THE NATURE OF DEAFNESS

DEFINITION OF DEAFNESS

Deafness is one of the largest categories of impairment in South Africa and encompasses the full spectrum of hearing loss – from mild loss of hearing to total deafness – yet as an invisible impairment it is often misunderstood and the severity of its impact upon both the child and his family is underestimated. It is believed that a better understanding of the concept ‘deafness’ will enable non-specialist educators to develop more effective classroom practices.

Although deafness is a multifaceted concept which, due to the complex nature of the condition, cannot be easily defined, Myklebust (1997:12) defined the term deaf as referring to those individuals in whom the sense of hearing is non-functional for the ordinary purposes of life. Deafness can also be described as the physical impairment that results in those affected by it being unable to hear, and usually brings to mind the need for hearing aids, speech therapy and the use of signing and gestures as a means of communication.

THE NATURE OF DEAFNESS

In order to understand the concept ‘deafness’, the concept ‘hearing’ must be understood. Hearing, which is sometimes referred to as audition, involves the gathering and interpreting of sounds.

Each part of the ear serves a purpose in translating sound waves from the environment into meaningful information to the brain. The outer ear is called pinna. It is the first point of contact between the individual and the sound. The outer ear gathers the sound and sends it down the auditory canal, or external auditory meatus. At this point, the sound enters the middle ear and sets the eardrum, or tympanic membrane, into motion (Schirmer 2001:2). What started as acoustical energy in the outer ear is turned into mechanical energy in the middle ear.

Between the eardrum and the oval window, which is the window to the inner ear, are the three smallest bones in the human body. These bones, the ossicles, are individually named the hammer (malleus), the anvil (incus), and the stirrup (stapes). When the eardrum vibrates, the ossicles are set into motion, and the sound is carried through the oval window into the inner ear. The inner ear contains the cochlea and the semicircular canals. The cochlea is considered the main sensory organ for hearing. The fluid in the ducts of the snail-shaped cochlea moves in response to the mechanical energy released by the ossicles. Tiny hair cells within the cochlea convert the mechanical energy into electrical impulses that are transmitted by neurons along the auditory nerve to the brain (Schirmer 2001:3).

The Eustachian tube, which runs between the middle ear and the back of the throat, controls air pressure in the middle ear (Schirmer 2001:3). The semicircular canals in the inner ear control the sense of balance.

Types of hearing loss

Frederickson and Cline (2002:364) explain that hearing loss is usually categorised in terms of the main site of the damage, as this is what normally determines the nature of the impairment:
• Conductive: The physical transmission of sound in the outer or middle ear is interrupted.
• Sensory-neural: Damage has occurred to neural transmission in the inner ear or auditory nerve. This is less common and more serious. It is also called perceptive or nerve deafness.
• Mixed: This involves both conductive and sensory-neural loss.
• Central: Damage has occurred to the auditory nerve in the brain stem or the hearing centres of the cortex. This is also known as cortical deafness.

Frederickson and Cline (2002:362) further explain that in order to understand hearing loss it is necessary to appreciate the key feature of sound level. Sound level is the volume of a sound. It is measured in decibels (dB). Zero decibels (0dB) indicate the point at which the average person with normal hearing can detect the faintest sound. Each succeeding number of decibels that a person cannot detect indicates a certain degree of hearing loss. Deafness can be distinguished as mild (26-40dB), moderate (41-55dB), moderate-severe (56-70dB), severe (71-90dB), and profound (91db and above) (Andrews, Leigh & Weiner 2004:15-20).

Age of onset and aetiology of hearing loss

Owing to the close relationship between hearing loss and language, professionals are particularly interested in determining the age at which hearing loss was first detected. The earlier the hearing loss occurs in a child’s life, the more difficult it will be for that child to develop the language of the hearing society (e.g. English). For this reason, professionals frequently use the terms pre-lingual deafness (those who are born deaf) and post-lingual deafness (those who become deaf at some time after birth (Hallahan & Kauffman 2006:322).

