Glossary of deafness terms

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A

Example of subtitles (Charade, 1963)

Canadian Deaf Theatre

Group of deaf people, 2010 (01)

Deaf School Boys

• Abductor spasmodic dysphonia - sudden, involuntary muscle movements that force vocal folds (formerly known as vocal cords) open, keeping them from vibrating and making it difficult to produce sound. (see also adductor spasmodic dysphonia and mixed spasmodic dysphonia.)

• Acoustic neurinoma - tumor, usually benign, which may develop on the hearing and balance nerves and can cause gradual hearing loss, tinnitus, and/or dizziness. Sometimes called vestibular schwannoma. (see also neurofibromatosis type 2.)

• Acoustic spectograph - research instrument that measures voice frequency and clarity.

• Acquired apraxia of speech - loss or impairment of speech caused by damage to the parts of the brain that control the ability to speak.

• Acquired deafness - loss of hearing that occurs or develops some time during the lifespan but is not present at birth.

• Acute otitis media - ear infection, usually caused by bacteria; when the middle ear becomes infected and swollen, trapping fluid and mucus behind the eardrum.

• Adductor spasmodic dysphonia - sudden, involuntary muscle movements that cause vocal folds (formerly known as vocal cords) to slam together and stiffen, making it difficult for them to vibrate and produce sound. (see also abductor spasmodic dysphonia and mixed spasmodic dysphonia.)

• Adenoid - small pad of infection-fighting tissue located near the eustachian tube.

• Ageusia - loss of the sense of taste.

• Albinism - lack of normal pigment in the skin, eyes, and hair.

• Alport syndrome - hereditary condition characterized by kidney disease, sensorineural hearing loss, and sometimes eye defects.

• American Sign Language (ASL) - manual language with its own syntax and grammar, used primarily by people who are deaf.

• Analog aids - hearing aids that convert sound waves into electric signals and then amplify the sound.

• Anosmia - absence of the sense of smell.

• Aphasia - total or partial loss of the ability to use or understand language; usually caused by stroke, brain disease, or injury.

• Aphonia - complete loss of voice.

• Apraxia - inability to execute a voluntary movement despite being able to demonstrate normal muscle function.

• Articulation disorder - inability to correctly produce speech sounds (phonemes) because of imprecise placement, timing, pressure, speed, or flow of movement of the lips, tongue, or throat.

• Assistive devices - technical tools and devices such as alphabet boards, text telephones, or text-to-speech conversion software used to aid individuals who have communication disorders perform actions, tasks, and activities.

• Attention deficit hyperactivity disorder (adhd) - disorder that begins in childhood, but can continue through adolescence and adulthood. Symptoms include difficulty staying focused and paying attention, difficulty controlling behavior, and hyperactivity (over-activity).

• Audiologist - health care professional who is trained to evaluate hearing loss and related disorders, including balance (vestibular) disorders and tinnitus, and to rehabilitate individuals with hearing loss and related disorders. An audiologist uses a variety of tests and procedures to assess hearing and balance function and to fit and dispense hearing aids and other assistive devices for hearing.

• Auditory brainstem response test - a test for brain functioning in comatose, unresponsive, etc., patients, and for hearing in infants and young children; involves attaching electrodes to the head to record electrical activity from the hearing nerve and other parts of the brain.

• Auditory nerve - eighth cranial nerve that connects the inner ear to the brainstem and is responsible for hearing and balance.

• Auditory neuropathy - hearing disorder in which sound enters the inner ear normally, but is impaired when signals move from the inner ear to the brain.

• Auditory perception - ability to identify, interpret, and attach meaning to sound.

• (central) auditory processing disorder - disorder in which the brain and ears do not communicate effectively, making it difficult for someone to interpret the sounds that make up speech.

• Auditory prosthesis - device that substitutes or enhances the ability to hear.

• Augmentative devices - tools that help individuals with limited or absent speech to communicate, such as communication boards, pictographs (symbols that look like the things they represent), or ideographs (symbols representing ideas).

• Aural rehabilitation - techniques used with people who are hearing impaired to improve their ability to speak and communicate.

• Autism - brain disorder that begins in early childhood and persists throughout adulthood; affects three crucial areas of development: communication, social interaction, and creative or imaginative play.

• Autoimmune deafness - individual's immune system produces abnormal antibodies that react against the body's healthy tissues.

