Definitions+and+Characteristics+of+Hearing+Impairments

Characteristics, Forms, Causes, and Prevalence of Hearing Loss

Any person living in Canada, regardless of age, gender, ethnic background, geographic location, occupation, educational background or socio-economic status, can experience hearing loss. The social, emotional, educational and rehabilitative needs of these individuals can differ significantly, resulting in the need for diverse services, technological aids and programs. This page will begin this discussion by explaining the characteristics, forms, causes, and prevalence of hearing loss.

To understand how and why hearing loss happens, it helps to know how the hearing works. For hearing to occur, there are two different pathways by which sound waves produce the sensation of hearing. The first way is through air conduction; this is when “sound waves move through the air in the external auditory canal (the "ear canal" between the outside air and your eardrum). The sound waves hit the tympanic membrane (eardrum) and cause the tympanic membrane to move” (Smith and Carbin, 2010). The vibrations on the tympanic membrane then travel to the ** cochlea ****,** which is filled with liquid and lined with cells that have thousands of tiny hairs on their surfaces. The sound vibrations make the tiny hairs move. The outer hair cells take the sound information, amplify it and tune it. The inner hair cells send the sound information to your hearing nerve, which then sends it to your brain, allowing you to hear.
 * How Hearing Works **

The second pathway hearing occurs is through bone conduction. Hearing by bone conduction occurs when a sound wave or other source of vibration causes the bones of the skull to vibrate. These vibrations are transmitted to the fluid surrounding the cochlea and hearing results.

Hearing can be affected at different times in a person's development and by different factors. “A congenital ("at or before birth") hearing loss can occur from either genetic or environmental causes (Ex. viral infections, drugs or alcohol ingested by the mother during pregnancy; injury during birth; oxygen deficiency, etc.). Causes of adventitious ("after birth") hearing loss can include exposure to noise in the environment, tumours, infections as well as the aging process” (Richardson, 2006). Hearing loss can also be described as either prelingual which occurs before a person acquired a spoken language or postlingual, occurring after a person has acquired a spoken language.
 * Forms and Causes of Hearing Loss **

Hearing loss is can be categorized into two broad types; conductive or sensorineural hearing loss. Other forms of hearing loss include mixed hearing loss, unilateral hearing loss, bilateral hearing loss and progressive hearing loss. Conductive hearing loss results from physical problems with the movement of the sound wave through the ear. Many conditions of conductive hearing loss result from fluid build-up in the middle ear as a result of colds, allergies, a perforated eardrum, impacted earwax, ear infections, or the presence of foreign matter in the ear. Richardson (2006) states that sensorineural hearing loss results from damage to the hair cells or nerves that receive sound waves. This can happen when there is over exposure to loud noise which causes the hair cells on the cochlea to become less sensitive, as well as from pressure build up commonly found in divers. Sensorineural hearing loss can also happen if head trauma occurs which results in the fracture of the temporal bone which will disrupt the nerves of the auditory system.

Hearing loss is classified as mixed when both conductive and sensorineural hearing loss are present. If only one ear is affected with a hearing loss, it is referred to as a unilateral hearing loss. When both ears are affected, it is known as bilateral hearing loss. A progressive hearing loss is where over time, the hearing becomes progressively worse in one or both ears.

Hearing is measured in decibels, which are used to indicate a sounds magnitude. A normal conversation is measured at 60 decibels of sound; a rock concert produces 110 decibels. If you can hear sounds between 0 and 25 decibels most of the time, your hearing is normal or near normal. If you only hear sounds above 25 decibels, your hearing loss may be mild, moderate, severe, or profound. Mild hearing loss which is a loss of up to 40 decibels, these individuals have trouble in hearing ordinary conversation. “A minimal hearing loss may not be a problem for an adult, but it can seriously affect the overall development of a person who is in the process of learning language, developing communication skills, and acquiring knowledge” (Irwin, 2008). Moderate hearing loss is between the loss of 40 and 60 decibels, where voices must be raised to be heard. Severe hearing loss is the loss of 60 decibels; these individuals must be shouted at to be heard. Profound hearing loss is the loss of 90 decibels or more.
 * Measuring Hearing Loss **

Hearing loss can have many different effects on the individual, based on the degree of their hearing loss. The Educators’ Resource Guide (2009) outlines these effects.
 * Effects of Hearing Loss **

Students with **minimal or mild hearing loss** may: Students with **moderate hearing loss** may Students with **severe hearing loss** may Students with **profound hearing loss** may Hearing impairment is a disability affecting about 1 in 10 North Americans. Berke (2009) states that about 3 in 1,000 babies are born with hearing impairment, making it the most common birth defect. Severe impairment at birth is about 1 in 1,000, development of hearing impairment before adulthood is about 1 in 250 children with normal hearing at birth. Hearing loss in one ear, whether it is mild, moderate or severe affects 1 in 20 children. Teaching and recognizing students that experience hearing loss in your class may be difficult to spot if they do not want to share with you their difficulty of hearing. Some common signs that students are experiencing hearing loss may include loss of attention, poor communication with other students in their class, the lack of socializing or they use many gestures to communicate.
 * miss some consonants
 * experience mild difficulty with auditory language learning
 * experience difficulty listening at a distance or in noisy situations
 * miss quiet speech sounds
 * experience speech/language delays
 * appear to be inattentive
 * hear almost no speech sounds at normal levels
 * make speech sound errors
 * experience learning difficulties related to language delays
 * need to be less than two meters away from speaker for best listening distance
 * hear no speech sounds at normal levels
 * speak, but their speech may be difficult to understand
 * experience learning difficulties related to language delays
 * appear to be inattentive to verbal communication (may not realize that speaker is speaking)
 * hear no speech or other sounds
 * experience extreme difficulty understanding speech
 * produce little or no verbal language
 * learn by visual cues or American Sign Language

According to the World Health Organization, the term "deaf" should only be applied to individuals with hearing impairment so severe that they cannot benefit from sound amplification or hearing aid assistance. Hearing can be amplified in a couple of ways; research shows that a cochlear implant is known to be the most beneficial. Other forms to help treat hearing loss are through hearing aids and FM Systems.

With the technology that is now available to those with hearing loss, almost anyone is able to hear again. A cochlear implant is a small, complex electronic device that can help to provide a sense of sound to a person who is profoundly deaf or severely hard-of-hearing. The implant consists of an external portion that sits behind the ear and a second portion that is surgically placed under the skin. This device has however begun a dispute of the deaf community. Individuals that choose not to receive treatment such as a cochlear implant view themselves as a different community as those who do have cochlear implants. The individuals with no hearing treatments believe their communication is just another language, just as if someone was to go to a country with a different speaking language (Ex. French person trying to understand Russian) that French person would not be able to communicate with the Russian. It is the same as a person who does not understand sign language and trying to communicate with them. As Davidson (2009) states, many people in the deaf community consider cochlear implant technology an assault on them and their way of life. For them, not hearing is normal and part of who they are; by pushing technology to 'fix' this, mainstream society is in essence providing technology to change who they are or get rid of them. The services required to meet the needs and concerns of deaf, hard-of-hearing, and those elderly individuals who have been deaf for all or most of their lives differ significantly. Debate over the best approach to the education of deaf children will continue to be of concern as research continues to grow on language acquisition and learning. The impact of environmental factors (such as noise, disease and head injury) on hearing loss also must be addressed. Societal attitudes toward people with hearing loss and the personal impact that hearing loss has on the individual are also areas of concern. As teachers we will have to address all of these issues if and when we encounter an individual with a hearing impairment in our class.

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