Hearing range
Encyclopedia
For more detail on human hearing see Audiogram
, Equal loudness contours and Hearing impairment
.
Hearing range usually describes the range of frequencies that can be heard by an animal or human, though it can also refer to the range of levels. In humans the audible range of frequencies is usually said to be 20 Hz
(cycles per second) to 20 kHz (20,000 Hz), although there is considerable variation between individuals, especially at the high frequency end, where a gradual decline with age is considered normal. Sensitivity also varies a lot with frequency, as shown by equal-loudness contours, which are normally only measured for research purposes, or detailed investigation. Routine investigation for hearing loss usually involves an audiogram
which shows threshold levels relative to a standardised norm.
, and this allows different frequencies to be presented to the subject, usually over calibrated headphones, at any specified level. The levels are, however, not absolute, but weighted with frequency relative to a standard graph known as the minimum audibility curve
which is intended to represent 'normal' hearing. This is not the best threshold found for all subjects, under ideal test conditions, which is represented by around 0 Phon
or the threshold of hearing on the equal-loudness contours, but is standardised in an ANSI
standard to a level somewhat higher at 1 kHz. There are several definitions of the minimal audibility curve, defined in different international standards, and they differ significantly, giving rise to differences in audiograms according to the audiometer used. The ASA-1951 standard for example used a level of 16.5 dB SPL (Sound Pressure Level) at 1 kHz whereas the later ANSI-1969/ISO-1963 standard uses 6.5 dB SPL, and it is common to allow a 10 dB correction for older people.
Hearing thresholds of humans unable to cooperate fully in audiometric testing, and other mammals can be found by using behavioural hearing tests or physiological tests.
An audiogram can be obtained using a behavioural hearing test called Audiometry. For humans the test involves different tones being presented at a specific frequency (pitch
) and intensity (loudness
). When the person hears the sound they raise their hand or press a button so that the tester knows that they have heard it. The lowest intensity sound they can hear is recorded.
The test varies for children; their response to the sound can be a head turn or using a toy. The child learns what they can do when they hear the sound, for example they are taught that when they heard the sound they can put the toy man in the boat. A similar technique can be used when testing some animals but instead of a toy food can be used as a reward for responding to the sound.
Physiological tests do not need the patient to respond (Katz 2002). For example when performing the brainstem auditory evoked potentials
the patient’s brainstem responses are being measured when a sound is played into their ear.
The information on different mammals' hearing was obtained primarily by behavioural hearing tests.
In a human
, sound waves funnel into the ear via the external ear canal and hit the eardrum
(tympanic membrane). Consequently the compression and rarefaction
of the wave set this thin membrane in motion, causing the middle ear bones (the ossicles
; malleus, incus and stapes) to move. The number of sound pressure level vibrations (sonic waves) per second denotes the frequency
. Infrasonic (below hearing), sonic (aural), and ultrasonic (above hearing) frequencies are measured in Hertz (Hz); one Hertz is one cycle wave (or singular pressure wave in audionics) per second. Specifically, humans have a maximum aural range that begins as low as 12 Hz under ideal laboratory conditions, to 20,000 Hz in most children and some adults, but the range shrinks during life, usually beginning at around the age of 8 with the higher frequencies fading. Inaudible sound waves can be detected (felt) by humans through physical body vibration in the range of 4 to 16 Hz. There is a difference in sensitivity of hearing between the sexes, with women typically having a higher sensitivity to higher frequencies than men (Gotfrit 1995).
The vibrations of the ossicular chain displace the basilar fluid in the cochlea, causing the hairs within it, called Stereocilia, to vibrate. Hairs line the cochlea from base to apex, and the part stimulated and the intensity of stimulation gives an indication of the nature of the sound. Information gathered from the hair cells is sent via the auditory nerve for processing in the brain.
s exploit this phenomenon by producing sounds at frequencies higher than those audible to humans but well within the range of a dog's hearing.
When compressing a digital signal, an acoustic engineer
can safely assume that any frequency beyond approximately 20 kHz will not have any effect on the perceived sound of the finished product, and thus use a low pass filter to cut everything outside this range. The sound can then be sampled at the standard CD sample rate of 44.1 kHz (or 48 kHz in DAT
), set somewhat higher than the calculated Nyquist-Shannon rate of 40 kHz to allow for the cut-off slope of a reasonable low pass filter.