• Autosomal - describes genetic material (chromosomes or genes) that are not gender-related.

B

• Balance - biological system that enables individuals to know where their bodies are in the environment and to maintain a desired position. Normal balance depends on information from the labyrinth in the inner ear, from other senses such as sight and touch, and from muscle movement.

• Balance disorder - disruption in the labyrinth, the inner ear organ that controls the balance system, which allows individuals to know where their bodies are in the environment. The labyrinth works with other systems in the body, such as the visual and skeletal systems, to maintain posture.

• Barotrauma - injury to the middle ear caused by a reduction of air pressure.

• Benign paroxysmal positional vertigo - balance disorder that results in sudden onset of dizziness, spinning, or vertigo when moving the head.

• Bilateral hearing loss - hearing loss in both ears.

• Brainstem implant - auditory prosthesis that bypasses the cochlea and auditory nerve. This type of implant helps individuals who cannot benefit from a cochlear implant because the auditory nerves are not working.

• Bone-anchored hearing aid - hearing aid attached to the bone behind the ear that transmits sound vibrations directly through the skull to the inner ear, bypassing the middle ear entirely; often used by people with middle-ear problems or deafness in one ear.

• Bony labyrinth - stiff outer wall of the inner ear composed of three fluid-filled structures: the vestibule, the semicircular canals, and the cochlea.

• Broca's aphasia - disorder caused by damage to a brain region that controls speech (called broca’s area), which makes it difficult for someone to produce written or spoken language.

C

• Canal aid - hearing aid that fits nearly invisibly into the ear canal and is available in two styles: completely-in-the-canal  (cic) and in-the-canal (itc); not recommended for young children or for people with severe to profound hearing loss because the reduced size of canal aids limits their power and volume.

• Captioning - text display of spoken words, presented on a television or a movie screen, that allows a deaf or hard-of-hearing viewer to follow the dialogue and the action of a program simultaneously.

• Carrier - a person who has only one copy of a recessive disorder gene with a change in it. The person "Carries" the changed gene but shows no symptoms of the disorder. If both parents are carriers, each child has a 1 in 4 chance of inheriting two changed genes and showing the disorder.

• Central auditory processing disorder - inability to differentiate, recognize, or understand sounds; hearing and intelligence are normal.

• Chemosensory - perception of chemical signals by the senses; for example, taste and smell are the result of chemosensory perception.

• Chemosensory disorders - diseases or problems associated with the sense of smell or the sense of taste.

• Cholesteatoma - accumulation of dead cells in the middle ear, caused by repeated middle ear infections.

• Chronic otitis media with effusion - repeated occurrences of otitis media with effusion (ear infection), in which fluid remains in the middle ear after the infection is gone.

• Cochlea - snail-shaped structure in the inner ear that contains the organ of hearing.

• Cochlear implant - medical device that bypasses damaged structures in the inner ear and directly stimulates the auditory nerve, allowing some deaf individuals to learn to hear and interpret sounds and speech.

• Cognition - thinking skills that include perception, memory, awareness, reasoning, judgment, intellect, and imagination.

• Chronic otitis media with effusion - repeated occurrences of otitis media with effusion (ear infection), in which fluid remains in the middle ear after the infection is gone.

• Completely-in-the-canal (cic) hearing aid - hearing aid that is custom-molded to fit deeply into the ear canal; useful for mild to moderate hearing loss in adults. (see also in-the-canal (itc) hearing aid.)

• Computed tomography (ct or cat) - a procedure for taking x-ray images from many different angles and then assembling them into a cross-section of the body. This technique is generally used to visualize bone.

• Conductive hearing impairment - hearing loss caused by dysfunction of the outer or middle ear.

• Contact ulcer - open sore in mucous membranes such as those that line the vocal folds (formerly known as vocal cords); often the result of voice overuse such as frequent singing, yelling, or coughing.

• Cued speech - method of communication that combines speech reading with a system of handshapes placed near the mouth to help deaf or hard-of-hearing individuals differentiate words that look similar on the lips (e.G., bunch vs. Punch) or are hidden (e.G., gag).

• Cytomegalovirus (congenital) - one group of herpes viruses that infects humans and can cause a variety of clinical symptoms, including deafness or hearing impairment; infection with the virus may be either before or after birth.

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D

• Decibel - unit that measures the intensity or loudness of sound.

