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Hearing, or auditory perception, is the ability to perceive
sounds In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the br ...

sounds
through an organ, such as an
ear The ear is the organ of hearing and, in mammals, balance. In mammals, the ear is usually described as having three parts—the outer ear The outer ear, external ear, or auris externa is the external part of the ear, which consists ...

ear
, by detecting
vibrations Vibration is a mechanical phenomenon whereby oscillation Oscillation is the repetitive variation, typically in time Time is the indefinite continued sequence, progress of existence and event (philosophy), events that occur in an apparentl ...

vibrations
as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is
auditory science Auditory science or hearing science is a field of research and education concerning the perception of sounds by humans, animals, or machines. It is a heavily interdisciplinary field at the crossroad between acoustics Acoustics is a branch of phys ...
. Sound may be heard through
solid Solid is one of the four fundamental states of matter (the others being liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied ...

solid
,
liquid A liquid is a nearly incompressible In fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics Mechanics (Ancient Greek, Greek: ) is the area of physics concerned with the motions of physical objects, ...

liquid
, or
gas Gas is one of the four fundamental states of matter In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space ...

gas
eous matter. It is one of the traditional five
sense A sense is a biological system A biological system is a complex biological network, network which connects several biologically relevant entities. Biological organization spans several scales and are determined based different structures dependi ...

sense
s. Partial or total inability to hear is called
hearing loss Hearing loss is a partial or total inability to hear Hearing, or auditory perception, is the ability to perceive Sound, sounds by detecting Vibration, vibrations, changes in the pressure of the surrounding medium through time, through a ...
. In humans and other vertebrates, hearing is performed primarily by the
auditory system The auditory system is the sensory system The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons (including the sensory receptor cells), neur ...
:
mechanical wave A mechanical wave is a wave In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics) ...
s, known as vibrations, are detected by the
ear The ear is the organ of hearing and, in mammals, balance. In mammals, the ear is usually described as having three parts—the outer ear The outer ear, external ear, or auris externa is the external part of the ear, which consists ...

ear
and transduced into nerve impulses that are perceived by the
brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tiss ...

brain
(primarily in the
temporal lobe The temporal lobe is one of the four major lobes of the cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex m ...

temporal lobe
). Like
touch The somatosensory system is a part of the sensory nervous system The sensory nervous system is a part of the nervous system responsible for processing sense, sensory information. A sensory system consists of sensory neurons (including the sen ...

touch
, audition requires sensitivity to the movement of molecules in the world outside the organism. Both hearing and touch are types of
mechanosensationMechanosensation is the transduction of mechanical stimuli into neural signals. Mechanosensation provides the basis for the sense A sense is a biological system used by an organism for sensation, the process of gathering information about the wor ...
.


Hearing mechanism

There are three main components of the human
auditory system The auditory system is the sensory system The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons (including the sensory receptor cells), neur ...
: the outer ear, the middle ear, and the inner ear.


Outer ear

The outer ear includes the pinna, the visible part of the ear, as well as the
ear canal The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear The outer ear, external ear, or auris externa is the external part of the ear, which consists of the auricle (anatomy), auricle ...
, which terminates at the
eardrum In the anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is a ...
, also called the tympanic membrane. The pinna serves to focus sound waves through the ear canal toward the eardrum. Because of the asymmetrical character of the outer ear of most mammals, sound is filtered differently on its way into the ear depending on the location of its origin. This gives these animals the ability to localize sound vertically. The eardrum is an airtight membrane, and when sound waves arrive there, they cause it to vibrate following the
waveform In electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons The electron is a subatomic particle In physical sciences, subatomic part ...
of the sound.
Cerumen Earwax, also known by the medical term cerumen, is a brown, orange, red, yellowish or gray waxy substance secreted in the ear canal of humans and other mammals. It protects the skin of the human ear canal, assists in cleaning and lubrication, ...

Cerumen
(ear wax) is produced by
ceruminousCeruminous glands are specialized sudoriferous glands (sweat glands) located subcutaneously in the external auditory canal, in the outer 1/3. Ceruminous glands are simple, coiled, tubular glands made up of an inner secretory layer of cells and an out ...
and
sebaceous gland A sebaceous gland is a microscopic exocrine Exocrine glands are gland In animals, a gland is a group of cells in an animal's body that synthesizes substances (such as hormone A hormone (from the Greek participle , "setting in motion") is a ...
s in the skin of the human ear canal, protecting the ear canal and tympanic membrane from physical damage and microbial invasion.


