Deafness

Overview
The word deaf is used differently in different contexts, and there is some controversy over its meaning and implications. In scientific and medical terms, deafness generally refers to a physical condition characterized by lack of sensitivity to sound. Notated as deaf with a lowercase d, this refers to the audiological experience of someone who is partially or wholly lacking hearing. In legal terms, deafness is defined by degree of hearing loss. These degrees include profound or total deafness (90 dB - 120 dB or more of hearing loss), severe (60 dB - 90 dB), moderate (30 dB - 60 dB), and mild deafness (10 dB - 30 dB of hearing loss). Both severe and moderate deafness can be referred to as partial deafness or as hard of hearing, while mild deafness is usually called hard of hearing.

Within the Deaf community, the term "Deaf" is often capitalized when written, and it refers to a tight-knit cultural group of people whose primary language is signed, and who practice social and cultural norms which are distinct from those of the surrounding hearing community. This community does not automatically include all those who are clinically or legally deaf, nor does it exclude every hearing person. According to Baker and Padden, it includes any person or persons who "identifies him/herself as a member of the Deaf community, and other members accept that person as a part of the community."

Most deaf people, at least in developed countries, have some knowledge of the dominant language of their country. This may include the ability to lip read, to speak, or to read and write. Having some knowledge of both the dominant language and sign language is called bimodal bilingualism.

Demographics
The global deaf population is roughly estimated to be 0.1% of the total population (1 in 1000). The figure is likely to be higher in developing countries than developed countries due to restricted access to health care, and, in some cultures, due to the high rate of intrafamilial marriages. The great majority of people with less than average hearing are elderly or developed hearing loss after leaving school. According to the U.S. National Center for Health statistics, approximately three quarters of deaf and hard-of-hearing Americans experienced the onset of hearing loss after age 18.

Causes of deafness

 * Genetic disorders:
 * Osteogenesis imperfecta
 * Leopard syndrome (multiple lentigines syndrome)
 * Otosclerosis
 * Robinson type ectodermal dysplasia
 * Cockayne syndrome
 * Bjorn pili torti and deafness syndrome
 * Multiple synostosis syndrome
 * Hunter syndrome
 * Taybi oto-palato-digital syndrome
 * Hereditary nephritis
 * Mohr syndrome
 * Hurler syndrome
 * Waardenburg syndrome
 * Kartagener syndrome
 * Fronto-metaphyseal dysplasia syndrome
 * Morquio syndrome
 * Trisomy 13 S
 * Treacher Collins syndrome
 * Stickler syndrome
 * Congenital:
 * Rubella syndrome
 * Congenital atresia of the external auditory canal
 * Congenital cytomegalovirus
 * Congenital perilymphatic fistula
 * Fetal methyl mercury effects
 * Fetal iodine deficiency effects
 * Infectious:
 * Meningitis
 * Mumps
 * Measles
 * Ear infection (otitis media)
 * Scarlet fever
 * Traumatic:
 * Traumatic perforation of the eardrum
 * Skull fracture (temporal bone)
 * Acoustic trauma such as from explosions, fireworks, gunfire, rock concerts, and earphones
 * Barotrauma (differences in pressure)
 * Toxic:
 * Aminoglycoside antibiotics
 * Ethacrynic acid - oral
 * Aspirin
 * Chloroquine
 * Quinidine
 * Age-related:
 * Age-related hearing loss (presbycusis)
 * Occupational:
 * Any occupation with exposure to loud noises on a continuous day-to-day basis can result in hearing loss due to nerve end damage. Increased attention to conditions in the work environment has markedly decreased the likelihood of work-related hearing loss. See Noise-induced hearing loss.
 * Other:
 * Meniere's disease
 * Acoustic neuroma
 * Temporary hearing loss can be caused by:
 * The build-up of wax in the ear canal
 * Foreign body lodged in the ear canal
 * Injury to the head
 * Allergy
 * Blocked Eustachian tubes
 * Scarred or perforated eardrum
 * Ear infections (chronic otitis externa, chronic otitis media, malignant otitis externa)
 * Reaction to medication such as aminoglycosides, chloroquine, quinidine

Categories of deafness and hearing impairment
These categories may be overlapping. Deafness or hearing impairment may be: Age of onset is also a significant factor.
 * Unilateral – loss of hearing in one ear only
 * Pre-lingual – deafness at birth or deafness acquired before language is learned
 * Peri-lingual – deafness acquired while in the midst of learning a first language
 * Post-lingual – acquired after a language has been learned
 * Partial – limited hearing loss
 * Progressive – hearing loss which increases over time
 * Profound – complete or near-complete inability to hear
 * Tone deaf – inability to distinguish between relative pitch (in music)
 * Tinnitus – hearing damage characterized by a high pitched ringing in the ears which drowns out other sounds

Deaf identity and culture
Within deaf culture, it is asserted that the label is one of identity, not audiological status. It is seen by them as akin to an ethnic division. It describes shared experiences in the world, not only those directly related to sight and sound (the increased awareness of one over the other) but also the cultural experiences that often inevitably follow from that. The term deaf then, used by many of those who are within the category, has little to do with an ability or inability to hear. Because of all this, and many other sociological forces, you will find some who identify themselves as deaf with much more ability to hear than many who self-identify as hearing or hard of hearing. In print, you can sometimes ascertain that the word is being used to reference the cultural identification because many people now capitalize the word when using it as a cultural label.

