Hearing loss, also known as hearing impairment, is a partial or total inability to hear. A deaf person has little to no hearing. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to learn spoken language and in adults it can create difficulties with social interaction and at work. In some people, particularly older people, hearing loss can result in loneliness. Hearing loss can be temporary or permanent.
|Other names||Hearing impaired, Hard of hearing; anakusis or anacusis is total deafness|
|The international symbol of deafness and hearing loss|
|Types||Conductive, sensorineural, and mixed hearing loss, central auditory dysfunction|
|Causes||Genetics, aging, exposure to noise, some infections, birth complications, trauma to the ear, certain medications or toxins|
|Prevention||Immunization, proper care around pregnancy, avoiding loud noise, avoiding certain medications|
|Treatment||Hearing aids, sign language, cochlear implants, subtitles|
|Frequency||1.33 billion / 18.5% (2015)|
Hearing loss may be caused by a number of factors, including: genetics, ageing, exposure to noise, some infections, birth complications, trauma to the ear, and certain medications or toxins. A common condition that results in hearing loss is chronic ear infections. Certain infections during pregnancy, such as cytomegalovirus, syphilis and rubella, may also cause hearing loss in the child. Hearing loss is diagnosed when hearing testing finds that a person is unable to hear 25 decibels in at least one ear. Testing for poor hearing is recommended for all newborns. Hearing loss can be categorized as mild (25 to 40 dB), moderate (41 to 55 dB), moderate-severe (56 to 70 dB), severe (71 to 90 dB), or profound (greater than 90 dB). There are three main types of hearing loss: conductive hearing loss, sensorineural hearing loss, and mixed hearing loss.
About half of hearing loss globally is preventable through public health measures. Such practices include immunization, proper care around pregnancy, avoiding loud noise, and avoiding certain medications. The World Health Organization recommends that young people limit the use of personal audio players to an hour a day in an effort to limit exposure to noise. Early identification and support are particularly important in children. For many hearing aids, sign language, cochlear implants and subtitles are useful. Lip reading is another useful skill some develop. Access to hearing aids, however, is limited in many areas of the world.
As of 2013 hearing loss affects about 1.1 billion people to some degree. It causes disability in 5% (360 to 538 million) and moderate to severe disability in 124 million people. Of those with moderate to severe disability 108 million live in low and middle income countries. Of those with hearing loss, it began during childhood for 65 million. Those who use sign language and are members of Deaf culture see themselves as having a difference rather than an illness. Most members of Deaf culture oppose attempts to cure deafness and some within this community view cochlear implants with concern as they have the potential to eliminate their culture. The term hearing impairment is often viewed negatively as it emphasises what people cannot do.
- Hearing loss exists when there is diminished acuity to sounds normally heard. The terms hearing impaired or hard of hearing are usually reserved for people who have relative inability to hear sound in the speech frequencies. The severity of a hearing loss is categorized according to the increase in intensity of sound above the usual level necessary before the listener can detect it.
- Deafness is defined as a degree of loss such that a person is unable to understand speech even in the presence of amplification. In profound deafness, even the highest intensity sounds produced by an audiometer (an instrument used to measure hearing by producing pure tone sounds through a range of frequencies) may not be detected. In total deafness, no sounds at all, regardless of amplification or method of production, are heard.
- Speech perception – Another aspect of hearing involves the perceived clarity of a word rather than the intensity of sound made by the word. In humans, that aspect is usually measured by tests of speech discrimination. These tests measure one's ability to understand speech, not to merely detect sound. There are very rare types of hearing loss which affect speech discrimination alone. One example is auditory neuropathy, a variety of hearing loss in which the outer hair cells of the cochlea are intact and functioning, but sound information is not faithfully transmitted to the auditory nerve and brain properly.
Use of the terms "hearing impaired", "deaf-mute", or "deaf and dumb" to describe deaf and hard of hearing people is discouraged by advocacy organizations as they are offensive to many deaf and hard of hearing people.
Human hearing extends in frequency from 20–20,000 Hz, and in intensity from 0 dB to 120 dB HL or more. 0 dB does not represent absence of sound, but rather the softest sound an average unimpaired human ear can hear; some people can hear down to −5 or even −10 dB. Sound is generally uncomfortably loud above 90 dB and 115 dB represents the threshold of pain. The ear does not hear all frequencies equally well; hearing sensitivity peaks around 3000 Hz. There are many qualities of human hearing besides frequency range and intensity that cannot easily be measured quantitatively. But for many practical purposes, normal hearing is defined by a frequency versus intensity graph, or audiogram, charting sensitivity thresholds of hearing at defined frequencies. Because of the cumulative impact of age and exposure to noise and other acoustic insults, 'typical' hearing may not be normal.
Signs and symptomsEdit
- difficulty using the telephone
- loss of directionality of sound
- difficulty understanding speech, especially of children and women whose voices are of a higher frequency.
- difficulty understanding speech in the presence of background noise (cocktail party effect)
- sounds or speech becoming dull, muffled or attenuated
- need for increased volume on television, radio, music and other audio sources
Hearing loss is sensory, but may have accompanying symptoms:
- pain or pressure in the ears
- a blocked feeling
There may also be accompanying secondary symptoms:
- hyperacusis, heightened sensitivity with accompanying auditory pain to certain intensities and frequencies of sound, sometimes defined as "auditory recruitment"
- tinnitus, ringing, buzzing, hissing or other sounds in the ear when no external sound is present
- vertigo and disequilibrium
- tympanophonia, also known as autophonia, abnormal hearing of one's own voice and respiratory sounds, usually as a result of a patulous (a constantly open) eustachian tube or dehiscent superior semicircular canals
- disturbances of facial movement (indicating a possible tumour or stroke) or in persons with Bell's Palsy
Hearing loss has multiple causes, including ageing, genetics, perinatal problems and acquired causes like noise and disease. For some kinds of hearing loss the cause may be classified as of unknown cause.
There is a progressive loss of ability to hear high frequencies with aging known as presbycusis. For men, this can start as early as 25 and women at 30. Although genetically variable it is a normal concomitant of ageing and is distinct from hearing losses caused by noise exposure, toxins or disease agents. Common conditions that can increase the risk of hearing loss in elderly people are high blood pressure, diabetes or the use of certain medications harmful to the ear. While everyone loses hearing with age, the amount and type of hearing loss is variable.
The examples and perspective in this section may not represent a worldwide view of the subject. (December 2015) (Learn how and when to remove this template message)
Noise exposure is the cause of approximately half of all cases of hearing loss, causing some degree of problems in 5% of the population globally. The National Institute for Occupational Safety and Health (NIOSH) recognizes that the majority of hearing loss is not due to age, but due to noise exposure. By correcting for age in assessing hearing, one tends to overestimate the hearing loss due to noise for some and underestimate it for others.
Hearing loss due to noise may be temporary, called a 'temporary threshold shift', a reduced sensitivity to sound over a wide frequency range resulting from exposure to a brief but very loud noise like a gunshot, firecracker, jet engine, jackhammer, etc. or to exposure to loud sound over a few hours such as during a pop concert or nightclub session. Recovery of hearing is usually within 24 hours, but may take up to a week. Both constant exposure to loud sounds (85 dB(A) or above) and one-time exposure to extremely loud sounds (120 dB(A) or above) may cause permanent hearing loss.
Noise-induced hearing loss (NIHL) typically manifests as elevated hearing thresholds (i.e. less sensitivity or muting) between 3000 and 6000 Hz, centred at 4000 Hz. As noise damage progresses, damage spreads to affect lower and higher frequencies. On an audiogram, the resulting configuration has a distinctive notch, called a 'noise' notch. As ageing and other effects contribute to higher frequency loss (6–8 kHz on an audiogram), this notch may be obscured and entirely disappear.
Various governmental, industry and standards organizations set noise standards.
The U.S. Environmental Protection Agency has identified the level of 70 dB(A) (40% louder to twice as loud as normal conversation; typical level of TV, radio, stereo; city street noise) for 24‑hour exposure as the level necessary to protect the public from hearing loss and other disruptive effects from noise, such as sleep disturbance, stress-related problems, learning detriment, etc. Noise levels are typically in the 65 to 75 dB (A) range for those living near airports of freeways and may result in hearing damage if sufficient time is spent outdoors.
Louder sounds cause damage in a shorter period of time. Estimation of a "safe" duration of exposure is possible using an exchange rate of 3 dB. As 3 dB represents a doubling of the intensity of sound, duration of exposure must be cut in half to maintain the same energy dose. For workplace noise regulation, the "safe" daily exposure amount at 85 dB A, known as an exposure action value, is 8 hours, while the "safe" exposure at 91 dB(A) is only 2 hours. Different standards use exposure action values between 80dBA and 90dBA. Note that for some people, sound may be damaging at even lower levels than 85 dB A. Exposures to other ototoxins (such as pesticides, some medications including chemotherapy agents, solvents, etc.) can lead to greater susceptibility to noise damage, as well as causing its own damage. This is called a synergistic interaction. Since noise damage is cumulative over long periods of time, persons who are exposed to non-workplace noise, like recreational activities or environmental noise, may have compounding damage from all sources.
Some national and international organizations and agencies use an exchange rate of 4 dB or 5 dB. While these exchange rates may indicate a wider zone of comfort or safety, they can significantly underestimate the damage caused by loud noise. For example, at 100 dB (nightclub music level), a 3 dB exchange rate would limit exposure to 15 minutes; the 5 dB exchange rate allows an hour.
Many people are unaware of the presence of environmental sound at damaging levels, or of the level at which sound becomes harmful. Common sources of damaging noise levels include car stereos, children's toys, motor vehicles, crowds, lawn and maintenance equipment, power tools, gun use, musical instruments, and even hair dryers. Noise damage is cumulative; all sources of damage must be considered to assess risk. If one is exposed to loud sound (including music) at high levels or for extended durations (85 dB A or greater), then hearing loss will occur. Sound intensity (sound energy, or propensity to cause damage to the ears) increases dramatically with proximity according to an inverse square law: halving the distance to the sound quadruples the sound intensity.
In the USA, 12.5% of children aged 6–19 years have permanent hearing damage from excessive noise exposure. The World Health Organization estimates that half of those between 12 and 35 are at risk from using personal audio devices that are too loud.