Middle ear

The middle ear consists of a small air-filled chamber that is located medial to the eardrum. Within this chamber are the three smallest bones in the body, known collectively as the
ossicles The ossicles (also called auditory ossicles) are three bone A bone is a rigid tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a spe ...
which include the malleus, incus, and stapes (also known as the hammer, anvil, and stirrup, respectively). They aid in the transmission of the vibrations from the eardrum into the inner ear, the
cochlea The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus (cochlea), modiolus. A core component of the cochlea is the Organ of Cort ...

cochlea
. The purpose of the middle ear ossicles is to overcome the impedance mismatch between air waves and cochlear waves, by providing
impedance matching In electronics Electronics comprises the physics, engineering, technology and applications that deal with the emission, flow and control of electrons in vacuum and matter. It uses active devices to control electron flow by amplifier, amplific ...
. Also located in the middle ear are the
stapedius muscle The stapedius is the smallest skeletal muscle Skeletal muscle (also called striated muscle - although cardiac muscle is also striated) is one of three major muscle types, the others being cardiac muscle and smooth muscle. It is a form of striated m ...
and
tensor tympani muscle The tensor tympani is a muscle within the middle ear, located in the bony canal above the bony part of the auditory tube, and connects to the malleus bone. Its role is to dampen loud sounds, such as those produced from mastication, chewing, shoutin ...
, which protect the hearing mechanism through a stiffening reflex. The stapes transmits sound waves to the inner ear through the
oval window The oval window (or ''fenestra vestibuli'' or ''fenestra ovalis'') is a membrane-covered opening from the middle ear to the cochlea The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, ...
, a flexible membrane separating the air-filled middle ear from the fluid-filled inner ear. The
round window The round window is one of the two openings from the middle ear The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the inner ear. The mammalian middle ear contains three ossicles, which transfer ...
, another flexible membrane, allows for the smooth displacement of the inner ear fluid caused by the entering sound waves.


Inner ear

The inner ear consists of the
cochlea The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus (cochlea), modiolus. A core component of the cochlea is the Organ of Cort ...

cochlea
, which is a spiral-shaped, fluid-filled tube. It is divided lengthwise by the
organ of Corti The organ of Corti, or spiral organ, is the receptor organ for hearing and is located in the mammalian cochlea The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.7 ...

organ of Corti
, which is the main organ of mechanical to neural transduction. Inside the organ of Corti is the
basilar membrane The basilar membrane is a stiff structural element within the cochlea The cochlea is the part of the inner ear involved in hearing. It is a spiral-shaped cavity in the bony labyrinth, in humans making 2.75 turns around its axis, the modiolus (coch ...
, a structure that vibrates when waves from the middle ear propagate through the cochlear fluid –
endolymph Endolymph is the fluid contained in the membranous labyrinth The membranous labyrinth is a collection of fluid filled tubes and chambers which contain the receptors for the senses of equilibrium and hearing. It is lodged within the bony labyrinth T ...
. The basilar membrane is
tonotopic In physiology, tonotopy (from Greek tono = frequency and topos = place) is the spatial arrangement of where sounds of different frequency are processed in the brain. Tones close to each other in terms of frequency are represented in topology, topol ...
, so that each frequency has a characteristic place of resonance along it. Characteristic frequencies are high at the basal entrance to the cochlea, and low at the apex. Basilar membrane motion causes
depolarization In biology, depolarization or hypopolarization is a change within a cell (biology), cell, during which the cell undergoes a shift in electric charge distribution, resulting in less negative charge inside the cell compared to the outside. Depolar ...
of the
hair cells Hair cells are the sensory receptor Sensory neurons, also known as afferent neurons, are neurons in the nervous system In Biology, biology, the nervous system is a Complex system, highly complex part of an animal that coordinates its Be ...
, specialized auditory receptors located within the organ of Corti. While the hair cells do not produce
action potential In physiology Physiology (; ) is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence ...

action potential
s themselves, they release neurotransmitter at synapses with the fibers of the
auditory nerve The cochlear nerve (also auditory or acoustic neuron) is one of two parts of the vestibulocochlear nerve The vestibulocochlear nerve (auditory vestibular nerve), known as the eighth cranial nerve, transmits sound and equilibrium (balance) informa ...
, which does produce action potentials. In this way, the patterns of oscillations on the basilar membrane are converted to
spatiotemporal pattern 250px, Computer simulation of the Belousov–Zhabotinsky reaction, which has non-equilibrium thermodynamics Spatialtemporal patterns are patterns that occur in a wide range of patterns in nature, natural phenoma and are characterized by a spat ...
s of firings which transmit information about the sound to the
brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and anima ...

brainstem
.


