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Hearing impairment

(see also Deaf)

Hearing impairment is a defect in the perception of sound by the brain. The two major categories of hearing loss are:

  • sensorineural, or neurological, impairment and
  • loss due to malfunction of the physical apparatus of the ear.

The treatment and prognosis of hearing impairment is somewhat different for each category, as well as the specific type of impairment. In many cases, the cause of the impairment is unknown. In other cases, the cause may be genetic ("runs in the family"), environmental (due to noise), or brought on by disease (such as rubella or meningitis).

Table of contents

Sensorineural hearing impairments

Sensorineural hearing loss occurs when the nerves that communicate information from the cochlea to the brain malfunction such that the information transmitted does not reach the auditory centers of the brain. There are several different types.

The most common type is a broad category in which the threshold at which sound is perceived is significantly louder than the human norm (approximately 30 decibels). In this case, it is surmiseable that the nerves leading from the inner ear require extra energy to become activated prior to signalling the auditory centers. Persons with this type of loss can often be successfully treated with the use of hearing aids[?].

Another type of loss is one in which sound is perceived, but the auditory centers of the brain are unable to make sense of the data received. This is different from the damage that occurs in aphasias, where the language centers of the brain are impaired. For the most part, speech therapy in persons with this type of loss is unsuccessful, and they are dependent upon sign language for communication.

Other, rarer, types of loss include losses in specific pitch ranges, and certain brain dysfunctions in which the person cannot separate multiple auditory stimuli.

Impairments due to abnormalities of the ear

Hearing loss can also occur due to abnormalties in various parts of the ear. The success of treatment depends in part on which portion of the ear is affected. Those who suffer from a condition in which the three bones behind the eardrum are fused, rendering them immobile, may be treated for a time with hearing aids. If the fusion is complete, surgery may be an option, as may be the use of cochlear implants. The latter are particularly effective for those who lose their hearing after acquiring spoken language.

In cases where the eardrum and/or outer structures of the ear are affected, loss may be minimal. Treatment may not be needed, or is facilitated through the use of hearing aids designed to accommodate the abnormality.

When the inner ear or cochlea is affected, it may be difficult to distinguish from a sensorineural loss. This is particularly true if tympanometric readings (measurements of the vibration of the ear drum) are normal. Here, the course of and success of treatment depend partly on the underlying cause. Where the cause is abnormal growths, such as polyps or cysts, these may be surgically removed. If the cause is infection, then medication and drainage of the canal are indicated. Other causes require other methods of treatment.

Effects of hearing impairment

When hearing loss is congenital (present at birth) or occurs pre-lingually, spoken language acquisition can be severely affected. The severity of impact is directly proportional to the level of loss. Those born with minor impairments may simply "sound funny". Those with severe impairments are likeliest to be noted first, particularly by their parents or caretakers, since these children do not begin speaking at a normal age.

Other symptoms of congenital hearing impairment include lack of reaction to loud noises; delayed language acquisition; disordered speech; and appearing to ignore adults when spoken to. Children who are suspected of having a hearing loss should be screened by a trained audiologist. This is because general practitioners and pediatricians are often not adequately trained in testing for and diagnosing hearing impairment and deafness. In the United States, up until the 1970s, the severely impaired and deaf were sometimes not diagnosed until the age of four. This is unfortunate, as the prognosis for the acquisition of intelligible speech increases the earlier a child's impairment is detected, and where indicated, fitted for hearing aids. Those who cannot learn spoken language even with assistance benefit from learning sign language as early as possible.

Post-lingual impairments are far more common. In the most typical case, hearing loss is gradual, and often detected by the affected person's family and friends long before the person themself will acknowledge the disability. In cases where the cause is environmental, the treatment is to eliminate the environmental cause and fit the person with hearing aids. When the loss is due to heredity, total deafness is often the end result. On the one hand, persons suffering from gradual deterioration of their hearing are fortunate in that they have learned to speak. On the other, they often suffer from social isolation, because they can no longer understand their friends, who cannot communicate effectively with them. Ultimately, unless the affected person becomes skilled in speech-reading ("lip-reading"), she will depend on sign language for communication.

In some cases, the loss is extremely sudden. Most often, the cause is unknown. Sometimes, it can be traced to specific diseases, such as meningitis, or to ototoxic medications, such as Gentamicin. In both cases, the final degree of loss varies. Some suffer only partial loss, while others become profoundly deaf. In the former case, hearing aids can be used with varying degrees of success, depending on the exact nature of the loss. In the latter, ultimately the affected person will depend on speech-reading and/or sign language for communication.

