Deafness has varying definitions in cultural and medical contexts. In medical contexts, the meaning of deafness is
hearing loss
Hearing loss is a partial or total inability to hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to acquire spo ...
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
Sign languages (also known as signed languages) are languages that use the visual-manual modality to convey meaning, instead of spoken words. Sign languages are expressed through manual articulation in combination with #Non-manual elements, no ...
regardless of
hearing
Hearing, or auditory perception, is the ability to perceive sounds through an organ, such as an ear, by detecting vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is auditory sci ...
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.
Medical context

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:
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conductive hearing loss
Conductive hearing loss (CHL) is a type of hearing impairment that occurs when sound waves are unable to efficiently travel through the outer ear, tympanic membrane (eardrum), or middle ear structures such as the ossicles. This blockage or dysfun ...
,
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sensorineural hearing loss
Sensorineural hearing loss (SNHL) is a type of hearing loss in which the root cause lies in the inner ear, sensory organ (cochlea and associated structures), or the vestibulocochlear nerve (Cranial nerves, cranial nerve VIII). SNHL accounts for a ...
,
* mixed hearing loss, and
*
auditory neuropathy spectrum disorder.
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
This article lists the statutory retirement age in different countries. In some contexts, the retirement age is the age at which a person is expected or required to cease work. It is usually the age at which such a person may be entitled to recei ...
.

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.
Cochlear implants are an option for children and adults with severe or profound hearing loss. Cochlear implants are surgically placed devices that stimulate the cochlear nerve in order to help the person hear. A cochlear implant is used instead of
hearing aids in order to help when someone has difficulties understanding speech. For children, the younger they are at the time of implantation, the better their auditory skill and perception.
Babies with confirmed bilateral profound sensorineural hearing loss may begin the surgical evaluation process for implantation as early as six months, with the US officially allowing the surgery to take place as early as nine months of age.
Children with other medical problems or other types of hearing loss may be considered at a slightly older age.
Parents sometimes have difficulty deciding to get cochlear implants for their child. Many felt a sense of urgency, and, in the end, most parents felt it was beneficial for their child.
Cultural context