Neuronal

The sound information from the cochlea travels via the
auditory nerve The cochlear nerve (also auditory or acoustic neuron) is one of two parts of the vestibulocochlear nerve The vestibulocochlear nerve (auditory vestibular nerve), known as the eighth cranial nerve, transmits sound and equilibrium (balance) informa ...
to the
cochlear nucleus The cochlear nuclear (CN) complex comprises two Cranial nerve nucleus, cranial nerve nuclei in the human brainstem, the ventral cochlear nucleus (VCN) and the dorsal cochlear nucleus (DCN). The ventral cochlear nucleus is unlayered whereas the do ...
in the
brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and anima ...

brainstem
. From there, the signals are projected to the
inferior colliculus The inferior colliculus (IC) (Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" o ...

inferior colliculus
in the
midbrain The midbrain or mesencephalon is the forward-most portion of the brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is compose ...

midbrain
tectum The midbrain or mesencephalon is the forward-most portion of the brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is compose ...
. The
inferior colliculus The inferior colliculus (IC) (Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" o ...

inferior colliculus
integrates auditory input with limited input from other parts of the brain and is involved in subconscious reflexes such as the auditory
startle response In animals, including humans, the startle response is a largely unconscious defensive response to sudden or threatening stimuli, such as sudden noise or sharp movement, and is associated with negative affect.Rammirez-Moreno, David. "A computationa ...
. The inferior colliculus in turn projects to the
medial geniculate nucleus The medial geniculate nucleus (MGN) or medial geniculate body (MGB) is part of the auditory thalamus and represents the thalamic relay between the inferior colliculus (IC) and the auditory cortex (AC). It is made up of a number of sub-nuclei that ...
, a part of the
thalamus The thalamus (from Greek language, Greek Wikt:θάλαμος, θάλαμος, "chamber") is a large mass of gray matter located in the wikt:dorsal, dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the tha ...

thalamus
where sound information is relayed to the
primary auditory cortex The auditory cortex is the part of the temporal lobe The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals co ...
in the
temporal lobe The temporal lobe is one of the four major lobes of the cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex m ...

temporal lobe
. Sound is believed to first become consciously experienced at the
primary auditory cortex The auditory cortex is the part of the temporal lobe The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals co ...
. Around the
primary auditory cortex The auditory cortex is the part of the temporal lobe The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals co ...
lies Wernickes area, a cortical area involved in interpreting sounds that is necessary to understand spoken words. Disturbances (such as
stroke A stroke is a medical condition A disease is a particular abnormal condition that negatively affects the structure or function (biology), function of all or part of an organism, and that is not due to any immediate external injury. Di ...

stroke
or
trauma Trauma most often refers to: *Major trauma, in physical medicine, severe physical injury caused by an external source *Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic injur ...
) at any of these levels can cause hearing problems, especially if the disturbance is
bilateral Bilateral may refer to any concept including two sides, in particular: *Bilateria, bilateral animals *Bilateralism, the political and cultural relations between two states *Bilateral, occurring on both sides of an organism (Anatomical terms of loc ...
. In some instances it can also lead to
auditory hallucinations An auditory hallucination, or paracusia, is a form of hallucination that involves perceiving sounds without auditory stimulus. A common form of auditory hallucination involves hearing one or more talking voices, and this is known as an ''audit ...

auditory hallucinations
or more complex difficulties in perceiving sound.


Hearing tests

Hearing can be measured by behavioral tests using an
audiometer An audiometer is a machine used for evaluating hearing acuity. They usually consist of an embedded hardware unit connected to a pair of headphones Headphones are a pair of small Electrodynamic speaker driver, loudspeaker drivers worn on or a ...
. Electrophysiological tests of hearing can provide accurate measurements of hearing thresholds even in unconscious subjects. Such tests include auditory brainstem evoked potentials (ABR),
otoacoustic emissionsAn otoacoustic emission (OAE) is a sound In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Moti ...
(OAE) and
electrocochleography Electrocochleography (abbreviated ECochG or ECOG) is a technique of recording electrical potentials generated in the inner ear and auditory nerve in response to sound stimulation, using an electrode placed in the ear canal or tympanic membrane. The ...
(ECochG). Technical advances in these tests have allowed hearing screening for infants to become widespread. Hearing can be measured by mobile applications which includes audiological hearing test function or
hearing aid application Hearing, or auditory perception, is the ability to perceive sounds In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, ...