Hearing loss due to noise has been described as primarily a condition of modern society. In preindustrial times, humans had far less exposure to loud sounds. Studies of primitive peoples indicate that much of what has been attributed to age-related hearing loss may be long term cumulative damage from all sources, especially noise. People living in preindustrial societies have considerably less hearing loss than similar populations living in modern society. Among primitive people who have migrated into modern society, hearing loss is proportional to the number of years spent in modern society. Military service in World War II, the Korean War, and the Vietnam War, has likely also caused hearing loss in large numbers of men from those generations, though proving that hearing loss was a direct result of military service is problematic without entry and exit audiograms.
Hearing loss in adolescents may be caused by loud noise from toys, music by headphones, and concerts or events. In 2017, the Centers for Disease Control and Prevention brought their researchers together with experts from the World Health Organization and academia to examine the risk of hearing loss from excessive noise exposure in and outside the workplace in different age groups, as well as actions being taken to reduce the burden of the condition. A summary report was published in 2018.
Hearing loss can be inherited. Around 75–80% of all these cases are inherited by recessive genes, 20–25% are inherited by dominant genes, 1–2% are inherited by X-linked patterns, and fewer than 1% are inherited by mitochondrial inheritance.
When looking at the genetics of deafness, there are 2 different forms, syndromic and nonsyndromic. Syndromic deafness occurs when there are other signs or medical problems aside from deafness in an individual. This accounts for around 30% of deaf individuals who are deaf from a genetic standpoint. Nonsyndromic deafness occurs when there are no other signs or medical problems associated with an individual other than deafness. From a genetic standpoint, this accounts for the other 70% of cases, and represents the majority of hereditary hearing loss. Syndromic cases occur with disorders such as Usher syndrome, Stickler syndrome, Waardenburg syndrome, Alport's syndrome, and neurofibromatosis type 2. These are diseases that have deafness as one of the symptoms or as a common feature associated with it. Many of the genetic mutations giving rise to syndromic deafness have been identified. In nonsyndromic cases, where deafness is the only finding, it is more difficult to identify the genetic mutation although some have been discovered.
- Gene mapping has identified the genetic locations for several nonsyndromic dominant (DFNA#) and recessive (DFNB#) forms of deafness. The first gene mapped for non-syndromic deafness, DFNA1, involves a splice site mutation in the formin related homolog diaphanous 1 (DIAPH1). A single base change in a large Costa Rican family was identified as causative in a rare form of low frequency onset progressive hearing loss with autosomal dominant inheritance exhibiting variable age of onset and complete penetrance by age 30. The most common type of congenital hearing loss in developed countries is DFNB1, also known as connexin 26 deafness or GJB2-related deafness.
- The most common dominant syndromic forms of hearing loss include Stickler syndrome and Waardenburg syndrome.
- The most common recessive syndromic forms of hearing loss are Pendred syndrome and Usher syndrome.
- The congenital defect microtia, deformed or unformed outer ear, can be associated with partial or complete conductive deafness, depending upon the severity of the deformity and whether the middle ear is also affected. It can also be associated with abnormalities of the inner ear giving rise to an additional sensorineural component to the hearing loss (mixed deafness).
- Dozens of additional genes for nonsyndromic deafness have been identified.
- Fetal alcohol spectrum disorders are reported to cause hearing loss in up to 64% of infants born to alcoholic mothers, from the ototoxic effect on the developing fetus plus malnutrition during pregnancy from the excess alcohol intake.
- Premature birth can be associated with sensorineural hearing loss because of an increased risk of hypoxia, hyperbilirubinaemia, ototoxic medication and infection as well as noise exposure in the neonatal units. The risk of hearing loss is greatest for those weighing less than 1500 g at birth.
- Auditory neuropathy a disorder of poor speech perception even though the tympanic membrane, middle ear structures, and cochlear nerve are intact. People with auditory neuropathy may have normal hearing or hearing loss ranging from mild to severe.
- Inherited disorders
- People with Down syndrome are more likely to have hearing loss. This is usually due to middle ear effusions in childhood but towards the end of the second decade they may develop a high frequency sensorineural hearing loss which can get progressively worse with time.
- Charcot–Marie–Tooth disease variant 1E (CMT1E) is noted for demyelinating in addition to deafness.
- Autoimmune disease is recognized as a cause for cochlear damage. Although rare, it is possible for autoimmune processes to target the cochlea specifically as a first presentation. Granulomatosis with polyangiitis is one of the autoimmune conditions that may precipitate hearing loss. Cogan's syndrome commonly presents with hearing loss.
- Multiple sclerosis can have an effect on hearing as well. Multiple sclerosis, or MS, is an autoimmune disease where the immune system attacks the myelin sheath, a covering that protects the nerves. If the auditory nerve becomes damaged, the affected person will become completely deaf in one or both ears. There is no cure for MS.
- Meningitis may damage the auditory nerve or the cochlea.
- Cholesteatoma is a (acquired or congenital) benign collection of squamous epithelial cells within the middle ear. Acquired cholesteatomas are commonly caused by repeated middle ear infections
- Otosclerosis is a condition that can cause fixation of the stapes (or stirrup) in the middle ear preventing its movement and causing a conductive hearing loss.
- Perilymph fistula – a microtear in either the round or oval window (membranes separating the middle and inner ear) of the cochlea causing perilymph to leak into the middle ear. This usually occurs as a consequence of trauma, including barotrauma, and can give rise to vertigo as well as hearing loss.
- Ménière's disease (endolymphatic hydrops) occurs when there is an elevated pressure in the endolymph in the cochlea. Its symptoms include fluctuating low frequency hearing loss, aural fullness, tinnitus, and dizziness lasting for hours
- Recurring ear infections or concomitant secondary infections (such as bacterial infection subsequent to viral infection) can result in hearing loss
- Strokes – Depending on what blood vessels are affected by the stroke, one of the symptoms can be deafness
- Superior semicircular canal dehiscence, a gap in the bone cover above the inner ear, can lead to low-frequency conductive hearing loss, autophony and vertigo.
- Syndromic hearing loss can be either conductive or sensorineural. It occurs with abnormalities in other parts of the bodies. Examples include Pierre Robin, Treacher-Collins, Retinitis Pigmentosa, Pedreds, and Turners syndrome, among others.
- Syphilis is commonly transmitted from pregnant women to their fetuses, and about a third of infected children will eventually become deaf.
- Vestibular schwannoma, erroneously known as Acoustic neuromas, and other types of brain tumors can cause hearing loss by infringement of the tumor on the vestibulocochlear nerve
- Viral infections of the ear can cause sensorineural hearing loss usually as the consequence of a labyrinthitis. The person may be generally unwell at the time.
- Measles may cause auditory nerve damage but usually gives rise to a chronic middle ear problem giving rise to a mixed hearing loss.
- Mumps (Epidemic parotitis) may result in profound sensorineural hearing loss (90 dB or more), unilateral (one ear) or bilateral (both ears).
- congenital rubella (also called German measles) syndrome, can cause deafness in newborns
- several varieties of herpes viruses that cause other diseases can also infect the ear, and can result in hearing loss: congenital infection with cytomegalovirus is responsible for deafness in newborn children and also progressive sensorineural hearing loss in childhood; herpes simplex type 1, oral herpes associated with cold sores; Epstein Barr virus that causes mononucleosis; varicella zoster oticus that causes facial paralysis (Ramsay Hunt syndrome)
- People with HIV/AIDS may develop hearing problems due to medications they take for the disease, the HIV virus, or due to an increased rate of other infections.
- West Nile virus, which can cause a variety of neurological disorders, can also cause hearing loss by attacking the auditory nerve.
Some medications may reversibly affect hearing. These medications are considered ototoxic. This includes loop diuretics such as furosemide and bumetanide, non-steroidal anti-inflammatory drugs (NSAIDs) both over-the-counter (aspirin, ibuprofen, naproxen) as well as prescription (celecoxib, diclofenac, etc.), paracetamol, quinine, and macrolide antibiotics. The link between NSAIDs and hearing loss tends to be greater in women, especially those who take ibuprofen six or more times a week. Others may cause permanent hearing loss. The most important group is the aminoglycosides (main member gentamicin) and platinum based chemotherapeutics such as cisplatin and carboplatin.
On October 18, 2007, the U.S. Food and Drug Administration (FDA) announced that a warning about possible sudden hearing loss would be added to drug labels of PDE5 inhibitors, which are used for erectile dysfunction.
Audiologic monitoring for ototoxicity allows for the (1) early detection of changes to hearing status presumably attributed to a drug/treatment regime so that changes in the drug regimen may be considered, and (2) audiologic intervention when handicapping hearing impairment has occurred.
In addition to medications, hearing loss can also result from specific chemicals in the environment: metals, such as lead; solvents, such as toluene (found in crude oil, gasoline and automobile exhaust, for example); and asphyxiants. Combined with noise, these ototoxic chemicals have an additive effect on a person’s hearing loss.
Hearing loss due to chemicals starts in the high frequency range and is irreversible. It damages the cochlea with lesions and degrades central portions of the auditory system. For some ototoxic chemical exposures, particularly styrene, the risk of hearing loss can be higher than being exposed to noise alone. The effects is greatest when the combined exposure include impulse noise.
- Heavy metals
- Pesticides and herbicides – The evidence is weak regarding association between herbicides and hearing loss; hearing loss in such circumstances may be due to concommitant exposure to insecticides.
A 2018 informational bulletin by the US Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) introduces the issue, provides examples of ototoxic chemicals, lists the industries and occupations at risk and provides prevention information.
There can be damage either to the ear, whether the external or middle ear, to the cochlea, or to the brain centers that process the aural information conveyed by the ears. Damage to the middle ear may include fracture and discontinuity of the ossicular chain. Damage to the inner ear (cochlea) may be caused by temporal bone fracture. People who sustain head injury are especially vulnerable to hearing loss or tinnitus, either temporary or permanent.
Sound waves reach the outer ear and are conducted down the ear canal to the eardrum, causing it to vibrate. The vibrations are transferred by the 3 tiny ear bones of the middle ear to the fluid in the inner ear. The fluid moves hair cells (stereocilia), and their movement generates nerve impulses which are then taken to the brain by the cochlear nerve. The auditory nerve takes the impulses to the brainstem, which sends the impulses to the midbrain. Finally, the signal goes to the auditory cortex of the temporal lobe to be interpreted as sound.