In a cultural context,
Deaf culture
Deaf culture is the set of social beliefs, behaviors, art, literary traditions, history, values, and shared institutions of communities that are influenced by deafness and which use sign languages as the main means of communication. When used as ...
refers to a tight-knit
cultural group
An ethnographic group or ethnocultural group is a group that has cultural traits that make it stand out from the larger ethnic group it is a part of. In other words, members of an ethnographic group will also consider themselves to be members of a ...
of people whose
primary language
A first language (L1), native language, native tongue, or mother tongue is the first language a person has been exposed to from birth or within the critical period. In some countries, the term ''native language'' or ''mother tongue'' refers ...
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 who "identifies him/herself as a member of the Deaf community, and other members accept that person as a part of the community",
an example being
children of deaf adults with normal hearing ability.
It includes the set of social beliefs, behaviors, art, literary traditions, history, values, and shared institutions of communities that are influenced by deafness and which use
sign language
Sign languages (also known as signed languages) are languages that use the visual-manual modality to convey meaning, instead of spoken words. Sign languages are expressed through manual articulation in combination with #Non-manual elements, no ...
s as the main means of communication.
While deafness is often included within the umbrella of
disability
Disability is the experience of any condition that makes it more difficult for a person to do certain activities or have equitable access within a given society. Disabilities may be Cognitive disability, cognitive, Developmental disability, d ...
, members of the Deaf community tend to view deafness as a difference in human experience or itself as a language minority.
Many non-disabled people continue to assume that deaf people have no autonomy and fail to provide people with support beyond hearing aids, which is something that must be addressed. Different non-governmental organizations around the world have created programs towards closing the gap between deaf and non-disabled people in developing countries.
As children, deaf people learn literacy differently than hearing children. They learn to speak and write, whereas hearing children naturally learn to speak and eventually learn to write later on.
The Quota International organization, headquartered in the United States, provided immense educational support in the Philippines, where it began offering free education to deaf children in the Leganes Resource Center for the Deaf. The British organisation Sounds Seekers also supported deaf communities by offering audiology maintenance technology in hard-to-reach areas.
The Nippon Foundation supports deaf students at
Gallaudet University
Gallaudet University ( ) is a private federally chartered university in Washington, D.C., for the education of the deaf and hard of hearing. It was founded in 1864 as a grammar school for both deaf and blind children. It was the first school ...
and the
National Technical Institute for the Deaf
The National Technical Institute for the Deaf (NTID) is the first and largest technological college in the world for students who are deaf or hard of hearing. As one of nine colleges within the Rochester Institute of Technology (RIT) in Roches ...
through international scholarship programmes to encourage them to become future leaders in the deaf community. The more aid these organisations give to deaf people, the more opportunities and resources marginalised people have to speak up about their struggles and aspirations. When more people understand how to leverage their privilege for marginalised groups, society can build a more inclusive and tolerant environment for future generations.
History
The first known record of
sign language in history comes from
Plato
Plato ( ; Greek language, Greek: , ; born BC, died 348/347 BC) was an ancient Greek philosopher of the Classical Greece, Classical period who is considered a foundational thinker in Western philosophy and an innovator of the writte ...
's
Cratylus, written in the fifth century BCE. In a dialogue on the "correctness of names",
Socrates
Socrates (; ; – 399 BC) was a Ancient Greek philosophy, Greek philosopher from Classical Athens, Athens who is credited as the founder of Western philosophy and as among the first moral philosophers of the Ethics, ethical tradition ...
says, "Suppose that we had no voice or tongue, and wanted to communicate with one another, should we not, like the deaf and dumb, make signs with the hands and head and the rest of the body?" His belief that deaf people possessed an innate intelligence for language put him at odds with his student
Aristotle
Aristotle (; 384–322 BC) was an Ancient Greek philosophy, Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, a ...
, who said, "Those who are born deaf all become senseless and incapable of reason", and that "it is impossible to reason without the ability to hear".
This pronouncement would reverberate through the ages and it was not until the 17th century when manual alphabets began to emerge, as did various treatises on
deaf education, such as ''Reducción de las letras y arte para enseñar a hablar a los mudos'' ('Reduction of letters and art for teaching mute people to speak'), written by
Juan Pablo Bonet in Madrid in 1620, and ''Didascalocophus, or, The deaf and dumb mans tutor'', written by
George Dalgarno in 1680.
In 1760, French philanthropic educator
Charles-Michel de l'Épée
Charles-Michel de l'Épée (; 24 November 1712 – 23 December 1789) was an 18th-century French philanthropic educator who has become known as the "Father of the Deaf". He founded Institut National de Jeunes Sourds de Paris, the first public sch ...
opened the
world's first free school for the deaf. The school won approval for government funding in 1791 and became known as the "Institution Nationale des Sourds-Muets à Paris". The school inspired the opening of what is today known as the
American School for the Deaf
American(s) may refer to:
* American, something of, from, or related to the United States of America, commonly known as the "United States" or "America"
** Americans, citizens and nationals of the United States of America
** American ancestry, ...
, the oldest permanent school for the deaf in the United States, and indirectly,
Gallaudet University
Gallaudet University ( ) is a private federally chartered university in Washington, D.C., for the education of the deaf and hard of hearing. It was founded in 1864 as a grammar school for both deaf and blind children. It was the first school ...
, the world's first school for the advanced education of the deaf and hard of hearing, and to date, the only higher education institution in which all programs and services are specifically designed to accommodate deaf and hard of hearing students.
Schooling
Parents of deaf and hard-of-hearing children often encounter difficulties when choosing an educational setting for their child. They may consider the needs and abilities of the child, how the school can make accommodations for the child, and the school environment itself.
Both the child and the parent may benefit from trial and error with different schools, to identify the best available environment.
See also
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Auditory neuropathy
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Auditory verbal agnosia
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Auditory-verbal therapy
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Causes of hearing loss
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Cortical deafness
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Cued speech
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Deaf hearing
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Deaf history
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Deaf plus
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Deaf rights movement
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Deaf theatre
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Deafblindness
Deafblindness is the condition of little or no useful hearing and little or no useful sight. Different degrees of vision loss and auditory loss occur within each individual. Because of this inherent diversity, each deafblind individual's needs re ...
*
Deafness by country
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Deaf-community sign language
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Deaf-mute
Deaf-mute is a term which was used historically to identify a person who was either deaf and used sign language or both hearing impairment, deaf and muteness, could not speak. The term continues to be used to refer to deaf people who cannot speak ...
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Diagnosis of hearing loss
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List of films featuring the deaf and hard of hearing
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Models of deafness
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World Hearing Day
References
External links
WHO fact sheet on deafness and hearing loss*
Global audiology,
International Society of Audiology
*
International Ototoxicity Management Group
5 levels of deafness
{{DEFAULTSORT:Deafness
Deafness
Hearing loss
Audiology
Broad-concept articles