two such inventions were announced in the same year of 1837: one, in Britain, by Charles Wheatstone and William F. Cooke, and the other, in America, by Samuel F. B. Morse. Morse also developed the code system of dots and dashes—Morse code—that was universally adopted for the new medium. Morse code was in worldwide use until February 1, 1999, when it was replaced by the Global Maritime Distress and Safety System, which uses satellite and terrestrial radio communication. Various refinements of telegraphy appeared in later decades. For example, in 1874 Thomas Edison developed quadruplex telegraphy, by which two messages could be transmitted simultaneously in two directions. Modern offshoots of telegraphy are seen in teletype, telex, and facsimile transmission.
Although telegraphy marked a great advance in rapid long-distance communication, early telegraph systems could convey messages only letter by letter. The search was therefore also on for some means of voice communication by electricity as well. Early devices that appeared in the 1850s and 1860s were capable of transmitting sound vibrations but not true human speech. The first person to patent the electric telephone in the modern sense was the American inventor Alexander Graham Bell, in 1876. At the same time, Edison was also in the process of finding a way to record and then reproduce sound waves, paving the way for the invention of the record player. By the late 20th century, such developments as transoceanic cable, fibre optics, and satellite technology had revolutionized the use of the telephone. Mobile telephones (see Cellular Radio) are increasingly in use.
Early telegraph and telephone systems depended on the physical medium of wires for message transmission, but scientific developments indicated other possibilities. The theory of the electromagnetic nature of light was advanced by the British physicist James Clerk Maxwell in 1873 in his Treatise on Electricity and Magnetism. The theories of Maxwell were validated by the German physicist Heinrich Rudolf Hertz. In 1887 Hertz discovered electromagnetic waves, thus laying the technical foundation for wireless telegraphy.
During the following decade, much experimentation was conducted with the sending of wireless signals. In 1896, the Italian inventor Marchese Guglielmo Marconi transmitted a wireless signal from Penarth to Weston-super-Mare in England, and in 1901 sent a wireless signal across the Atlantic Ocean, from Cornwall. The vacuum tube with two elements was invented by the British physicist John Ambrose Fleming in 1904. A valuable improvement was made a few years later by the American inventor Lee De Forest, who invented a three-element vacuum tube that provided the basis for many electronic devices. The first radio broadcast was made in 1906, in the United States. The first broadcast of opera, from the Metropolitan Opera House in New York, was transmitted by De Forest in 1910. By 1920 several radio stations began transmitting in the United States, and by 1923 the British Broadcasting Corporation (BBC) was transmitting in the United Kingdom; by 1925 there were 600 radio stations worldwide. Nowadays almost every home in Britain and other countries has a radio.
G Picture Communication
Early manuscripts were illuminated with intricately drawn pictures. In the late 15th century woodcuts for illustrations came into use in printed books. At the end of the 18th-century lithography was invented, permitting the mass reproduction of artwork. In 1826, using sensitized metal plates exposed for eight hours, the French physicist Joseph Nicéphore Niépce produced the world’s first photograph. Building on Niépce’s work, the French painter and inventor Louis Jacques Mandé Daguerre discovered a chemical developing process that permitted a greatly reduced exposure time, producing the photograph known as the daguerreotype.
As the 19th century progressed, various methods were devised to give photographs and photography the illusion of motion. In 1891 Edison patented the kinetoscope, a machine for projecting moving pictures that he had first demonstrated in 1889. In 1895 the French chemist and industrialist Louis Jean Lumière and his brother Auguste Marie Lumière, also a chemist, demonstrated and patented the cinematography, which successfully projected moving pictures. In the late 1920s sound was added to films.
The system of transmitting moving images has many roots. One is the invention of a scanning disc by the German television pioneer Paul Gottlieb Nipkow in 1884. Another landmark in the development of television was the invention in 1923 by the Russian-American electronics engineer Vladimir Kosma Zworykin of the iconoscope for transmitting and the kinescope for receiving images over a distance. In 1926 John Logie Baird used this system to demonstrate the first electrical transmission of moving images. This stimulated further developments in the United States, Britain, and Germany. In Britain, the BBC began television broadcasts in 1927, using Baird’s system, and by 1937 had begun the world’s first high-quality public broadcasting service.
At the end of World War II, television captured the popular imagination in the United States. By the end of the 20th century, watching television was Britain’s most popular leisure activity, with 94 percent of households having a colour television; 98 percent of all American households have at least one television receiver. The advent of cable, satellite, and digital television have increased dramatically the number of channels and services available.
Television has expanded worldwide; the communications satellite makes possible the transmitting of programmes between continents and events can be shown simultaneously as they happen in most parts of the world. Closed-circuit television is used by banks to identify cheques, by airlines to present flight information, by doctors to study techniques used in operations, and in numerous other ways. The development of video recording has also revolutionized the capacity to store, retrieve, and transmit information.
One of the most dramatic advances in communication potential—data communications—is found in the field of computer technology. Since the first development of the modern electronic digital computers in the 1940s, computerization has infiltrated almost every area of society in nations with advanced technology. Computers are available in many formats for use in industries, businesses, hospitals, schools, transport networks, and individual homes—and computer networks and auxiliary devices provide a means for people with the use of a personal computer for the rapid transmission of a wide range of data. Use of the Internet has revolutionized access to information for the business world, libraries, education, and individuals. Publishing is increasingly happening in electronic form (see Electronic Publishing).
J Laser Technology
The laser is also of great potential importance for the future of communications. Modulated beams of the coherent light produced by lasers can transmit a much larger number of messages at a time than can ordinary telephone systems. Prototype laser communications networks are already in operation, and they may eventually replace to a large degree the use of radio waves in telephony. Laser beams are also ideal for use in space for satellite communications systems.
K Communications and Education
Films on various subjects and other forms of audio-visual education can be a vital element in classroom instruction and audio-visual devices are used in many schools in developed industrial nations. These include pictures, posters, charts, models, mock-ups, slides, filmstrips, and videos. Tape recorders are used extensively in the teaching of languages.
Educational broadcasting has widened enormously access to education through such establishments as the Open University in Britain and School of the Air in Australia. Schools are increasingly linking into the Internet and incorporating the use of satellite data and CD-ROM technology. Rapid advances in computer technology are likely to have a dramatic impact on education (see Information Technology in Education and National Grid for Learning).
L Communications and Cultural Change
Historically, the means of communicating have grown alongside the increased power of people to shape their physical world as well as with their increasing interdependence. With the telecommunications and data communications revolutions has been the evolution of the world as a “global village”. The influence of the new communications media has increased the study of their effects. It is believed by some that the individual media tend to reinforce personal views rather than to convert people to other views, and by others that political conversion and influence, depending on who controls which medium of transmitting information, is prevalent. None the less, the changing communications media have proven to have long-term effects, which bring subtle but very important changes to views and perceptions of the audience.