hearing aid application
. These applications allow the user to measure
hearing thresholds
hearing thresholds
at different frequencies (
audiogram An audiogram is a graph that shows the audible threshold for standardized frequencies as measured by an audiometer. The Y axis represents intensity measured in decibels and the X axis represents frequency measured in hertz. The threshold of hearin ...

audiogram
). Despite possible errors in measurements,
hearing loss Hearing loss is a partial or total inability to hear Hearing, or auditory perception, is the ability to perceive Sound, sounds by detecting Vibration, vibrations, changes in the pressure of the surrounding medium through time, through a ...
can be detected.


Hearing loss

There are several different types of hearing loss:
conductive hearing loss Conductive hearing loss (CHL) occurs when there is a problem transferring sound wave In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is th ...
,
sensorineural hearing loss Sensorineural hearing loss (SNHL) is a type of hearing loss Hearing loss is a partial or total inability to Hearing, hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In c ...
and mixed types. There are defined degrees of hearing loss: * Mild hearing loss - People with mild hearing loss have difficulties keeping up with conversations, especially in noisy surroundings. The most quiet sounds that people with mild hearing loss can hear with their better ear are between 25 and 40 dB HL. * Moderate hearing loss - People with moderate hearing loss have difficulty keeping up with conversations when they are not using a hearing aid. On average, the most quiet sounds heard by people with moderate hearing loss with their better ear are between 40 and 70 dB HL. * Severe hearing loss - People with severe hearing loss depend on powerful hearing aid. However, they often rely on lip-reading even when they are using hearing aids. The most quiet sounds heard by people with severe hearing loss with their better ear are between 70 and 95 dB HL. * Profound hearing loss - People with profound hearing loss are very hard of hearing and they mostly rely on lip-reading and sign language. The most quiet sounds heard by people with profound hearing loss with their better ear are from 95 dB HL or more.


Causes

*Heredity *Congenital conditions *Presbycusis *Acquired **Noise-induced hearing loss **Ototoxic drugs and chemicals **Infection


Prevention

Hearing protection is the use of devices designed to prevent
noise-induced hearing loss Noise-induced hearing loss (NIHL) is hearing impairment Hearing loss is a partial or total inability to hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, he ...
(NIHL), a type of post-lingual hearing impairment. The various means used to prevent hearing loss generally focus on reducing the levels of noise to which people are exposed. One way this is done is through environmental modifications such as
acoustic quieting Acoustic may refer to: Music Albums * ''Acoustic'' (Bayside EP) * ''Acoustic'' (Britt Nicole EP) * ''Acoustic'' (Joey Cape and Tony Sly album), 2004 * ''Acoustic'' (Coldplay EP), 2000 * ''Acoustic'' (Deine Lakaien album), 1995 * ''Acoustic' ...
, which may be achieved with as basic a measure as lining a room with
curtain A curtain is a piece of cloth or other material intended to block or obscure light, air drafts, or (in the case of a shower curtain), water. A curtain is also the movable screen or theater curtain, drape in a theater that separates the stage from ...

curtain
s, or as complex a measure as employing an
anechoic chamber An anechoic chamber (''an-echoic'' meaning "non-reflective, non-echoing, echo-free") is a room designed to completely absorb reflections of either sound or electromagnetic waves. They are also often isolated from waves entering from their s ...

anechoic chamber
, which absorbs nearly all sound. Another means is the use of devices such as
earplug An earplug is a device that is inserted in the ear canal The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear The outer ear, external ear, or auris externa is the external part of ...

earplug
s, which are inserted into the ear canal to block noise, or
earmuffs Earmuffs are clothing accessories or PPE designed to cover a person's ears for Ear protection, hearing protection or for warmth. They consist of a plastic, thermoplastic or metal head-band, that fits over the top or back of the Human head, head, ...
, objects designed to cover a person's ears entirely.


Management

The loss of hearing, when it is caused by neural loss, cannot presently be cured. Instead, its effects can be mitigated by the use of audioprosthetic devices, i.e. hearing assistive devices such as
hearing aid A hearing aid is a device designed to improve hearing by making sound audible to a person with hearing loss Hearing loss is a partial or total inability to hear Hearing, or auditory perception, is the ability to perceive Sound, soun ...
s and
cochlear implants A cochlear implant (CI) is a surgically implanted Neuroprosthetics, neuroprosthesis that provides a person who has bilateral moderate-to-profound sensorineural hearing loss with sound perception and an opportunity with therapy for improved speech u ...
. In a clinical setting, this management is offered by otologists and
audiologists Audiology (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman R ...
.