Older people may lose their hearing from long exposure to noise, changes in the inner ear, changes in the middle ear, or from changes along the nerves from the ear to the brain.
Identification of a hearing loss is usually conducted by a general practitioner medical doctor, otolaryngologist, certified and licensed audiologist, school or industrial audiometrist, or other audiometric technician. Diagnosis of the cause of a hearing loss is carried out by a specialist physician (audiovestibular physician) or otorhinolaryngologist.
A case history (usually a written form, with questionnaire) can provide valuable information about the context of the hearing loss, and indicate what kind of diagnostic procedures to employ. Case history will include such items as:
- major concern
- birth and pregnancy information
- medical history
- development history
- family history
- workplace environment
- home environment
- otoscopy, visual examination of the outer ear, ear canal, eardrum, and middle ear (through the translucent eardrum) using an optical instrument inserted into the ear canal called an otoscope
- differential testing – the Weber, Rinne, Bing and Schwabach tests are simple manual tests of auditory function conducted with a low frequency (usually 512 Hz) tuning fork that can provide a quick indication of type of hearing loss: unilateral/bilateral, conductive, or other
In case of infection or inflammation, blood or other body fluids may be submitted for laboratory analysis.
Hearing loss is generally measured by playing generated or recorded sounds, and determining whether the person can hear them. Hearing sensitivity varies according to the frequency of sounds. To take this into account, hearing sensitivity can be measured for a range of frequencies and plotted on an audiogram.
Another method for quantifying hearing loss is a speech-in-noise test. As the name implies, a speech-in-noise test gives an indication of how well one can understand speech in a noisy environment. A person with a hearing loss will often be less able to understand speech, especially in noisy conditions. This is especially true for people who have a sensorineural loss – which is by far the most common type of hearing loss. As such, speech-in-noise tests can provide valuable information about a person's hearing ability, and can be used to detect the presence of a sensorineural hearing loss. A recently developed digit-triple speech-in-noise test may be a more efficient screening test.
Otoacoustic emissions test is an objective hearing test that may be administered to toddlers and children too young to cooperate in a conventional hearing test. The test is also useful in older children and adults and is an important measure in diagnosing auditory neuropathy described above.
Auditory brainstem response testing is an electrophysiological test used to test for hearing deficits caused by pathology within the ear, the cochlear nerve and also within the brainstem. This test can be used to identify delay in the conduction of neural impulses due to tumours or inflammation but can also be an objective test of hearing thresholds. Other electrophysiological tests, such as cortical evoked responses, can look at the hearing pathway up to the level of the auditory cortex.
MRI and CT scans can be useful to identify the pathology of many causes of hearing loss. They are only needed in selected cases.
Hearing loss is categorized by type, severity, and configuration. Furthermore, a hearing loss may exist in only one ear (unilateral) or in both ears (bilateral). Hearing loss can be temporary or permanent, sudden or progressive.
The severity of a hearing loss is ranked according to ranges of nominal thresholds in which a sound must be so it can be detected by an individual. It is measured in decibels of hearing loss, or dB HL. The measurement of hearing loss in an individual is conducted over several frequencies, mostly 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz. The hearing loss of the individual is the average of the hearing loss values over the different frequencies. Hearing loss can be ranked differently according to different organisations; and so, in different countries different systems are in use.
Hearing loss may be ranked as slight, mild, moderate, moderately severe, severe or profound as defined below:[medical citation needed]
- Slight: between 16 and 25 dB HL
- for adults: between 26 and 40 dB HL
- for children: between 20 and 40 dB HL
- Moderate: between 41 and 54 dB HL
- Moderately severe: between 55 and 70 dB HL
- Severe: between 71 and 90 dB HL
- Profound: 91 dB HL or greater
- Totally deaf: Have no hearing at all. This is called anacusis.
The 'Audiometric Classifications of Hearing Impairment' according to the International Bureau Audiophonology (BIAP) in Belgium is as follows:
- Normal or subnormal hearing: average tone loss is equal or below 20 dB HL
- Mild hearing loss: average tone loss between 21 and 40 dB HL
- Moderate hearing loss
- First degree: average tone loss between 41 and 55 dB HL
- Second degree: average tone loss between 56 and 70 dB HL
- Severe hearing loss
- First degree: average tone loss between 71 and 80 dB HL
- Second degree: average tone loss between 81 and 90 dB HL
- Very severe hearing loss
- First degree: average tone loss between 91 and 100 dB HL
- Second degree: average tone loss between 101 and 110 dB HL
- Third degree: average tone loss between 111 and 119 dB HL
- Total hearing loss or Cophosis: average tone loss is equal or more than 120 dB HL
Hearing loss may affect one or both ears. If both ears are affected, then one ear may be more affected than the other. Thus it is possible, for example, to have normal hearing in one ear and none at all in the other, or to have mild hearing loss in one ear and moderate hearing loss in the other.
For certain legal purposes such as insurance claims, hearing loss is described in terms of percentages. Given that hearing loss can vary by frequency and that audiograms are plotted with a logarithmic scale, the idea of a percentage of hearing loss is somewhat arbitrary, but where decibels of loss are converted via a legally recognized formula, it is possible to calculate a standardized "percentage of hearing loss", which is suitable for legal purposes only.
There are three main types of hearing loss, conductive hearing loss, sensorineural hearing loss. Combinations of conductive and sensorineural hearing losses are called a mixed hearing loss. An additional problem which is increasingly recognised is auditory processing disorder which is not a hearing loss as such but a difficulty perceiving sound.
- Conductive hearing loss
Conductive hearing loss is present when the sound is not reaching the inner ear, the cochlea. This can be due to external ear canal malformation, dysfunction of the eardrum or malfunction of the bones of the middle ear. The eardrum may show defects from small to total resulting in hearing loss of different degree. Scar tissue after ear infections may also make the eardrum dysfunction as well as when it is retracted and adherent to the medial part of the middle ear.
Dysfunction of the three small bones of the middle ear – malleus, incus, and stapes – may cause conductive hearing loss. The mobility of the ossicles may be impaired for different reasons including a boney disorder of the ossicles called otosclerosis and disruption of the ossicular chain due to trauma, infection or ankylosis may also cause hearing loss.
- Sensorineural hearing loss
Sensorineural hearing loss is one caused by dysfunction of the inner ear, the cochlea or the nerve that transmits the impulses from the cochlea to the hearing centre in the brain. The most common reason for sensorineural hearing loss is damage to the hair cells in the cochlea. Depending on the definition it could be estimated that more than 50% of the population over the age of 70 has impaired hearing.
- Central deafness
Damage to the brain can lead to a central deafness. The peripheral ear and the auditory nerve may function well but the central connections are damaged by tumour, trauma or other disease and the patient is unable to process speech information.
- Mixed hearing loss
Mixed hearing loss is a combination of conductive and sensorineural hearing loss. Chronic ear infection (a fairly common diagnosis) can cause a defective ear drum or middle-ear ossicle damages, or both. In addition to the conductive loss, a sensory component may be present.
- Central auditory processing disorder
This is not an actual hearing loss but gives rise to significant difficulties in hearing. One kind of auditory processing disorder is King-Kopetzky syndrome, which is characterized by an inability to process out background noise in noisy environments despite normal performance on traditional hearing tests. An auditory processing disorders is sometimes linked to language disorders in persons of all ages.
The shape of an audiogram shows the relative configuration of the hearing loss, such as a Carhart notch for otosclerosis, 'noise' notch for noise-induced damage, high frequency rolloff for presbycusis, or a flat audiogram for conductive hearing loss. In conjunction with speech audiometry, it may indicate central auditory processing disorder, or the presence of a schwannoma or other tumor. There are four general configurations of hearing loss:
1. Flat: thresholds essentially equal across test frequencies.
2. Sloping: lower (better) thresholds in low-frequency regions and higher (poorer) thresholds in high-frequency regions.
3. Rising: higher (poorer) thresholds in low-frequency regions and lower (better) thresholds in higher-frequency regions.
4. Trough-shaped ("cookie-bite" or "U" shaped): greatest hearing loss in the mid-frequency range, with lower (better) thresholds in low- and high-frequency regions.
Unilateral and bilateralEdit
People with unilateral hearing loss or single-sided deafness (SSD) have difficulty in:
- hearing conversation on their impaired side
- localizing sound
- understanding speech in the presence of background noise.
In quiet conditions, speech discrimination is approximately the same for normal hearing and those with unilateral deafness; however, in noisy environments speech discrimination varies individually and ranges from mild to severe.
One reason for the hearing problems these patients often experience is due to the head shadow effect. Newborn children with no hearing on one side but one normal ear could still have problems. Speech development could be delayed and difficulties to concentrate in school are common. More children with unilateral hearing loss have to repeat classes than their peers. Taking part in social activities could be a problem. Early aiding is therefore of utmost importance.
It is estimated that half of cases of hearing loss are preventable. About 60% of hearing loss in children under the age of 15 can be avoided. A number of preventative strategies are effective including: immunization against rubella to prevent congenital rubella syndrome, immunization against H. influenza and S. pneumoniae to reduce cases of meningitis, and avoiding or protecting against excessive noise exposure. The World Health Organization also recommends immunization against measles, mumps, and meningitis, efforts to prevent premature birth, and avoidance of certain medication as prevention.
Noise exposure is the most significant risk factor for noise-induced hearing loss that can be prevented. Different programs exist for specific populations such as school-age children, adolescents and workers. Education regarding noise exposure increases the use of hearing protectors. The use of antioxidants is being studied for the prevention of noise-induced hearing loss, particularly for scenarios in which noise exposure cannot be reduced, such as during military operations.