• Developmental apraxia of speech - neurologically based speech disorder that interferes with a child's ability to correctly pronounce sounds, syllables, and words.

• Developmental stuttering - disorder in which speech is disrupted by involuntary repetition and prolongation of sounds, syllables, words, or phrases; occurs in young children still learning speech and language skills.

• Digital aids - hearing aids that convert sound waves into numerical codes—similar to a computer’s binary code—and then amplify the sound.

• Dizziness - physical unsteadiness, imbalance, and lightheadedness associated with balance disorders.

• Dysarthria - group of speech disorders caused by disturbances in the strength or coordination of the muscles of the speech mechanism as a result of damage to the brain or nerves.

• Dysequilibrium - any disturbance of balance.

• Dysfluency - disruption in the smooth flow or expression of speech.

• Dysgeusia - distortion or absence of the sense of taste.

• Dyslexia - learning disability characterized by reading difficulties. Some individuals may also have difficulty writing, spelling, or working with numbers.

• Dysosmia - distortion or absence of the sense of smell.

• Dysphagia - difficulty swallowing.

• Dysphonia - any impairment of the voice or speaking ability.

• Dyspraxia of speech - in individuals with normal muscle tone and speech muscle coordination, partial loss of the ability to consistently pronounce words.

• Dystonia - abnormal muscle tone of one or more muscles.

E

• Ear infection - presence and growth of bacteria or viruses in the ear.

• Ear wax - yellow secretion from glands in the outer ear (cerumen) that keeps the skin of the ear dry and protected from infection.

• Electrocochleography - technique that records electrical activity of the inner ear in response to sounds; used to help confirm the diagnosis of ménière’s disease.

• Endocrinologist - a physician who specializes in diagnosing and treating disorders of the body's glands and hormones.

• Endolymph - fluid in the labyrinth (the organ of balance located in the inner ear that consists of three semicircular canals and the vestibule).

• Endolymphatic duct - short, fluid-filled canal that connects the inner ear to a balloon-shaped structure near the brain called the endolymphatic sac.

• Endoscope - illuminated tube-shaped instrument used to look directly into a body cavity such as the throat.

• Enlarged vestibular aqueducts (eva) - vestibular aqueducts are narrow, bony canals that travel from the inner ear to inside the skull. A vestibular aqueduct is often considered enlarged if it is greater than 1.0 millimeter in size. Research suggests that most children with eva will develop some degree of hearing loss.

• Eustachian tube - a small passageway on either side of the head that connects the upper part of the throat to the middle ear. It supplies fresh air, drains fluid, and keeps air pressure between the nose and the ear at a steady level.

F

• Fm amplifier - wearable device that amplifies sounds from a distant environment; is particularly effective when a sound’s source is relatively far away, such as in a crowd or in a classroom.

G

• Genetic counselor - a health professional who provides information and support to individuals and families who have a genetic disease or who are at risk for such a disease.

• Geneticist - a scientist or physician who specializes in genetics (how children inherit traits from their parents).

• Global aphasia - loss of speech caused by a serious injury to the region of the brain that controls speech and language.

• Gustation - act or sensation of tasting.

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H

• Hair cells - sensory cells of the hearing and balance systems in the inner ear; they are topped with hair-like structures called stereocilia.

• Haptic sense - sense of physical contact or touch.

• Haptometer - instrument for measuring sensitivity to touch.

• Hearing - series of events in which sound waves in the air are converted to electrical signals, which are sent as nerve impulses to the brain, where they are interpreted.

• Hearing aid - electronic device that brings amplified sound to the ear. A hearing aid usually consists of a microphone, amplifier, and receiver.

• Hearing carry-over (hco, also called voice carry over) - type of call provided by a phone service that allows a speech-impaired person who can hear to communicate with another party using an operator who speaks the caller’s typed messages.

• Hearing disorder - disruption in the normal hearing process that may occur in outer, middle, or inner ear, whereby sound waves are not converted to electrical signals and nerve impulses are not transmitted to the brain to be interpreted.

• Hereditary hearing impairment - hearing loss passed down through generations of a family.

• Hoarseness - abnormally rough or harsh-sounding voice caused by vocal abuse and other disorders such as gastroesophageal reflux, thyroid problems, or trauma to the larynx (voice box).

• Hypogeusia - diminished sensitivity to taste.

• Hyposmia - diminished sensitivity to smell.