Partial Loss of Hearing

Hearing impaired persons with partial loss of hearing may find that the quality of their hearing varies from day to day, or from one situation to another. They will also, to a greater or lesser extent depend on both hearing-aids and lip-reading, similarly to more severely disabled people. They may perhaps not always be aware of it, but they do admit to it being important to see the speaker's face in conversation.

Some people may merely find it difficult to differentiate between words that begin with consonantal sounds such as the fricatives s, z, or th, or the plosives d, t, b, or p. They may be unable to hear thin, high-pitched or metallic noises, such as birds chirping or singing, clocks ticking, etc.

Others will find their condition so much worse if circumstances in their immediate environment affect the way they are able to use their hearing-aids, or prevent them from employing their lip-reading skills. A room with a high ceiling, sound-absorbing materials or acoustic tiles on the walls will affect the sound of a speaker's voice adversely. The position of the listener,too, sitting at a right angle to the speaker at a long seminar table, thus being able to hear only with one, maybe the ineffectual ear, can make a difference. Difficulties can also arise for the listener trying to lip-read, if the speaker is sitting with his back against the light-source and is in this way obscuring his face.

The speaker's accent; the topic under discussion, possibly with many unfamiliar words; the softness of his voice; possibly his having a speech impediment; a habit of holding a hand in front of his mouth or turning his face away at times: all these tendencies cause problems to the hard-of-hearing, especially when they have to rely on lip-reading. The rustling of papers, and notebook pages being turned are precisely the noises that will be the first thing hearing-aids pick up.

Social Impact of hearing loss

In children, hearing loss can lead to social isolation for several reasons. First, the child experiences delayed social development that is in large part tied to delayed language acquisition. It is also directly tied to their inability to pick up auditory social cues. A child who uses sign language and is deaf, or identifies with the deaf sub-culture does not generally experience this isolation, particularly if he attends a school for the deaf, but may conversely experience isolation from his parents if they do not know sign language. A child who is exclusively or predominantly oral (using speech for communication) will experience social isolation from her hearing peers, particularly if no one takes the time to explicitly teach her social skills that other children acquire independently by virtue of having normal hearing. Finally, a child who has a severe impairment and uses some sign language may be rejected by her deaf peers, because of her understandable hesitation in abandoning the use of her verbal and speech-reading skills. The deaf community views this hesitation as a rejection of their own culture and its mores, and therefore will reject her out of self-defense.

Those who lose their hearing later in life, such as in late adolescence or adulthood, face their own challenges. For example, they must adjust to living with the adaptive devices that make it possible for them to live independently. They must also adapt to using hearing aids and/or learning sign language. Loneliness and depression can arise as a result of isolation (from the inability to communicate with friends and loved ones) and difficulty in accepting their disability. The challenge is made greater by the need for those around them to adapt to the person's hearing loss.

How to communicate with someone who has a hearing loss

  1. Ask the person what will be most useful for them; this varies from one individual to another.
  2. Speak normally. Do not shout or over-enunciate. Both of these make it more difficult to understand speech, not less.
  3. Conversely, do not mumble, cover your mouth, or whisper when speaking. All of these can conceal vital speech-reading cues that hearing impaired people use to decipher what is being said. A "favorite" pet peeve of the hearing impaired is people who speak from another room - How are they to speech-read with a wall between them and the speaker?
  4. If asked to repeat yourself, don't. Rephrase instead. By using different words, your friend will be able to use two data sets to understand what you meant. (This is good advice for those with normal hearing, too!) Obviously, if only one word was missed, you can try just repeating that word, or a synonym. This is the area where people vary most: some hearing-impaired people find rephrasing very frustrating, because they have to start over: when a sentence is repeated, they can put together the syllables or words they heard the first time with those in the repetition. When in doubt, ask "Should I repeat that exactly?"
  5. Reduce background noise by turning off the TV and radio, and closing windows. All of these can provide distractions that cause communication to break down completely. They also impede the perception of whatever auditory cues your friend is able to pick up and use.
  6. For small children learning to talk, use context to help them decipher what you are saying. (Additionally, some studies indicate that hearing impaired children who are allowed to lead conversation acquire speech much more successfully than those whose parents attempt to guide conversation for them.)

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