Workplace noise regulationEdit
Noise is widely recognized as an occupational hazard. In the United States, the National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA) work together to provide standards and enforcement on workplace noise levels. The hierarchy of hazard controls demonstrates the different levels of controls to reduce or eliminate exposure to noise and prevent hearing loss, including engineering controls and personal protective equipment (PPE). Other programs and initiative have been created to prevent hearing loss in the workplace. For example, the Safe-in-Sound Award was created to recognize organizations that can demonstrate results of successful noise control and other interventions. Additionally, the Buy Quiet program was created to encourage employers to purchase quieter machinery and tools. By purchasing less noisy power tools like those found on the NIOSH Power Tools Database and limiting exposure to ototoxic chemicals, great strides can be made in preventing hearing loss.
Companies can also provide personal hearing protector devices tailored to both the worker and type of employment. Some hearing protectors universally block out all noise, and some allow for certain noises to be heard. Workers are more likely to wear hearing protector devices when they are properly fitted.
Often interventions to prevent noise-induced hearing loss have many components. A 2017 Cochrane review found that stricter legislation might reduce noise levels. Providing workers with information on their noise exposure levels was not shown to decrease exposure to noise. Ear protection, if used correctly, can reduce noise to safer levels, but often, providing them is not sufficient to prevent hearing loss. Engineering noise out and other solutions such as proper maintenance of equipment can lead to noise reduction, but further field studies on resulting noise exposures following such interventions are needed. Other possible solutions include improved enforcement of existing legislation and better implementation of well-designed prevention programmes, which have not yet been proven conclusively to be effective. The conclusion of the Cochrane Review was that further research could modify what is now regarding the effectiveness of the evaluated interventions.
- When they enter school
- At ages 6, 8, and 10
- At least once during middle school
- At least once during high school
While the American College of Physicians indicated that there is not enough evidence to determine the utility of screening in adults over 50 years old who do not have any symptoms, the American Language, Speech Pathology and Hearing Association recommends that adults should be screened at least every decade through age 50 and at 3-year intervals thereafter, to minimize the detrimental effects of the untreated condition on quality of life. For the same reason, the US Office of Disease Prevention and Health Promotion included as one of Healthy People 2020 objectives: to increase the proportion of persons who have had a hearing examination.
Management depend on the specific cause if known as well as the extent, type and configuration of the hearing loss. Most hearing loss, that resulting from age and noise, is progressive and irreversible, and there are currently no approved or recommended treatments; management is by hearing aid. A few specific kinds of hearing loss are amenable to surgical treatment. In other cases, treatment is addressed to underlying pathologies, but any hearing loss incurred may be permanent.
Should a deaf or hard of hearing individual seek the use of additional hearing resources, there are a variety of devices that have the potential to aid hearing. However, not every deaf or hard of hearing person finds this beneficial or necessary. There are other numerous resources and technological advancements that support deaf and hard of hearing people in a variety of ways.
Globally, hearing loss affects about 10% of the population to some degree. It caused moderate to severe disability in 124.2 million people as of 2004 (107.9 million of whom are in low and middle income countries). Of these 65 million acquired the condition during childhood. At birth ~3 per 1000 in developed countries and more than 6 per 1000 in developing countries have hearing problems.
Hearing loss increases with age. In those between 20 and 35 rates of hearing loss are 3% while in those 44 to 55 it is 11% and in those 65 to 85 it is 43%.
A 2017 report by the World Health Organization estimated the costs of unaddressed hearing loss and the cost-effectiveness of interventions, for the health-care sector, for the education sector and as broad societal costs. Globally, the annual cost of unaddressed hearing loss was estimated to be in the range of $750–790 billion international dollars.
Data from the United States in 2011-2012 found that rates of hearing loss has declined among adults aged 20 to 69 years, when compared with the results from an earlier time period (1999-2004). It also found that adult hearing loss is associated with increasing age, sex, race/ethnicity, educational level, and noise exposure.
Nearly one in four adults had audiometric results suggesting noise-induced hearing loss. Almost one in four adults who reported excellent or good hearing had a similar pattern (5.5% on both sides and 18% on one side). Among people who reported exposure to loud noise at work, almost one third had such changes.
Abbé Charles-Michel de l'Épée opened the first school for the deaf in Paris at the deaf school. The American Thomas Gallaudet witnessed a demonstration of deaf teaching skills from Épée's successor Abbé Sicard and two of the school's deaf faculty members, Laurent Clerc and Jean Massieu; accompanied by Clerc, he returned to the United States, where in 1817 they founded American School for the Deaf in Hartford, Connecticut. American Sign Language (ASL) started to evolve from primarily French Sign Language (LSF), and other outside influences.
Society and cultureEdit
After language acquisitionEdit
Post-lingual deafness is hearing loss that is sustained after the acquisition of language, which can occur due to disease, trauma, or as a side-effect of a medicine. Typically, hearing loss is gradual and often detected by family and friends of affected individuals long before the patients themselves will acknowledge the disability. Post-lingual deafness is far more common than pre-lingual deafness. Those who lose their hearing later in life, such as in late adolescence or adulthood, face their own challenges, living with the adaptations that allow them to live independently.
Before language acquisitionEdit
Prelingual deafness is profound hearing loss that is sustained before the acquisition of language, which can occur due to a congenital condition or through hearing loss before birth or in early infancy. Prelingual deafness impairs an individual's ability to acquire a spoken language in children, but deaf children can acquire spoken language through support from cochlear implants (sometimes combined with hearing aids). Non-signing (hearing) parents of deaf babies (90-95% of cases) usually go with oral approach without the support of sign language as the these families lack previous experience with sign language and cannot competently provide it to their children. Unfortunately, this may in some rare cases (late implantation or not sufficient benefit from cochlear implants) bring the risk of language deprivation for the deaf baby because the deaf baby wouldn't have a sign language if the child is unable to acquire spoken language successfully. The 5-10% of cases of deaf babies born into signing families have the potential of age-appropriate development of language due to early exposure to sign language by sign-competent parents, thus they have the potential to meet language milestones, but in sign language in lieu of spoken language.
Views of managementEdit
There has been considerable controversy within the culturally deaf community over cochlear implants. For the most part, there is little objection to those who lost their hearing later in life, or culturally deaf adults choosing to be fitted with a cochlear implant.
Many in the deaf community strongly object to a deaf child being fitted with a cochlear implant (often on the advice of an audiologist); new parents may not have sufficient information on raising deaf children and placed in an oral-only program that emphasizes the ability to speak and listen over other forms of communication such as sign language or total communication. Many deaf people view cochlear implants and other hearing devices as confusing to one's identity. They feel a deaf person will never be a hearing person and therefore would be trying to fit into a way of living that is not their own. Other concerns include loss of deaf culture and identity and limitations on hearing restoration.
Jack Gannon, a professor at Gallaudet University, said this about Deaf culture: "Deaf culture is a set of learned behaviors and perceptions that shape the values and norms of deaf people based on their shared or common experiences." Some doctors believe that being deaf makes a person more social. Bill Vicar, from ASL University, shared his experiences as a deaf person, "[deaf people] tend to congregate around the kitchen table rather than the living room sofa… our good-byes take nearly forever, and our hellos often consist of serious hugs. When two of us meet for the first time we tend to exchange detailed biographies." Deaf culture is not about contemplating what deaf people cannot do and how to fix their problems, an approach known as the "pathological view of the deaf." Instead deaf people celebrate what they can do. There is a strong sense of unity between deaf people as they share their experiences of suffering through a similar struggle. This celebration creates a unity between even deaf strangers. Bill Vicars expresses the power of this bond when stating, "if given the chance to become hearing most [deaf people] would choose to remain deaf."
The United States-based National Association of the Deaf has a statement on its website regarding cochlear implants. The NAD asserts that the choice to implant is up to the individual (or the parents), yet strongly advocates a fully informed decision in all aspects of a cochlear implant. Much of the negative reaction to cochlear implants stems from the medical viewpoint that deafness is a condition that needs to be "cured," while the Deaf community instead regards deafness a defining cultural characteristic.
Many other assistive devices are more acceptable to the Deaf community, including but not limited to, hearing aids, closed captioning, email and the Internet, text telephones, and video relay services.
Sign languages convey meaning through manual communication and body language instead of acoustically conveyed sound patterns. This involves the simultaneous combination of hand shapes, orientation and movement of the hands, arms or body, and facial expressions to express a speaker's thoughts. "Sign languages are based on the idea that vision is the most useful tool a deaf person has to communicate and receive information".
The examples and perspective in this section deal primarily with the United States and do not represent a worldwide view of the subject. (December 2012) (Learn how and when to remove this template message)
Those who are deaf (by either state or federal standards) have access to a free and appropriate public education. If a child does qualify as being deaf or hard of hearing and receives an individualized education plan, the IEP team must consider, "the child's language and communication needs. The IEP must include opportunities for direct communication with peers and professionals. It must also include the student’s academic level, and finally must include the students full range of needs"
In part, the Department of Education defines deafness as "… a hearing impairment that is so severe that the child is impaired in processing linguistic information through hearing, with or without amplification …." Hearing impairment is defined as "… an impairment in hearing, whether permanent or fluctuating, that adversely affects a child's educational performance but that is not included under the definition of deafness …."
Inclusion versus pulloutEdit
The examples and perspective in this article may not represent a worldwide view of the subject. (November 2014) (Learn how and when to remove this template message)
In a residential school where all the children use the same communication system (whether it is a school using ASL, Total Communication or Oralism), students will be able to interact normally with other students, without having to worry about being criticized. An argument supporting inclusion, on the other hand, exposes the student to people who are not just like them, preparing them for adult life. Through interacting, children with hearing disabilities can expose themselves to other cultures which in the future may be beneficial for them when it comes to finding jobs and living on their own in a society where their disability may put them in the minority. These are some reasons why a person may or may not want to put their child in an inclusion classroom.
The communication limitations between people who are deaf and their hearing family members can often cause difficulties in family relationships, and affect the strength of relationships among individual family members. It was found that most people who are deaf have hearing parents, which means that the channel that the child and parents communicate through can be very different, often affecting their relationship in a negative way. If a parent communicates best verbally, and their child communicates best using sign language, this could result in ineffective communication between parents and children. Ineffective communication can potentially lead to fights caused by misunderstanding, less willingness to talk about life events and issues, and an overall weaker relationship. Even if individuals in the family made an effort to learn deaf communication techniques such as sign language, a deaf family member often will feel excluded from casual banter; such as the exchange of daily events and news at the dinner table. It is often difficult for people who are deaf to follow these conversations due to the fast-paced and overlapping nature of these exchanges. This can cause a deaf individual to become frustrated and take part in less family conversations. This can potentially result in weaker relationships between the hearing individual and their immediate family members. This communication barrier can have a particularly negative effect on relationships with extended family members as well. Communication between a deaf individual and their extended family members can be very difficult due to the gap in verbal and non-verbal communication. This can cause the individuals to feel frustrated and unwilling to put effort into communicating effectively. The lack of effort put into communicating can result in anger, miscommunication, and unwillingness to build a strong relationship.