I

• Inner ear - part of the ear that contains both the organ of hearing (the cochlea) and the organ of balance (the labyrinth).

• In-the-canal (itc) hearing aid - hearing aid that is custom-molded to fit a person’s ear canal, but doesn’t fit as deeply as a completely-in-the-canal (cic) aid; useful for mild to moderate hearing loss in adults. (see also completely -in-the-canal (cic) hearing aid.)

K

• Kallmann's syndrome - disorder that can include several characteristics such as absence of the sense of smell and decreased functional activity of the gonads (organs that produce sex cells), affecting growth and sexual development.

L

• Labyrinth - organ of balance located in the inner ear. The labyrinth consists of three semicircular canals and the vestibule.

• Labyrinthine hydrops - excessive fluid in the organ of balance (labyrinth); can cause pressure or fullness in the ears, hearing loss, dizziness, and loss of balance.

• Labyrinthitis - viral or bacterial infection or inflammation of the inner ear that can cause dizziness, loss of balance, and temporary hearing loss.

• Landau-kleffner syndrome - childhood disorder of unknown origin which often extends into adulthood and can be identified by gradual or sudden loss of the ability to understand and use spoken language.

• Language - system for communicating ideas and feelings using sounds, gestures, signs, or marks.

• Language disorders - any of a number of problems with verbal communication and the ability to use or understand a symbol system for communication.

• Laryngeal neoplasms - abnormal growths in the larynx (voice box) that can be cancerous or noncancerous.

• Laryngeal nodules - noncancerous, callous-like growths on the inner parts of the vocal folds (vocal cords); usually caused by vocal abuse or misuse.

• Laryngeal papillomatosis - rare condition caused by human papilloma virus infection in which non-cancerous tumors grow inside the larynx (voice box), on the vocal folds (formerly known as vocal cords), or in air passages that connect the nose and lungs; treatable with surgery and medication.

• Laryngeal paralysis - loss of function or feeling of one or both of the vocal folds caused by injury or disease to the nerves of the larynx.

• Laryngectomy - surgery to remove part or all of the larynx (voice box).

• Laryngitis - hoarse voice or the complete loss of the voice because of irritation to the vocal folds (vocal cords).

• Laryngoscopy - procedure used to see, directly or indirectly, the vocal folds (formerly known as vocal cords) and neighboring tissue in the larynx (voice box) or other parts of the throat.

• Larynx - valve structure between the trachea (windpipe) and the pharynx (the upper throat) that is the primary organ of voice production.

• Learning disabilities - childhood disorders characterized by difficulty with certain skills such as reading or writing in individuals with normal intelligence.

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M

• Magnetic resonance imaging (MRI) - a scanning procedure that uses radio waves and magnets to show images of body parts. This technique is generally used to visualize soft tissues.

• Mal de debarquement syndrome - rare balance disorder that causes a lasting sensation of motion sickness even when the cruise, airplane, or car ride is over; can also be accompanied by fatigue and difficulty concentrating.

• Mastoid - back portion of the temporal bone that contains the inner ear.

• Mastoid surgery - surgical procedure to remove infection from the mastoid bone.

• Meige syndrome - movement disorder that can involve excessive eye blinking (blepharospasm) with involuntary movements of the jaw muscles, lips, and tongue (oromandibular dystonia).

• Membranous labyrinth - fluid (endolymph)-filled network of bone-encased structures in the inner ear; necessary for normal hearing and balance.

• Ménière's disease - inner ear disorder that can affect both hearing and balance. It can cause episodes of vertigo, hearing loss, tinnitus, and the sensation of fullness in the ear.

• Meningitis - inflammation of the meninges, the membranes that envelop the brain and the spinal cord; may cause hearing loss or deafness.

• Middle ear - part of the ear that includes the eardrum and three tiny bones of the middle ear, ending at the round window that leads to the inner ear.

• Middle-ear implant - hearing aid consisting of an internal device that is surgically attached to one of the bones of the middle ear, thereby bypassing the ear canal and eardrum and strengthening the sound vibrations entering the inner ear. The implant is combined with an external audio processor unit that is worn behind the ear.

• Misarticulation - inaccurately produced speech sound (phoneme) or sounds.

• Mixed spasmodic dysphonia - sudden, involuntary muscle movements that cause vocal folds (formerly known as vocal cords) to open or close forcefully, making it difficult for them to vibrate and produce sound. (see also adductor spasmodic dysphonia and abductor spasmodic dysphonia).

