Deafness

Deafness has varying definitions in cultural and medical contexts. In medical contexts, the meaning of deafness is hearing loss that precludes a person from understanding spoken language, an audiological condition. In this context it is written with a lower case d. It later came to be used in a cultural context to refer to those who primarily communicate with a deafness aid or through sign language regardless of hearing ability, often capitalized as Deaf and referred to as "big D Deaf" in speech and sign. The two definitions overlap but are not identical, as hearing loss includes cases that are not severe enough to impact spoken language comprehension, while cultural Deafness includes hearing people who use sign language, such as children of deaf adults.

In a medical context, deafness is defined as a degree of hearing difficulties such that a person is unable to understand speech, even in the presence of amplification. In profound deafness, even the loudest sounds produced by an audiometer (an instrument used to measure hearing by producing pure tone sounds through a range of frequencies) may not be perceived by the person. In total deafness, no sounds at all, regardless of amplification or method of production, can be heard.

Neurologically, language is processed in the same areas of the brain whether one is deaf or hearing. The left hemisphere of the brain processes linguistic patterns whether by signed languages or by spoken languages.

Deafness can be broken down into four different types of hearing loss:

All of these forms of hearing loss impair a person's hearing so they are not able to perceive or interpret sounds correctly. These different types of hearing loss occur in different parts of the ear, which make it difficult for the information being heard to get sent to the brain properly.

For each of these types, there are four different levels or amounts of hearing loss. The first level is mild hearing loss. This is when someone is still able to hear noises, but it is more difficult to hear the softer sounds. The second level is moderate hearing loss, and this is when someone can hear almost nothing when someone is talking to them at a normal volume. The next level is severe hearing loss. Severe hearing loss is when someone can not hear any sounds when they are being produced at a normal level, and they can only hear minimal sounds that are being produced at a loud level. The final level is profound hearing loss, which is when someone is not able to hear any sounds except for very loud ones.

Millions of people globally live with deafness or hearing impairments. The 2005 Survey of Income and Program Participation (SIPP) indicated that fewer than 1 in 20 Americans are deaf or hard of hearing at a level that makes normal conversations difficult to hear; more than half of these people are over retirement age.

Several solutions are available for many people with hearing impairments. Hearing aids are a common device. Additionally, people may use devices that use blinking lights instead of noises for alarm clocks or other notifications.