People who have hearing loss can often experience many difficulties as a result of communication barriers among them and other hearing individuals in the community. Some major areas that can be impacted by this are involvement in extracurricular activities and social relationships. For young people, extracurricular activities are vehicles for physical, emotional, social, and intellectual development. However, it is often the case that communication barriers between people who are deaf and their hearing peers and coaches/club advisors limit them from getting involved. These communication barriers make it difficult for someone with a hearing loss to understand directions, take advice, collaborate, and form bonding relationships with other team or club members. As a result, extracurricular activities such as sports teams, clubs, and volunteering are often not as enjoyable and beneficial for individuals who have hearing loss, and they may engage in them less often. A lack of community involvement through extracurricular activities may also limit the individual’s social network. In general, it can be difficult for someone who is deaf to develop and maintain friendships with their hearing peers due to the communication gap that they experience. They can often miss the jokes, informal banter, and "messing around" that is associated with the formation of many friendships among young people. Conversations between people who are deaf and their hearing peers can often be limited and short due to their differences in communication methods and lack of knowledge on how to overcome these differences. Deaf individuals can often experience rejection by hearing peers who are not willing to make an effort to find their way around communication difficulties. Patience and motivation to overcome such communication barriers is required by both the deaf or hard of hearing and hearing individuals in order to establish and maintain good friendships.
Many people tend to forget about the difficulties that deaf children encounter, as they view the deaf child differently from a deaf adult. Deaf children grow up being unable to fully communicate with their parents, siblings and other family members. Examples include being unable to tell their family what they have learned, what they did, asking for help, or even simply being unable to interact in daily conversation. Deaf children have to learn sign language and to read lips at a young age, however they cannot communicate with others using it unless the others are educated in sign language as well. Children who are deaf or hard of hearing are faced with many complications while growing up, for example some children have to wear hearing aids and others require assistance from sign language (ASL) interpreters. The interpreters help them to communicate with other individuals until they develop the skills they need to efficiently communicate on their own. Although growing up for deaf children may entitle more difficulties than for other children, there are many support groups that allow deaf children to interact with other children. This is where they develop friendships. There are also classes for young children to learn sign language in an environment that has other children in their same situation and around their same age. These groups and classes can be very beneficial in providing the child with the proper knowledge and not to mention the societal interactions that they need in order to live a healthy, young, playful and carefree life that any child deserves.
There are three typical adjustment patterns adopted by adults with hearing loss. The first one is to remain withdrawn into your own self. This provides a sense of safety and familiarity which can be a comforting way to lead your life. The second is to act "as if" one does not even have hearing loss. A positive attitude will help people to live a life with no barriers and thus, engage in optimal interaction. The final and third pattern is for the person to accept their hearing loss as a part of them without undervaluing oneself. This means understanding that one is forced to live life with this disability, however it is not the only thing that constitutes life’s meaning. Furthermore, many feel as if their inability to hear others during conversation is their fault. It's important that these individuals learn how to become more assertive individuals who do not lack fear when it comes to asking someone to repeat something or to speak a little louder. Although there is much fatigue and frustration that is produced from one’s inability to hear, it is important to learn from personal experiences in order to improve on one’s communication skills. In essence, these patterns will help adults with hearing loss deal with the communication barriers that are present.
In most instances, people who are deaf find themselves working with hearing colleagues, where they can often be cut off from the communication going on around them. Interpreters can be provided for meetings and workshops, however are seldom provided for everyday work interactions. Communication of important information needed for jobs typically comes in the form of written or verbal summaries, which do not convey subtle meanings such as tone of voice, side conversations during group discussions, and body language. This can result in confusion and misunderstanding for the worker who is deaf, therefore making it harder to do their job effectively. Additionally, deaf workers can be unintentionally left out of professional networks, informal gatherings, and casual conversations among their collogues. Information about informal rules and organizational culture in the workplace is often communicated though these types of interactions, which puts the worker who is deaf at a professional and personal disadvantage. This could sever their job performance due to lack of access to information and therefore, reduce their opportunity to form relationships with their co-workers. Additionally, these communication barriers can all affect a deaf person’s career development. Since being able to effectively communicate with one's co-workers and other people relevant to one's job is essential to managerial positions, people with hearing loss can often be denied such opportunities.
To avoid these situations in the workplace, individuals can take full-time or part-time sign language courses. In this way, they can become better able to communicate with the deaf and hard of hearing. Such courses teach the American Sign Language (ASL) language as most North Americans use this particular language to communicate. It is a visual language made up of specific gestures (signs), hand shapes, and facial expressions that contain their own unique grammatical rules and sentence structures By completing sign language courses, it ensures that deaf individuals feel a part of the workplace and have the ability to communicate with their co-workers and employer in the manner as other hearing employees do.
Not only can communication barriers between deaf and hearing people affect family relationships, work, and school, but they can also have a very significant effect on a deaf individual’s physical and mental health care. As a result of poor communication between the health care professional and the deaf or hard of hearing patient, many patients report that they are not properly informed about their disease and prognosis. This lack of or poor communication could also lead to other issues such as misdiagnosis, poor assessments, mistreatment, and even possibly harm to patients. Poor communication in this setting is often the result of health care providers having the misconception that all people who are deaf or hard of hearing have the same type of hearing loss, and require the same type of communication methods. In reality, there are many different types and range of hearing loss, and in order to communicate effectively a health care provider needs to understand that each individual with hearing loss has unique needs. This affects how individuals have been educated to communicate, as some communication methods work better depending on an individual’s severity of hearing loss. For example, assuming every deaf or hard of hearing patient knows American Sign Language would be incorrect because there are different types of sign language, each varying in signs and meanings. A patient could have been educated to use cued speech which is entirely different from ASL. Therefore, in order to communicate effectively, a health care provider needs to understand that each individual has unique needs when communicating.
Although there are specific laws and rules to govern communication between health care professionals and people who are deaf, they are not always followed due to the health care professional’s insufficient knowledge of communication techniques. This lack of knowledge can lead them to make assumptions about communicating with someone who is deaf, which can in turn cause them to use an unsuitable form of communication. Acts in countries such as the Americans with Disabilities Act (ADA) state that all health care providers are required to provide reasonable communication accommodations when caring for patients who are deaf. These accommodations could include qualified sign language interpreters, CDIs, and technology such as Internet interpretation services. A qualified sign language interpreter will enhance communication between a deaf individual and a health care professional by interpreting not only a health professional’s verbal communication, but also their non-verbal such as expressions, perceptions, and body language. A Certified Deaf Interpreter (CDI) is a sign language interpreter who is also a member of the Deaf community. They accompany a sign language interpreter and are useful for communication with deaf individuals who also have language or cognitive deficits. A CDI will transform what the health care professional communicates into basic, simple language. This method takes much longer, however it can also be more effective than other techniques. Internet interpretation services are convenient and less costly, but can potentially pose significant risks. They involve the use of a sign language interpreter over a video device rather than directly in the room. This can often be an inaccurate form of communication because the interpreter may not be licensed, is often unfamiliar with the patient and their signs, and can lack knowledge of medical terminology.
Aside from utilizing interpreters, healthcare professionals can improve their communication with deaf or hard of hearing patients by educating themselves on common misconceptions and proper practices depending on the patient’s needs. For example, a common misconception is that exaggerating words and speaking loudly will help the patient understand more clearly. However, many individuals with hearing loss depend on lip-reading to identify words. Exaggerated pronunciation and a raised voice can distort the lips, making it even more difficult to understand. Another common mistake health care professionals make are the use of single words rather than full sentences. Although language should be kept simple and short, keeping context is important because certain homophonous words are difficult to distinguish by lip-reading. Health care professionals can further improve their own communication with their patients by eliminating any background noise and positioning themselves in a way where their face is clearly visible to the patient, and suitably lit. The healthcare professional should know how to use body language and facial expressions to properly communicate different feelings.
Stem cell transplant and gene therapyEdit
A 2005 study achieved successful regrowth of cochlea cells in guinea pigs. However, the regrowth of cochlear hair cells does not imply the restoration of hearing sensitivity, as the sensory cells may or may not make connections with neurons that carry the signals from hair cells to the brain. A 2008 study has shown that gene therapy targeting Atoh1 can cause hair cell growth and attract neuronal processes in embryonic mice. Some hope that a similar treatment will one day ameliorate hearing loss in humans.
Recent research, reported in 2012 achieved growth of cochlear nerve cells resulting in hearing improvements in gerbils, using stem cells. Also reported in 2013 was regrowth of hair cells in deaf adult mice using a drug intervention resulting in hearing improvement. The Hearing Health Foundation in the US has embarked on a project called the Hearing Restoration Project. Also Action on Hearing Loss in the UK is also aiming to restore hearing.
Researchers reported in 2015 that genetically deaf mice which were treated with TMC1 gene therapy recovered some of their hearing. In 2017, additional studies were performed to treat Usher syndrome and here, a recombinant adeno-associated virus seemed to outperform the older vectors.
Besides research studies seeking to improve hearing, such as the ones listed above, research studies on the deaf have also been carried out in order to understand more about audition. Pijil and Shwarz (2005) conducted their study on the deaf who lost their hearing later in life and, hence, used cochlear implants to hear. They discovered further evidence for rate coding of pitch, a system that codes for information for frequencies by the rate that neurons fire in the auditory system, especially for lower frequencies as they are coded by the frequencies that neurons fire from the basilar membrane in a synchronous manner. Their results showed that the subjects could identify different pitches that were proportional to the frequency stimulated by a single electrode. The lower frequencies were detected when the basilar membrane was stimulated, providing even further evidence for rate coding.
- Elsevier, Dorland's Illustrated Medical Dictionary, Elsevier.