Frederickson and Cline (2002:366) indicate the following causes of pre-lingual deafness:
• Maternal illness, for instance German measles/rubella contracted by the mother, especially during the first trimester of her pregnancy. This can cause deafness as the virus attacks the foetus. A second maternal illness known to cause deafness is cytomegalovirus (CMV).
• Genetic deafness means that there is deafness in the family and it is thus hereditary in nature.
• Birth complications and/or premature birth (defined as birth before 37 weeks) is also known to cause hearing loss in some infants.

Post-lingual deafness is caused primarily by ear infections (otitis media) and meningitis. Other less prevalent causes are accidents and blows to the head, high fevers, mumps and measles, and also the side effects caused by certain types of medication.
• Meningitis is an infection (viral or bacterial) of the central nervous system, specifically the covering of the brain, which could extend into the brain and ears, thus causing deafness. Learners who become deaf as a result of contracting meningitis are usually profoundly deaf and the majority of these learners do not benefit from hearing aids.
• The most common form of hearing loss in childhood, otitis media, fluctuates over time.

If a learner catches a cold with symptoms such as a running nose, coughs and sneezes, the infection can spread into the middle ear via the Eustachian tube, which leads there from the back of the throat. While the middle ear is affected, the mechanisms that enable it to conduct sound are blocked, so that the learner’s hearing is impaired. In most cases, as soon as the infection has been effectively treated, hearing is recovered. Since some learners have repeated infections, they can experience bewildering fluctuations in their ability to make sense of what is being said around them. Parents and educators can find their behaviour puzzling, and their language development and educational progress may eventually be affected (Frederickson & Cline 2002:366).

Identification and assessment of deaf learners

Frederickson and Cline (2002:366) further emphasise that it is essential that educators be alert to signs of unidentified hearing loss in learners in their classes. It is worth raising a query about possible hearing loss if it is observed that a learner:
• is often slow to react to instructions or repeatedly asks what to do even though they have just been told;
• watches others to see what they are doing and then follows;
• constantly asks others to repeat what they have said;
• hears sometimes, but not always, for example when a learner hears when standing on one side of the room, but not when standing on the opposite side;
• often misinterprets information and questions, or responds to only part of what has been said;
• is unable to locate a speaker or the source of a sound, especially in noisy conditions;
• has a tendency to daydream or shows poor concentration, especially during group discussions or when a story is being read aloud;
• sometimes makes inappropriate comments, as though not having followed the topic of conversation;
• shows delayed language development (e.g. immature use of syntax, limited vocabulary);
• finds it difficult to repeat words or sounds or to remember the names of people and places;
• sometimes shouts without apparently realising that he or she is being noisy;
• makes speech errors (e.g. omits the consonants from the end of words, misses out s, f, th, t, ed, en);
• confuses words that sound similar (e.g. hat, fat, vat);
• fixes his or her eyes on the speaker as though lip-reading;
• sometimes becomes disruptive during lessons that require learners to listen;
• experiences difficulties with reading, spelling and/or writing; and
• seems to have frequent colds and coughs.

Given the impact that hearing loss can have on the development of early language, it is important to identify deaf learners as early as possible (Downs & Yoshinaga-Itano 1999:80). Anderson (1999:16) underlines the fact that early testing is vital in supporting a deaf learner to adapt to the hearing world. Every learner who may suffer from hearing loss needs thorough testing of his or her hearing and middle-ear function. A child is never too young to have a hearing test (Anderson 1999:17). Magnuson (2000:7) adds that young children with profound hearing loss who receive early intervention services have much better outcomes than those who do not.

Many learners with hearing loss need some type of technology to provide them with better access to auditory information. Even a learner with mild hearing loss may need some assistance in very noisy situations (Mahshie et al. 2006:33). The following section provides information about the sensory devices most commonly used by learners with hearing loss in order to gain access to sound.