• Morphology - units of language, including words and parts of speech.

• Motion sickness - dizziness, sweating, nausea, vomiting, and generalized discomfort experienced when an individual is in motion.

• Motor speech disorders - group of disorders caused by the inability to accurately produce speech sounds (phonemes) because of muscle weakness or incoordination or difficulty performing voluntary muscle movements.

N

• Neural plasticity - ability of the brain and/or certain parts of the nervous system to adapt to new conditions, such as an injury.

• Neural prostheses - devices that substitute for an injured or diseased part of the nervous system, such as the cochlear implant.

• Neural stimulation - to activate or energize a nerve through an external source.

• Neurofibromatosis type 1 (nf-1 von recklinghausen's) - group of inherited disorders in which noncancerous tumors grow on several nerves that may include the hearing nerve. The symptoms of nf-1 include coffee-colored spots on the skin, enlargement, deformation of bones, and neurofibromas.

• Neurofibromatosis type 2 - group of inherited disorders in which noncancerous tumors grow on several nerves that usually include the hearing nerve. The symptoms of nf-2 include tumors on the hearing nerve which can affect hearing and balance. Nf-2 may occur in the teenage years with hearing loss. Also see acoustic neurinoma.

• Neurogenic communication disorder - inability to exchange information with others because of hearing, speech, and/or language problems caused by impairment of the nervous system (brain or nerves).

• Neurogenic stuttering - disorder in which speech is disrupted by involuntary repetition and prolongation of sounds, syllables, words, or phrases; typically caused by  a stroke, head trauma, or other type of injury to the brain.

• Noise-induced hearing loss - hearing loss caused by exposure to harmful sounds, either very loud impulse sound(s) or repeated exposure to sounds over 90-decibel level over an extended period of time that damage the sensitive structures of the inner ear.

• Nonsyndromic hereditary hearing impairment - hearing loss or deafness that is inherited and is not associated with other inherited clinical characteristics.

O

• Odorant - substance that stimulates the sense of smell.

• Olfaction - the act of smelling.

• Olfactometer - device for estimating the intensity of the sense of smell.

• Open-set speech recognition - understanding speech without visual clues (speech reading).

• Otitis externa - inflammation of the outer part of the ear extending to the auditory canal.

• Otitis media - commonly called an ear infection, in which fluid is trapped behind the eardrum inside the middle ear. There are three main types: acute otitis media, otitis media with effusion, and chronic otitis media with effusion.

• Otitis media with effusion - ear infection in which fluid remains trapped behind the eardrum inside the middle ear after the infection is over. (see also acute otitis media and chronic otitis media with effusion.)

• Otoacoustic emissions - low-intensity sounds produced by the inner ear that can be quickly measured with a sensitive microphone placed in the ear canal.

• Otolaryngologist - physician/surgeon who specializes in diseases of the ears, nose, throat, and head and neck.

• Otologist - physician/surgeon who specializes in diseases of the ear.

• Otosclerosis - abnormal growth of bone of the inner ear. This bone prevents structures within the ear from working properly and causes hearing loss. For some people with otosclerosis, the hearing loss may become severe.

• Otoscope - tool that doctors use to look into the ear; has a cylindrical handle and a top with a lighted conical viewer at one end that inserts into the ear and a magnifying lens at the other end that enlarges the viewing area.

• Ototoxic drugs - drugs such as a special class of antibiotics, aminoglycoside antibiotics, that can damage the hearing and balance organs located in the inner ear for some individuals.

• Outer ear - external portion of the ear, consisting of the pinna, or auricle, and the ear canal.

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P

• Papillomavirus - group of viruses that can cause noncancerous wart-like tumors to grow on the surface of skin and internal organs such as the respiratory tract; can be life-threatening.

• Parosmia - any disease or perversion of the sense of smell, especially the subjective perception of odors that do not exist.

• Pendred syndrome - genetic disorder that causes early childhood hearing loss and sometimes progresses to total deafness; also often affects the thyroid gland and may affect balance.

• Perception (hearing) - process of knowing or being aware of information through the ear.

• Perilymph fistula - leakage of inner ear fluid to the middle ear that occurs without apparent cause or that is associated with head trauma, physical exertion, or barotrauma.

• Pervasive developmental disorders - disorders characterized by delays in several areas of development that may include socialization and communication.