- "Deafness and hearing loss Fact sheet N°300". March 2015. Archived from the original on 16 May 2015. Retrieved 23 May 2015.
- Shearer AE, Hildebrand MS, Smith RJ (2014). "Deafness and Hereditary Hearing Loss Overview". In Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJ, Stephens K, Amemiya A (eds.). GeneReviews [Internet]. Seattle (WA): University of Washington, Seattle. PMID 20301607.
- Global Burden of Disease Study 2013 Collaborators (October 2016). "Global, regional, and national incidence, prevalence, and years lived with disability for 310 diseases and injuries, 1990-2015: a systematic analysis for the Global Burden of Disease Study 2015". Lancet. 388 (10053): 1545–1602. doi:10.1016/S0140-6736(16)31678-6. PMC 5055577. PMID 27733282.
- "Deafness". Encyclopædia Britannica Online. Encyclopædia Britannica Inc. 2011. Archived from the original on 2012-06-25. Retrieved 2012-02-22.
- Lasak JM, Allen P, McVay T, Lewis D (March 2014). "Hearing loss: diagnosis and management". Primary Care. 41 (1): 19–31. doi:10.1016/j.pop.2013.10.003. PMID 24439878.
- Fowler, Karen B. (2013-12-15). "Congenital Cytomegalovirus Infection: Audiologic Outcome". Clinical Infectious Diseases. 57 (suppl_4): S182–S184. doi:10.1093/cid/cit609. ISSN 1537-6591. PMC 3836573. PMID 24257423.
- "1.1 billion people at risk of hearing loss WHO highlights serious threat posed by exposure to recreational noise" (PDF). who.int. 27 February 2015. Archived (PDF) from the original on 1 May 2015. Retrieved 2 March 2015.
- Global Burden of Disease Study 2013 Collaborators (August 2015). "Global, regional, and national incidence, prevalence, and years lived with disability for 301 acute and chronic diseases and injuries in 188 countries, 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013". Lancet. 386 (9995): 743–800. doi:10.1016/s0140-6736(15)60692-4. PMC 4561509. PMID 26063472.
- WHO (2008). The global burden of disease: 2004 update (PDF). Geneva, Switzerland: World Health Organization. p. 35. ISBN 9789241563710. Archived (PDF) from the original on 2013-06-24.
- Olusanya BO, Neumann KJ, Saunders JE (May 2014). "The global burden of disabling hearing impairment: a call to action". Bulletin of the World Health Organization. 92 (5): 367–73. doi:10.2471/blt.13.128728. PMC 4007124. PMID 24839326.
- Elzouki AY (2012). Textbook of clinical pediatrics (2 ed.). Berlin: Springer. p. 602. ISBN 9783642022012. Archived from the original on 2015-12-14.
- "Community and Culture - Frequently Asked Questions". nad.org. National Association of the Deaf. Archived from the original on 27 December 2015. Retrieved 31 July 2014.
- "Sound and Fury - Cochlear Implants - Essay". www.pbs.org. PBS. Archived from the original on 2015-07-06. Retrieved 2015-08-01.
- "Understanding Deafness: Not Everyone Wants to Be 'Fixed'". www.theatlantic.com. The Atlantic. 2013-08-09. Archived from the original on 2015-07-30. Retrieved 2015-08-01.
- Williams S (2012-09-13). "Why not all deaf people want to be cured". www.telegraph.co.uk. The Daily Telegraph. Archived from the original on 2015-09-24. Retrieved 2015-08-02.
- Sparrow R (2005). "Defending Deaf Culture: The Case of Cochlear Implants" (PDF). The Journal of Political Philosophy. 13 (2). Retrieved 30 November 2014.
- eBook: Current Diagnosis & Treatment in Otolaryngology: Head & Neck Surgery, Lalwani, Anil K. (Ed.) Chapter 44: Audiologic Testing by Brady M. Klaves, PhD, Jennifer McKee Bold, AuD, Access Medicine
- "Community and Culture - Frequently Asked Questions". nad.org. National Association of the Deaf. Archived from the original on 2015-12-27. Retrieved 27 Jan 2016.
- ANSI 7029:2000/BS 6951 Acoustics - Statistical distribution of hearing thresholds as a function of age
- ANSI S3.5-1997 Speech Intelligibility Index (SII)
- Robinson DW, Sutton GJ (1979). "Age effect in hearing - a comparative analysis of published threshold data". Audiology. 18 (4): 320–34. doi:10.3109/00206097909072634. PMID 475664.
- Worrall, L.,& Hickson, L. M. (2003). "Communication activity limitations", pp. 141–142 in Linda E. Worrall & Louise M. Hickson (Eds.). Communication disability in aging: from prevention to intervention. Clifton Park, NY: Delmar Learning
- "Hearing Loss and Older Adults" (Last Updated June 3, 2016). National Institute on Deafness and Other Communication Disorders. 2016-01-26. Archived from the original on October 4, 2016. Retrieved September 11, 2016.
- Oishi N, Schacht J (June 2011). "Emerging treatments for noise-induced hearing loss". Expert Opinion on Emerging Drugs. 16 (2): 235–45. doi:10.1517/14728214.2011.552427. PMC 3102156. PMID 21247358.
- "CDC - NIOSH Science Blog – A Story of Impact…". cdc.gov. Archived from the original on 2015-06-13.
- "Noise and Hearing Conservation: Effects of Excessive Exposure". Occupational Safety & Health Administration. Archived from the original on June 29, 2016. Retrieved July 14, 2016.
- "Threshold Shift (TS)". Simon Fraser University. Archived from the original on 2016-05-03. Retrieved 2016-07-14.
- "About Hearing Loss". Centers for Disease Control and Prevention. Archived from the original on 2016-07-20. Retrieved 2016-07-15.
- In the United States, United States Environmental Protection Agency, Occupational Safety and Health Administration, National Institute for Occupational Safety and Health, Mine Safety and Health Administration, and numerous state government agencies among others, set noise standards.
- Information on Levels of Environmental Noise Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety. Document ID: usepa-1974
- "Deafness". SANDRA: South African National Deaf Association. Archived from the original on 2016-08-01. Retrieved 2016-07-14.
- Occupational Noise Exposure, National Institute for Occupational Safety and Health 98-126
- "Compliance Guide to MSHA's Occupational Noise Exposure Standard, APPENDIX B – GLOSSARY OF TERMS". Archived from the original on 2013-11-12.
- "Noise-Induced Hearing Loss: Promoting Hearing Health Among Youth". CDC Healthy Youth!. CDC. 2009-07-01. Archived from the original on 2009-12-21.
- Goines L, Hagler L (March 2007). "Noise Pollution: A Modern Plague". Southern Medical Journal. 100 (3): 287–294. CiteSeerX 10.1.1.504.8717. doi:10.1097/smj.0b013e3180318be5.
- Rosen S, Bergman M, Plester D, El-Mofty A, Satti MH (September 1962). "Presbycusis study of a relatively noise-free population in the Sudan". The Annals of Otology, Rhinology, and Laryngology. 71 (3): 727–43. doi:10.1177/000348946207100313. PMID 13974856.
- Bergman M (October 1966). "Hearing in the Mabaans. A critical review of related literature". Archives of Otolaryngology. 84 (4): 411–5. doi:10.1001/archotol.1966.00760030413007. PMID 5921716.
- Goycoolea MV, Goycoolea HG, Farfan CR, Rodriguez LG, Martinez GC, Vidal R (December 1986). "Effect of life in industrialized societies on hearing in natives of Easter Island". The Laryngoscope. 96 (12): 1391–6. doi:10.1288/00005537-198612000-00015. PMID 3784745.
- Committee on Noise-Induced Hearing Loss and Tinnitus Associated with Military Service from World War II to the Present, Medical Follow-up Agency (2006). Humes L, Joellenbeck L, Durch J (eds.). Noise and military service : implications for hearing loss and tinnitus (PDF). 500 Fifth Street, N.W., Washington, DC 20001: THE NATIONAL ACADEMIES PRESS. pp. 72–111. ISBN 978-0-309-09949-3. Archived from the original (eBook) on 24 December 2014. Retrieved 26 November 2014.
- de Laat JA, van Deelen L, Wiefferink K (September 2016). "Hearing Screening and Prevention of Hearing Loss in Adolescents". The Journal of Adolescent Health. 59 (3): 243–245. doi:10.1016/j.jadohealth.2016.06.017. PMID 27562364.
- Murphy WJ, Eichwald J, Meinke DK, Chadha S, Iskander J (March 2018). "CDC Grand Rounds: Promoting Hearing Health Across the Lifespan". MMWR. Morbidity and Mortality Weekly Report. 67 (8): 243–246. doi:10.15585/mmwr.mm6708a2. PMC 5861697. PMID 29494567.
- Rehm H. "The Genetics of Deafness; A Guide for Patients and Families" (PDF). Harvard Medical School Center For Hereditary Deafness. Harvard Medical School. Archived from the original (PDF) on 2013-10-19.
- Lynch ED, Lee MK, Morrow JE, Welcsh PL, León PE, King MC (November 1997). "Nonsyndromic deafness DFNA1 associated with mutation of a human homolog of the Drosophila gene diaphanous". Science. 278 (5341): 1315–8. doi:10.1126/science.278.5341.1315. PMID 9360932.
- Starr A, Sininger YS, Pratt H (2011). "The varieties of auditory neuropathy". Journal of Basic and Clinical Physiology and Pharmacology. 11 (3): 215–30. doi:10.1515/JBCPP.2000.11.3.215. PMID 11041385.
- Starr A, Picton TW, Sininger Y, Hood LJ, Berlin CI (June 1996). "Auditory neuropathy". Brain. 119 ( Pt 3) (3): 741–53. doi:10.1093/brain/119.3.741. PMID 8673487.
- Rodman R, Pine HS (June 2012). "The otolaryngologist's approach to the patient with Down syndrome". Otolaryngologic Clinics of North America. 45 (3): 599–629, vii–viii. doi:10.1016/j.otc.2012.03.010. PMID 22588039.
- McKusick VA, Kniffen CL (30 January 2012). "# 118300 CHARCOT-MARIE-TOOTH DISEASE AND DEAFNESS". Online Mendelian Inheritance in Man. Retrieved 2 March 2018.