People who are part of Deaf culture typically use a sign language (such as American Sign Language) as their primary language and often emphatically see themselves as not disabled, but rather as members of a cultural or language minority. Members of this group use Deaf as a label of cultural identity much more than as an expression of hearing status. Hearing or hard of hearing people may also be considered culturally Deaf if they participate in Deaf culture and share Deaf cultural values; this is sometimes referred as 'attitudinal deafness'.

Children of deaf adults
Children of deaf adults (CODAs) with normal hearing ability may consider themselves, and be considered, culturally Deaf or as members of the deaf community. In some cases they may need speech therapy due to limited exposure to spoken language. An organization, also called CODA, was established in 1983 and now holds annual conferences. There are also support groups for Deaf parents who may be concerned about raising their hearing children, as well as support groups for adult CODAs.

There are also several camps established for CODAs, such as the one at Camp Mark Seven which hosts two separate 2-week programs for CODAs, one from age 9 to 12 and one for CODAs from age 13 to 16 and it usually occurs during the summer, from the last week of June to mid-August.

Notable children of deaf adults

 * Alexander Graham Bell; both his mother and his wife, Mabel Hubbard, were deaf.
 * Edward Miner Gallaudet, founder of Gallaudet University, the world's only university for deaf and hard of hearing students. He is the son of Sophia Fowler Gallaudet and Thomas Hopkins Gallaudet, founder of the American School for the Deaf, the first school for the deaf in the U.S.
 * Homer Thornberry, a United States Representative from the 10th congressional district of Texas from 1948 to 1963.
 * Keith Wann, with two other Deaf actors, perform regularly in a troupe called Iceworm, to showcase the cultural and linguistic barrier faced between the deaf and hearing worlds in a comedic fashion.
 * Lon Chaney, Sr., American actor raised by deaf parents, whose upbringing allowed him to better communicate in silent film.
 * Lou Fant, actor, acting coach in Hollywood, California.
 * Lou Ann Walker, who wrote A Loss for Words, a story about her experience as one of three siblings growing up with two deaf parents.
 * Louise Fletcher, American, Academy Award, Best Actress for One Flew Over the Cuckoo's Nest. In 1975, when Fletcher won the Academy Award for Best Actress, she spoke and signed her acceptance speech for the benefit of her deaf parents.
 * Richard Griffiths, English actor.
 * Stefan LeFors, Canadian football quarterback for the Edmonton Eskimos.

Deaf vs. hard of hearing vs. hearing-impaired
Deaf generally implies a profound loss of hearing; someone with a partial loss of hearing is more likely to be referred to as hard of hearing or the qualified partially legally deaf. People with varying degrees of hearing loss have also been referred to as hearing-impaired

The term hard of hearing may be used to describe all degrees of hearing loss up to and including total deafness. In the case of profound deafness this may be political correctness, a euphemism for the simpler and accurate "deaf." Interestingly, this is seen as a euphemism only from the side of the mainstream. The Deaf community does not generally aspire to be hearing and sees the hard of hearing label as an indication of a mindset that views them pathologically.

Total deafness is quite rare. Most deaf people can hear a little. However, since hearing loss is generally frequency-based rather than amplitude-based, a deaf person's hearing may not be usable, if the normal frequencies of speech lie in the impaired range.

People with a moderate hearing loss, of about 36–50 dB, generally describe themselves as "partially deaf." Others who were born hearing, but who have partially lost their hearing through illness or injury are "deafened." Those with a slight hearing loss (eg. about 16–35 dB hearing loss), or have lost some of their hearing in old age may prefer an informal term such as "hard of hearing" or "hearing-impaired".

Those with some functional hearing generally do not take part in the Deaf community, and typically work and socialize with hearing people to the best of their ability. People with all degrees of hearing impairment may encounter discrimination when looking for work, while at their jobs, or when socializing with hearing people.

Other meanings of 'deaf'
Deaf is also used as a colloquialism to refer to a recalcitrant individual or someone unwilling to listen, obey or acknowledge an authority or partner. The third line of Shakespeare's Sonnet 29 provides an example:

When in disgrace with fortune and men's eyes I all alone beweep my outcast state, And trouble deaf heaven with my bootless cries,