Relation to health

Hearing loss Hearing loss is a partial or total inability to hear Hearing, or auditory perception, is the ability to perceive Sound, sounds by detecting Vibration, vibrations, changes in the pressure of the surrounding medium through time, through a ...
is associated with
Alzheimer's disease Alzheimer's disease (AD), also referred to simply as Alzheimer's, is a that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of . The most common early symptom is difficulty in . As the disease advance ...
and
dementia Dementia manifests as a set of related symptoms, which usually surface when the brain is damaged by injury or disease. The symptoms Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or ...
with a greater degree of
hearing loss Hearing loss is a partial or total inability to hear Hearing, or auditory perception, is the ability to perceive Sound, sounds by detecting Vibration, vibrations, changes in the pressure of the surrounding medium through time, through a ...
tied to a higher risk. There is also an association between
type 2 diabetes Type 2 diabetes (T2D), formerly known as adult-onset diabetes, is a form of diabetes Diabetes mellitus (DM), commonly known as diabetes, is a group of metabolic disorders characterized by a high blood sugar level over a prolonged period of ...
and
hearing loss Hearing loss is a partial or total inability to hear Hearing, or auditory perception, is the ability to perceive Sound, sounds by detecting Vibration, vibrations, changes in the pressure of the surrounding medium through time, through a ...
.


Hearing underwater

Hearing threshold and the ability to localize sound sources are reduced underwater in humans, but not in aquatic animals, including whales, seals, and fish which have ears adapted to process water-borne sound.


In vertebrates

Not all sounds are normally audible to all animals. Each species has a range of normal hearing for both amplitude and
frequency Frequency is the number of occurrences of a repeating event per unit of time A unit of time is any particular time Time is the indefinite continued sequence, progress of existence and event (philosophy), events that occur in an apparen ...

frequency
. Many animals use sound to communicate with each other, and hearing in these species is particularly important for survival and reproduction. In species that use sound as a primary means of communication, hearing is typically most acute for the range of pitches produced in calls and speech.


Frequency range

Frequencies capable of being heard by humans are called
audio Audio most commonly refers to sound In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion ( ...
or sonic. The range is typically considered to be between 20 Hz and 20,000 Hz. Frequencies higher than audio are referred to as
ultrasonic
ultrasonic
, while frequencies below audio are referred to as
infrasonic Infrasound, sometimes referred to as low status sound , describes sound waves with a frequency below the lower limit of human audibility (generally 20 Hz). Hearing becomes gradually less sensitive as frequency decreases, so for humans to per ...
. Some
bats Bats are mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meanin ...

bats
use ultrasound for
echolocation
echolocation
while in flight.
Dog The dog or domestic dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a Domestication, domesticated descendant of the wolf which is characterized by an upturning tail. The dog Origin of the domestic dog, derived from an Pleistocene ...

Dog
s are able to hear ultrasound, which is the principle of 'silent'
dog whistle A dog whistle (also known as silent whistle or Galton's whistle) is a type of whistle A whistle is an instrument which produces sound from a stream of gas, most commonly air. It may be mouth-operated, or powered by air pressure, steam, or oth ...

dog whistle
s.
Snake Snakes are elongated, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Many species of snakes ...

Snake
s sense infrasound through their jaws, and baleen
whale Whales are a widely distributed and diverse group of fully aquatic Aquatic means relating to water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is ...

whale
s,
giraffe The giraffe is a tall African mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands which in Fe ...

giraffe
s,
dolphin Dolphin is the common name of aquatic mammal Aquatic and semiaquatic mammals are a diverse group of mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mam ...

dolphin
s and
elephant Elephants are the largest existing land animals. Three living species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A specie ...

elephant
s use it for communication. Some
fish Fish are aquatic Aquatic means relating to water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the ...

fish
have the ability to hear more sensitively due to a well-developed, bony connection between the ear and their swim bladder. This "aid to the deaf" for fishes appears in some species such as
carp Carp are various species of oily fish, oily freshwater fish from the family Cyprinidae, a very large group of fish native to Europe and Asia. While carp is consumed in many parts of the world, they are generally considered an invasive species in ...

carp
and
herring Herring are forage fish Forage fish, also called prey fish or bait fish, are small pelagic fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals. Typical ocean forage fish feed ...

herring
.