- Byl FM, Adour KK (March 1977). "Auditory symptoms associated with herpes zoster or idiopathic facial paralysis". The Laryngoscope. 87 (3): 372–9. doi:10.1288/00005537-197703000-00010. PMID 557156.
- Araújo E, Zucki F, Corteletti LC, Lopes AC, Feniman MR, Alvarenga K (2012). "Hearing loss and acquired immune deficiency syndrome: systematic review". Jornal Da Sociedade Brasileira De Fonoaudiologia. 24 (2): 188–92. doi:10.1590/s2179-64912012000200017. PMID 22832689.
- Curhan SG, Shargorodsky J, Eavey R, Curhan GC (September 2012). "Analgesic use and the risk of hearing loss in women". American Journal of Epidemiology. 176 (6): 544–54. doi:10.1093/aje/kws146. PMC 3530351. PMID 22933387. Archived from the original on 2015-12-14.
- Cone B, Dorn P, Konrad-Martin D, Lister J, Ortiz C, Schairer K. "Ototoxic Medications (Medication Effects)". American Speech-Language-Hearing Association.
- Rybak LP, Mukherjea D, Jajoo S, Ramkumar V (November 2009). "Cisplatin ototoxicity and protection: clinical and experimental studies". The Tohoku Journal of Experimental Medicine. 219 (3): 177–86. doi:10.1620/tjem.219.177. PMC 2927105. PMID 19851045.
- Rybak LP, Ramkumar V (October 2007). "Ototoxicity". Kidney International. 72 (8): 931–5. doi:10.1038/sj.ki.5002434. PMID 17653135.
- "FDA Announces Revisions to Labels for Cialis, Levitra and Viagra". Food and Drug Administration. 2007-10-18. Archived from the original on 2011-10-23. Retrieved 2011-10-30.
- Yorgason JG, Fayad JN, Kalinec F (May 2006). "Understanding drug ototoxicity: molecular insights for prevention and clinical management". Expert Opinion on Drug Safety. 5 (3): 383–99. doi:10.1517/14740322.214.171.1243. PMID 16610968.
- Kranzer K, Elamin WF, Cox H, Seddon JA, Ford N, Drobniewski F (November 2015). "A systematic review and meta-analysis of the efficacy and safety of N-acetylcysteine in preventing aminoglycoside-induced ototoxicity: implications for the treatment of multidrug-resistant TB". Thorax. 70 (11): 1070–7. doi:10.1136/thoraxjnl-2015-207245. PMID 26347391.
- "Tox Town – Toluene – Toxic chemicals and environmental health risks where you live and work – Text Version". toxtown.nlm.nih.gov. Archived from the original on 2010-06-09. Retrieved 2010-06-09.
- Morata TC. "Addressing the Risk for Hearing Loss from Industrial Chemicals". CDC. Archived from the original on 2009-01-22. Retrieved 2008-06-05.
- Johnson A (2008-09-09). "Occupational exposure to chemicals and hearing impairment – the need for a noise notation" (PDF). Karolinska Institutet: 1–48. Archived from the original (PDF) on 2012-09-06. Retrieved 2009-06-19.
- Venet T, Campo P, Thomas A, Cour C, Rieger B, Cosnier F (March 2015). "The tonotopicity of styrene-induced hearing loss depends on the associated noise spectrum". Neurotoxicology and Teratology. 48: 56–63. doi:10.1016/j.ntt.2015.02.003. PMID 25689156.
- Fuente A, Qiu W, Zhang M, Xie H, Kardous CA, Campo P, Morata TC (March 2018). "Use of the kurtosis statistic in an evaluation of the effects of noise and solvent exposures on the hearing thresholds of workers: An exploratory study". The Journal of the Acoustical Society of America. 143 (3): 1704. doi:10.1121/1.5028368. PMID 29604694.
- Sliwinska-Kowalska M, Zamyslowska-Szmytke E, Szymczak W, Kotylo P, Fiszer M, Wesolowski W, Pawlaczyk-Luszczynska M (May 2005). "Exacerbation of noise-induced hearing loss by co-exposure to workplace chemicals". Environmental Toxicology and Pharmacology. 19 (3): 547–53. doi:10.1016/j.etap.2004.12.018. PMID 21783525.
- "Preventing Hearing Loss Caused by Chemical (Ototoxicity) and Noise Exposure" (PDF). Retrieved 4 April 2018.
- Oesterle EC (March 2013). "Changes in the adult vertebrate auditory sensory epithelium after trauma". Hearing Research. 297: 91–8. doi:10.1016/j.heares.2012.11.010. PMC 3637947. PMID 23178236.
- Eggermont JJ (January 2017). "Acquired hearing loss and brain plasticity". Hearing Research. 343: 176–190. doi:10.1016/j.heares.2016.05.008. PMID 27233916.
- "How We Hear". American Speech-Language-Hearing Association. Retrieved 2 March 2018.
- "How We Hear". Archived from the original on 1 May 2017.
- "How Do We Hear?". NIDCD. January 3, 2018.
- "What Is Noise-Induced Hearing Loss?". NIH - Noisy Planet. December 27, 2017.
- "CDC - Noise and Hearing Loss Prevention - Preventing Hearing Loss, Risk Factors - NIOSH Workplace Safety and Health Topic". NIOSH/CDC. 5 February 2018. Retrieved 3 March 2018.
- "Age-Related Hearing Loss". NIDCD. 18 August 2015.
- Jansen S, Luts H, Dejonckere P, van Wieringen A, Wouters J (2013). "Efficient hearing screening in noise-exposed listeners using the digit triplet test" (PDF). Ear and Hearing. 34 (6): 773–8. doi:10.1097/AUD.0b013e318297920b. PMID 23782715.
- "BIAP Recommendation 02/1 bis - AUDIOMETRIC CLASSIFICATION OF HEARING IMPAIRMENTS". biap.org. International Bureau Audiophonology. 26 October 1996. Archived from the original on 8 September 2017. Retrieved 18 June 2017.
- Russell JL, Pine HS, Young DL (August 2013). "Pediatric cochlear implantation: expanding applications and outcomes". Pediatric Clinics of North America. 60 (4): 841–63. doi:10.1016/j.pcl.2013.04.008. PMID 23905823.
- Lieu JE (May 2004). "Speech-language and educational consequences of unilateral hearing loss in children". Archives of Otolaryngology–Head & Neck Surgery. 130 (5): 524–30. doi:10.1001/archotol.130.5.524. PMID 15148171.
- Kitterick PT, O'Donoghue GM, Edmondson-Jones M, Marshall A, Jeffs E, Craddock L, Riley A, Green K, O'Driscoll M, Jiang D, Nunn T, Saeed S, Aleksy W, Seeber BU (Aug 11, 2014). "Comparison of the benefits of cochlear implantation versus contra-lateral routing of signal hearing aids in adult patients with single-sided deafness: study protocol for a prospective within-subject longitudinal trial". BMC Ear, Nose, and Throat Disorders. 14 (1): 7. doi:10.1186/1472-6815-14-7. PMC 4141989. PMID 25152694.
- Riss D, Arnoldner C, Baumgartner WD, Blineder M, Flak S, Bachner A, Gstoettner W, Hamzavi JS (December 2014). "Indication criteria and outcomes with the Bonebridge transcutaneous bone-conduction implant". The Laryngoscope. 124 (12): 2802–6. doi:10.1002/lary.24832. PMID 25142577.
- Graham eb, Baguley DM (2009). Ballantyne's Deafness (7th ed.). Chichester: John Wiley & Sons. p. 16. ISBN 978-0-470-74441-3. Archived from the original on 2017-09-08.CS1 maint: Extra text: authors list (link)
- "Childhood hearing loss: act now, here's how!" (PDF). WHO. 2016. p. 6. Archived (PDF) from the original on 6 March 2016. Retrieved 2 March 2016.
Over 30% of childhood hearing loss is caused by diseases such as measles, mumps, rubella, meningitis and ear infections. These can be prevented through immunization and good hygiene practices. Another 17% of childhood hearing loss results from complications at birth, including prematurity, low birth weight, birth asphyxia and neonatal jaundice. Improved maternal and child health practices would help to prevent these complications. The use of ototoxic medicines in expectant mothers and newborns, which is responsible for 4% of childhood hearing loss, could potentially be avoided.
- Davis A, McMahon CM, Pichora-Fuller KM, Russ S, Lin F, Olusanya BO, Chadha S, Tremblay KL (April 2016). "Aging and Hearing Health: The Life-course Approach". The Gerontologist. 56 Suppl 2 (Suppl_2): S256–67. doi:10.1093/geront/gnw033. PMID 26994265. Archived from the original on 2017-03-18.
- El Dib RP, Mathew JL, Martins RH (April 2012). El Dib RP (ed.). "Interventions to promote the wearing of hearing protection". The Cochrane Database of Systematic Reviews. 4 (4): CD005234. doi:10.1002/14651858.CD005234.pub5. PMID 22513929. (Retracted, see doi:10.1002/14651858.cd005234.pub6. If this is an intentional citation to a retracted paper, please replace
- Stucken EZ, Hong RS (October 2014). "Noise-induced hearing loss: an occupational medicine perspective". Current Opinion in Otolaryngology & Head and Neck Surgery. 22 (5): 388–93. doi:10.1097/moo.0000000000000079. PMID 25188429.
- "Noise and Hearing Loss Prevention". Centers for Disease Control and Prevention: National Institute for Occupational Safety and Health. Archived from the original on July 9, 2016. Retrieved July 15, 2016.
- "Safety and Health Topics: Occupational Noise Exposure". Occupational Safety and Health Administration. Archived from the original on May 6, 2016. Retrieved July 15, 2015.
- "Controls for Noise Exposure". Centers for Disease Control and Prevention: National Institute for Occupational Safety and Health. Archived from the original on July 4, 2016. Retrieved July 15, 2016.
- "Excellence in Hearing Loss Prevention Award". Safe-in-Sound. Archived from the original on May 27, 2016. Retrieved July 15, 2016.
- "Buy Quiet". Centers for Disease Control and Prevention: National Institute for Occupational Safety and Health. Archived from the original on August 8, 2016. Retrieved July 15, 2016.
