Types of Auditory Disabilities
Types of Auditory Disabilities
In some ways, the content of this section is more than you need to know in order to make web content accessible to people who are deaf or hard of hearing, but it is included here in the hope that with increased understanding comes increased appreciation to such individuals, and an increased commitment to providing content that is accessible to them.
The key principle of web accessibility for users with auditory disabilities is:
- Perceivable: because they cannot perceive (hear) auditory content
It should be noted that the use of the word "disabilities" in the title of this section is a controversial choice, considering the attitude of many people in the deaf community. More than any of the other groups of individuals commonly labeled as "disabled," those who are deaf are much less inclined to think of their condition as a disability. We'll read more about this in the last section of this article - Deaf Culture. Still, we have retained the word "disability" in this section, not to provoke controversy, but to underscore the fact that those who are deaf cannot hear audio content, and this is the critical point for web developers to remember.
Deafness is not an all-or-nothing condition. Although there are individuals who are completely deaf, there are also individuals with varying degrees of functional hearing loss. Degrees of hearing loss are often categorized as mild, moderate, severe, profound. Those who refer to themselves as deaf usually have either severe or profound hearing loss. Those with lesser degrees of hearing loss are commonly referred to as hard-of-hearing.
Degrees of Hearing Loss
- Mild hearing loss:
- The inability to hear sounds below about 30 decibels. Speech can be difficult to understand, especially if background noises are present.
- Moderate hearing loss:
- The inability to hear sounds below about 50 decibels. A hearing aid may be required.
- Severe hearing loss:
- The inability to hear sounds below about 80 decibels. Hearing aids are useful in some cases, but are inadequate in others. Some individuals with severe hearing loss communicate principally through sign language; others rely on lip-reading techniques.
- Profound hearing loss:
- The absence of the ability to hear, or the inability to hear sounds below about 95 decibels. Like those with severe hearing loss, some individuals with profound hearing loss communicate principally through sign language; others rely on lip-reading techniques.
Classifications of Hearing Loss
Conductive hearing loss is the result of damage or blockage of the moving parts of the ear. The bones of a healthy inner ear—the malleus (hammer), incus (anvil) and stapes (stirrup)—vibrate in response to sounds. Diseases or injury can lead to the inability of these bones to vibrate properly, preventing the proper detection of auditory information.
Neural hearing loss (nerve deafness) occurs when the hair cells in the cochlea or the auditory nerve is damaged, thus preventing the auditory information from getting to the brain. The bones of the inner ear may vibrate correctly, but the nerves are unable to properly transmit this information for processing by the brain.
High tone hearing loss is, as its name implies, the loss of the ability to hear high tones. One of the most important social consequences is that women's voices are more difficult to understand.
Low tone hearing loss is the inability to hear low tones. Male voices are difficult to hear and understand.
Deaf-blindness is the condition of being both deaf and blind. Individuals who are deaf-blind often communicate by sign language, but they must be able to feel the signs the other person is making, by essentially holding the hands of the other person while conversing. When accessing web content, they generally use refreshable Braille devices that allow them to access all of the textual content of the web page, including alternative text for images.
Causes of Hearing Loss
Most deafness occurs early in life, most often through genetic or perinatal causes. Deafness can also occur as a result of middle ear infections (otitis media), which are most common in young children. It is also possible to experience deafness later in life, through traumatic injury or diseases. Additionally, hearing loss is a common part of the aging process, especially in men.