• Pheromones - chemical substances secreted by an animal that elicit a specific behavioral or physiological response in another animal of the same species.

• Phonology - language-based sounds: in particular, phonemes, which are the units that make up words.

• Postlingually deafened - individual who becomes deaf after having acquired language.

• Pragmatics - how the context of language contributes to meaning.

• Prelingually deafened - individual who is either born deaf or who lost his or her hearing early in childhood, before acquiring language.

• Presbycusis - loss of hearing that gradually occurs because of changes in the inner ear in individuals as they grow older.

• Prosody - the rhythm, speed, pitch, and tone of spoken language.

• Psychogenic stuttering - sudden-onset disorder in which the fluency of speech is disrupted by involuntary repetition and prolongation of sounds, syllables, words, or phrases; arises in response to a psychological distress or trauma.

R

• Reading disorders - any of a group of problems characterized by difficulty using or understanding the symbol system for written language.

• Round window - membrane separating the middle ear and inner ear.

S

• Semantics - the study of meanings in language.

• Sensorineural hearing loss - hearing loss caused by damage to the sensory cells and/or nerve fibers of the inner ear.

• Sign language - method of communication for people who are deaf or hard of hearing in which hand movements, gestures, and facial expressions convey grammatical structure and meaning.

• Smell - to perceive odor or scent through stimuli affecting the olfactory nerves.

• Smell disorder - inability to perceive odors. It may be temporary, caused by a head cold or swelling or blockage of the nasal passages. It can be permanent when any part of the olfactory region is damaged by factors such as brain injury, tumor, disease, or chronic rhinitis.

• Sound vocalization - ability to produce voice.

• Spasmodic dysphonia - momentary disruption of voice caused by involuntary movements of one or more muscles of the larynx or voice box.

• Specific language impairment (sli) - difficulty with language or the organized-symbol system used for communication in the absence of problems such as mental retardation, hearing loss, or emotional disorders.

• Speech - spoken communication.

• Speech disorder - any defect or abnormality that prevents an individual from communicating by means of spoken words. Speech disorders may develop from nerve injury to the brain, muscular paralysis, structural defects, hysteria, or mental retardation.

• Speech processor - part of a cochlear implant that converts speech sounds into electrical impulses to stimulate the auditory nerve, allowing an individual to understand sound and speech.

• Speech-language pathologist - health professional trained to evaluate and treat people who have voice, speech, language, or swallowing disorders (including hearing impairment) that affect their ability to communicate.

• Stapedectomy - surgical procedure to improve hearing by removing a defective or damaged ear bone (the stapes) and replacing it with a tiny, piston-shaped artificial structure that permits sound waves to travel to the inner ear.

• Stereocilia - tiny hair-like structures on the tops of sensory hair cells in the inner ear. A group of stereocilia on one hair cell is also called a hair cell bundle.

• Stroke - also known as a cerebrovascular accident (cva); caused by a lack of blood to the brain, resulting in the sudden loss of speech, language, or the ability to move a body part, and, if severe enough, death.

• Stuttering - frequent repetition of words or parts of words that disrupts the smooth flow of speech.

• Sudden deafness - loss of hearing that occurs quickly due to such causes as explosion, a viral infection, or the use of some drugs.

• Swallowing disorders - any of a group of problems that interferes with the transfer of food from the mouth to the stomach.

• Syndromic hearing impairment - hearing loss or deafness that, along with other characteristics, is inherited or passed down through generations of a family.

• Syntax - sentence formation and structure.

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T

• Tactile - related to touch or the sense of touch.

• Tactile devices - mechanical instruments that make use of touch to help individuals who have certain disabilities, such as deaf-blindness, to communicate.

• Taste - sensation produced by a stimulus applied to the gustatory nerve endings in the tongue. The four tastes are salt, sour, sweet, and bitter. Some scientists indicate the existence of a fifth taste, described as savory.

• Taste buds - groups of cells located on the tongue that enable one to recognize different tastes.

• Taste disorder - inability to perceive different flavors. Taste disorders may result from poor oral hygiene, gum disease, hepatitis, or medicines and chemotherapeutic drugs. Taste disorders may also be neurological.

• Telecommunications relay service (trs) - operator service that allows people who are hearing-impaired or speech-impaired to place calls to standard telephone users via a keyboard or assistive device. (see also hearing carry-over and voice carry-over).