- "PowerTools Database". Centers for Disease Control and Prevention: National Institute for Occupational Safety and Health. Archived from the original on June 30, 2016. Retrieved July 15, 2016.
- "CDC - NIOSH Publications and Products - Occupationally-Induced Hearing Loss (2010-136)". cdc.gov. 2010. doi:10.26616/NIOSHPUB2010136. Archived from the original on 2016-05-12.
- Tikka C, Verbeek JH, Kateman E, Morata TC, Dreschler WA, Ferrite S (July 2017). "Interventions to prevent occupational noise-induced hearing loss". The Cochrane Database of Systematic Reviews. 7: CD006396. doi:10.1002/14651858.cd006396.pub4. PMID 28685503.
- Moyer VA (2012-11-06). "Screening for Hearing Loss in Older Adults: U.S. Preventive Services Task Force Recommendation Statement". Annals of Internal Medicine. The American College of Physicians. pp. 655–661. Archived from the original on 2012-10-27. Retrieved 2012-11-06.
- "Who Should be Screened for Hearing Loss". www.asha.org. Retrieved 2017-03-17.
- "Hearing and Other Sensory or Communication Disorders | Healthy People 2020". www.healthypeople.gov. Archived from the original on 2017-03-18. Retrieved 2017-03-17.
- World Health Organization, WHO (2017). Global costs of unaddressed hearing loss and cost-effectiveness of interventions: a WHO report. Geneva: World Health Organization. pp. 5–10. ISBN 978-92-4-151204-6.
- Hoffman HJ, Dobie RA, Losonczy KG, Themann CL, Flamme GA (March 2017). "Declining Prevalence of Hearing Loss in US Adults Aged 20 to 69 Years". JAMA Otolaryngology–Head & Neck Surgery. 143 (3): 274–285. doi:10.1001/jamaoto.2016.3527. PMC 5576493. PMID 27978564.
- Carroll YI, Eichwald J, Scinicariello F, Hoffman HJ, Deitchman S, Radke MS, Themann CL, Breysse P (February 2017). "Vital Signs: Noise-Induced Hearing Loss Among Adults - United States 2011-2012". MMWR. Morbidity and Mortality Weekly Report. 66 (5): 139–144. doi:10.15585/mmwr.mm6605e3. PMC 5657963. PMID 28182600. Archived from the original on 2017-02-25.
- Frishberg N (September 1975). "Arbitrariness and Iconicity: Historical Change in American Sign Language". Language. 51 (3): 696–719. doi:10.2307/412894. JSTOR 412894.
- Meyer C, Scarinci N, Ryan B, Hickson L (December 2015). ""This Is a Partnership Between All of Us": Audiologists' Perceptions of Family Member Involvement in Hearing Rehabilitation". American Journal of Audiology. 24 (4): 536–48. doi:10.1044/2015_AJA-15-0026. PMID 26649683.
- Niparko JK, Tobey EA, Thal DJ, Eisenberg LS, Wang NY, Quittner AL, Fink NE (April 2010). "Spoken language development in children following cochlear implantation". JAMA. 303 (15): 1498–506. doi:10.1001/jama.2010.451. PMC 3073449. PMID 20407059.
- Kral A, O'Donoghue GM (October 2010). "Profound deafness in childhood". The New England Journal of Medicine. 363 (15): 1438–50. doi:10.1056/NEJMra0911225. PMID 20925546.
- Hall WC (May 2017). "What You Don't Know Can Hurt You: The Risk of Language Deprivation by Impairing Sign Language Development in Deaf Children". Maternal and Child Health Journal. 21 (5): 961–965. doi:10.1007/s10995-017-2287-y. PMC 5392137. PMID 28185206.
- Mayberry R (2007). "When timing is everything: Age of first-language acquisition effects on second-language learning". Applied Psycholinguistics. 28 (3): 537–549. doi:10.1017/s0142716407070294.
- Deaf Heritage: A Narrative History of Deaf America by Jack Gannon (National Association of the Deaf, 1981)
- "American Deaf Culture". Sign Media, Incorporated. Sign Media, Inc. Archived from the original on 22 May 2013. Retrieved 14 May 2013.
- Drolsbaugh M. "Everything You've Wanted to Know About Deaf Culture (And Then Some)". Deaf Culture Online. Archived from the original on 2011-02-13. Retrieved 2011-11-28.
- NAD Cochlear Implant Committee. "NAD Position Statement on Cochlear Implants (2000)". Cochlear Implants %7c National Association of the Deaf. National Association of the Deaf. Archived from the original on 5 December 2014. Retrieved 30 November 2014.
- "American Sign Language". NIDCD. 2015-08-18. Archived from the original on 15 November 2016. Retrieved 17 November 2016.
- "Deaf Students Education Services". Archived from the original on 2016-01-16. Retrieved 2016-01-29.
- Smith DD, Tyler NC (2010). "Introduction to Special Education". Columbus: Merrill.
- "Regulations: Part 300 / A / 300.8 / c". U. S. Department of Education. U. S. Department of Education. Archived from the original on 15 July 2015. Retrieved 9 August 2015.
- Foster S (1996). "Communication experiences of deaf people: An ethnographic account.". In Parasnis I (ed.). Cultural and language diversity of the deaf experience. New York: Cambridge University Press. pp. 117–136.
- Scherer MJ (2004). "The Personal Meaning of Hearing or Vision Loss.". Connecting To Learn Educational and Assistive Technology for People With Disabilities. Washington, DC: American Psychological Association. pp. 41–55.
- Sign Language Classes for Individuals. (2013, January 1). Retrieved November 5, 2014.
- Medicina Oral, Patología Oral y Cirugía Bucal. (2007, January 1). Retrieved October 31, 2014, from Alsmark SS, García J, Martínez MR, López NE (December 2007). "How to improve communication with deaf children in the dental clinic". Medicina Oral, Patologia Oral Y Cirugia Bucal. 12 (8): E576–81. PMID 18059242. Archived from the original on 2014-11-05. Retrieved 2014-11-05.
- Ramstead, A. (2014, January 15). The Role of the Certified Deaf Interpreter. Retrieved November 2, 2014, from "The Role of the Deaf Interpreter". Archived from the original on 2014-11-05. Retrieved 2014-11-05.
- Schuler, G., Mistler, L., Torrey, K., & Depukat, R. (2013). Bridging Communication Gaps with the Deaf. Nursing, 43(11), 24-30.
- Coghlan A (2005-02-14). "Gene therapy is first deafness 'cure'". NewScientist.com News Service. Archived from the original on 2008-09-14.
- Gubbels SP, Woessner DW, Mitchell JC, Ricci AJ, Brigande JV (September 2008). "Functional auditory hair cells produced in the mammalian cochlea by in utero gene transfer". Nature. 455 (7212): 537–41. doi:10.1038/nature07265. PMC 2925035. PMID 18754012.
- Gewin V (2012-09-12). "Human embryonic stem cells restore gerbil hearing". Nature News. doi:10.1038/nature.2012.11402. Archived from the original on 2012-12-14. Retrieved 2013-01-22.
- Ander D. "Drug may reverse permanent deafness by regenerating cells of inner ear: Harvard study". National Post. National Post. Archived from the original on 2013-02-16.
- "Hearing Health Foundation". HHF. Archived from the original on 2013-01-27. Retrieved 2013-01-22.
- "Biomedical research – Action On Hearing Loss". RNID. Retrieved 2013-01-22.
- Gallacher J (9 July 2015). "Deafness could be treated by virus, say scientists". UK: BBC. Archived from the original on 9 July 2015. Retrieved 9 July 2015.
- Askew C, Rochat C, Pan B, Asai Y, Ahmed H, Child E, Schneider BL, Aebischer P, Holt JR (July 2015). "Tmc gene therapy restores auditory function in deaf mice". Science Translational Medicine. 7 (295): 295ra108. doi:10.1126/scitranslmed.aab1996. PMID 26157030.
- Isgrig K, Shteamer JW, Belyantseva IA, Drummond MC, Fitzgerald TS, Vijayakumar S, Jones SM, Griffith AJ, Friedman TB, Cunningham LL, Chien WW (March 2017). "Gene Therapy Restores Balance and Auditory Functions in a Mouse Model of Usher Syndrome". Molecular Therapy. 25 (3): 780–791. doi:10.1016/j.ymthe.2017.01.007. PMC 5363211. PMID 28254438.
- Landegger LD, Pan B, Askew C, Wassmer SJ, Gluck SD, Galvin A, Taylor R, Forge A, Stankovic KM, Holt JR, Vandenberghe LH (March 2017). "A synthetic AAV vector enables safe and efficient gene transfer to the mammalian inner ear". Nature Biotechnology. 35 (3): 280–284. doi:10.1038/nbt.3781. PMC 5340646. PMID 28165475.
- Pan B, Askew C, Galvin A, Heman-Ackah S, Asai Y, Indzhykulian AA, Jodelka FM, Hastings ML, Lentz JJ, Vandenberghe LH, Holt JR, Géléoc GS (March 2017). "Gene therapy restores auditory and vestibular function in a mouse model of Usher syndrome type 1c". Nature Biotechnology. 35 (3): 264–272. doi:10.1038/nbt.3801. PMC 5340578. PMID 28165476.
- Carlson NR (2010). Physiology of behavior (11th ed.). Upper Saddle River, New Jersey: Pearson Education, Inc.
|Wikimedia Commons has media related to Hearing impairment.|
|Wikiquote has quotations related to: Hearing loss|
- Hearing loss at Curlie
- National Institute for the Prevention of Deafness and other Communication Disorders
- World Health Organization Global Costs of unaddressed hearing loss and cost-effectiveness of interventions, 2017 
- "Hearing Loss in Children". Hearing Loss in Children Home. Retrieved 17 March 2017.
- Occupational Noise and Hearing Loss Prevention (NIOSH)
- OSHA-NIOSH 2018. Preventing Hearing Loss Caused by Chemical (Ototoxicity) and Noise Exposure Safety and Health Information Bulletin (SHIB), Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health. SHIB 03-08-2018. DHHS (NIOSH) Publication No. 2018-124.
- Centers for Disease Control and Prevention Vital Signs- Hearing Loss