In invertebrates

Even though they don’t have ears, invertebrates have developed other structures and systems to decode vibrations traveling through the air, or “sound.”
Charles Henry Turner (zoologist) Charles Henry Turner (February 3, 1867 – February 14, 1923) was an American zoologist Zoology ()The pronunciation of zoology as is typically regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the animal ...
was the first scientist to formally show this phenomenon through rigorously controlled experiments in ants. Turner ruled out the detection of ground vibration and suggested that other insects likely have auditory systems as well. Many insects detect sound through the way air vibrations deflect hairs along their body. Some insects have even developed specialized hairs tuned to detecting particular frequencies, such as certain caterpillar species that have evolved hair with properties such that it resonates most with the sound of buzzing wasps, thus warning them of the presence of natural enemies. Tautz, Jürgen, and Michael Rostás. "Honeybee buzz attenuates plant damage by caterpillars." Current Biology 18, no. 24 (2008): R1125-R1126. Some insects possess a
tympanal organ A tympanal organ (or tympanic organ) is a hearing organ in insects Insects or Insecta (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originall ...
. These are "eardrums", that cover air filled chambers on the legs. Similar to the hearing process with vertebrates, the eardrums react to sonar waves. Receptors that are placed on the inside translate the oscillation into electric signals and send them to the brain. Several groups of flying insects that are preyed upon by
echolocating
echolocating
bat Bats are mammal Mammals (from Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the po ...

bat
s can perceive the ultrasound emissions this way and reflexively practice
ultrasound avoidanceUltrasound avoidance is an escape or avoidance reflex displayed by certain animal species that are preyed upon by animal echolocation, echolocating predators. Ultrasound avoidance is known for several groups of insects that have independently evolved ...
.


See also


Physiological

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Ear The ear is the organ of hearing and, in mammals, balance. In mammals, the ear is usually described as having three parts—the outer ear The outer ear, external ear, or auris externa is the external part of the ear, which consists ...

Ear
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Hearing loss Hearing loss is a partial or total inability to hear Hearing, or auditory perception, is the ability to perceive Sound, sounds by detecting Vibration, vibrations, changes in the pressure of the surrounding medium through time, through a ...
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Hearing test A hearing test provides an evaluation of the sensitivity of a person's sense of hearing and is most often performed by an audiologist using an audiometer. An audiometer is used to determine a person's hearing sensitivity at different frequencie ...


General

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Auditory scene analysis In perception Perception (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. T ...
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Auditory science Auditory science or hearing science is a field of research and education concerning the perception of sounds by humans, animals, or machines. It is a heavily interdisciplinary field at the crossroad between acoustics Acoustics is a branch of phys ...
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Auditory system The auditory system is the sensory system The sensory nervous system is a part of the nervous system responsible for processing sensory information. A sensory system consists of sensory neurons (including the sensory receptor cells), neur ...
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Bone conduction Bone conduction is the wikt:conduction, conduction of sound to the inner ear primarily through the bones of the human skull, skull, allowing the hearer to perceive audio content without blocking the ear canal. Bone conduction transmission occurs c ...

Bone conduction
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Hearing range Hearing range describes the range of frequencies that can be Hearing (sense), heard by humans or other animals, though it can also refer to the Sound pressure, range of levels. The human range is commonly given as 20 to 20,000 hertz, Hz, a ...
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Human echolocation Human echolocation is the ability of humans to detect objects in their environment by sensing echoes from those objects, by actively creating sounds: for example, by tapping their canes, lightly stomping their foot, snapping their fingers, or makin ...
* Listening * Neuronal encoding of sound * Temporal envelope and fine structure *World Hearing Day *Safe listening


Test and measurement

* Audiogram * Audiometry * Dichotic listening (test) * Auditory brainstem response (test)


Disorders

* Auditory processing disorder * Endaural phenomena *
Hearing loss Hearing loss is a partial or total inability to hear Hearing, or auditory perception, is the ability to perceive Sound, sounds by detecting Vibration, vibrations, changes in the pressure of the surrounding medium through time, through a ...
* Hyperacusis * Presbycusis * Tinnitus


References


Further reading

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External links


World Health Organization, Deafness and Hearing Loss
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Open University - OpenLearn - Article about hearing
{{DEFAULTSORT:Hearing (Sense) Hearing, Sound Audiology Auditory system