• Throat disorders - disorders or diseases of the larynx (voice box), pharynx, or esophagus.

• Thyroplasty - surgical technique to improve voice by altering the cartilages of the larynx, which houses the vocal folds (vocal cords), in order to change the position or length of the vocal folds. Also known as laryngeal framework surgery.

• Tinnitus - sensation of a ringing, roaring, or buzzing sound in the ears or head. It is often associated with many forms of hearing impairment and noise exposure.

• Tongue - large muscle on the floor of the mouth that manipulates food for chewing and swallowing. It is the main organ of taste, and assists in forming speech sounds.

• Touch - tactile sense; the sense by which contact with the skin or mucous membrane is experienced.

• Tourette syndrome - neurological disorder characterized by recurring movements and sounds (called tics).

• Tracheostomy - surgical opening into the trachea (windpipe) to help someone breathe who has an obstruction or swelling in the larynx (voice box) or upper throat or who has had the larynx surgically removed.

• Tympanic membrane (eardrum)- thin, cone-shaped and flexible structure that separates the external ear from the middle ear and transmits sound from outside the body to inside the ear.

• Tympanometry - technique that varies air pressure in the ear canal to test how well the middle-ear functions.

• Tympanoplasty - surgical repair of the eardrum (tympanic membrane) or bones of the middle ear.

U

• Umami - taste of substances such as l-glutamate salts (msg) that are found in foods like bouillon and other stocks.

• Usher syndrome - hereditary disease that affects hearing and vision and sometimes balance.

V

• Velocardiofacial syndrome - inherited disorder characterized by cleft palate (opening in the roof of the mouth), heart defects, characteristic facial appearance, minor learning problems, and speech and feeding problems.

• Vertigo - illusion of movement; a sensation as if the external world were revolving around an individual (objective vertigo) or as if the individual were revolving in space (subjective vertigo).

• Vestibular aqueducts - narrow, bony, fluid-filled canals that extend from the membranous labyrinth into the inner ear and skull.

• Vestibular labyrinth - sensory structure in the inner ear that helps control balance and the body's orientation in space.

• Vestibular neuronitis - irritation and swelling (inflammation) of the vestibular nerve that causes sudden dizziness; sometimes accompanied by nausea and vomiting, but not hearing loss.

• Vestibular system - system in the body that is responsible for maintaining balance, posture, and the body's orientation in space. This system also regulates locomotion and other movements and keeps objects in visual focus as the body moves.

• Vestibule - bony cavity of the inner ear.

• Vibrotactile aids - mechanical instruments that help individuals who are deaf to detect and interpret sound through the sense of touch.

• Vocal cords - see vocal folds

• Vocal fold paralysis - inability of one or both vocal folds (vocal cords) to move because of damage to the brain or nerves.

• Vocal folds (vocal cords) - muscularized folds of mucous membrane that extend from the larynx (voice box) wall. The folds are enclosed in elastic vocal ligament and muscle that control the tension and rate of vibration of the folds as air passes through them.

• Vocal nodule - small, noncancerous growth on the vocal folds (formerly known as vocal cords); among the most common of voice disorders directly related to misusing or overusing the voice

• Vocal polyp - noncancerous growth on the vocal folds (formerly known as vocal cords) similar to a vocal nodule but softer and more like a blister than a callous; can be caused by smoking, misusing or overusing the voice, or other factors. (see also vocal nodule.)

• Vocal tremor - trembling or shaking of one or more of the muscles of the larynx, resulting in an unsteady-sounding voice.

• Voice - sound produced by air passing out through the larynx and upper respiratory tract.

• Voice carry-over  (vco, also called hearing carry over)- type of call provided by a phone  service that allows a speech-impaired person who can hear to communicate with another party using an operator who speaks the caller’s typed messages.

• Voice disorders - group of problems involving abnormal pitch, loudness, or quality of the sound produced by the larynx (voice box).

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W

• Waardenburg syndrome - hereditary disorder that is characterized by hearing impairment, a white shock of hair and/or distinctive blue color to one or both eyes, and wide-set inner corners of the eyes. Balance problems are also associated with some types of waardenburg syndrome.

• Wernicke’s aphasia  (also known as receptive or fluent aphasia) - disorder in which someone can speak but can’t understand language in its written or spoken form; caused by damage to the medial temporal lobe of the brain.

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