When additional compression of sound is required, higher frequencies are usually cut off first, because regular adults' hearing in those areas is often even less than 20 kHz. This is due to loss of hearing in the high-frequency range, due to either hearing damage (e.g. from listening to loud music) or aging. For instance, the commonly used MP3
coding often cuts sounds above 18 kHz, or when compressing as high as 128 kbit/s, at 16 kHzhttp://xs.vc/eac/Spectral/spectral.html.
is dependent on its breed and age. However, the range of hearing is approximately 40 Hz to 60,000 Hz, which is much greater than that of humans. As with humans, some dog breeds become more deaf with age, such as the German Shepherd and Miniature Poodle. When dogs hear a sound, they will move their ears towards it in order to maximise reception. In order to achieve this, the ears of a dog are controlled by at least 18 muscles. This allows the ears to tilt and rotate. Ear shape also allows for the sound to be more accurately heard. Many breeds often have upright and curved ears, which direct and amplify the sounds.
As dogs hear much higher frequency sounds than humans, they have a different acoustic perception of the world. Sounds that seem loud to humans often emit high frequency tones that can scare away dogs. Ultrasonic signals are used in training whistles
, as a dog will respond much better to such levels. In the wild, dogs use their hearing capabilities to hunt and locate food. Domestic breeds are often used as guard dogs due to their increased hearing ability (Condon 2003).
s require very sensitive hearing to compensate for their lack of visual stimuli, particularly in a hunting situation, and for navigation. Their hearing range is between 20 Hz and 120,000 Hz. They locate their prey by means of echolocation. A bat will produce a very loud, short sound and assess the echo when it bounces back. The type of insect and how big it is can be determined by the quality of the echo and time it takes for the echo to rebound; there are two types; constant frequency (CF), and frequency modulated (FM) calls that descend in pitch (Bennu 2001). Each type reveals different information for the bat; CF is used to detect an object, and FM is used to provide information regarding the nature of the object and its distance.
The pulses of sound produced by the bat last only a few thousandths of a second; silences between the calls give time to listen for the information coming back in the form of an echo. There is also evidence to suggest that bats use the change in pitch of sound produced (the Doppler effect
) to assess their flight speed
in relation to objects around them (Richardson n.d).
The information regarding size, shape and texture is built up to form a picture of their surroundings and the location of their prey. Using these factors a bat can successfully track change in movements and therefore hunt down their prey.
have large ears in comparison to their bodies. Mice hear higher frequencies than humans; their frequency range is 1 kHz to 70 kHz or 90 kHz. They do not hear the lower frequencies that we can; they communicate using high frequency noises some of which are inaudible by humans. The distress call of a young mouse
can be produced at 40 kHz. The mice use their ability to produce and hear sounds out of our and other predators' frequency ranges to their advantage. They can alert other mice of danger without also alerting the predator to their presence. The squeaks that we can hear a mouse make are lower in frequency and are used by the mouse to make longer distance calls, as the low frequency sound can travel further than the high frequency
sounds (Lawlor).
s have led to extensive research on aquatic mammals, specifically on various kinds of dolphins.
The auditory system of a land mammal typically works via the transfer of sound waves through the ear canals. Ear canals in the pinnipeds or seals
, sea lions, and walruses, are similar to those of land mammals and may function the same way. In whales and dolphins, it is not entirely clear how sound is propagated to the ear, but some studies strongly suggest that sound is channeled to the ear by tissues in the area of the lower jaw. One group of whales, the Odontocetes or toothed whales, use the process of echolocation
to determine the position of objects, such as prey. The toothed whales are also unusual in that the ears are separated from the skull and placed well apart, which assists them with localizing sounds, an important element for echolocation.
Studies (Ketten and Wartzok 1990) have found there to be two different types of cochlea
in the dolphin population. Type I has been found in the Amazon River dolphin and harbour porpoises. These types of dolphin use extremely high frequency signals for echolocation. It has been found that the harbour porpoise emits sounds at two bands, one at 2 kHz and one above 110 kHz. The cochlea in these dolphins is specialised to accommodate extreme high frequency sounds and is extremely narrow at the base of the cochlea.
Type II cochlea are found primarily in offshore and open water species of whales, such as the bottlenose dolphin. The sounds produced by bottlenose dolphins are lower in frequency and range typically between 0.25 to 150 kHz. The higher frequencies in this range are also used for echolocation and the lower frequencies are commonly associated with social interaction as the signals travel much further distances.
Marine mammals use vocalizations in many different ways. Dolphins communicate via clicks and whistles, and whales use low frequency moans or pulse signals. Each signal varies in terms of frequency and different signals are used to communicate different aspects. In dolphins, echolocation is used in order to detect and characterize objects and whistles are used in sociable herds as identification and communication devices.
Audiogram
An audiogram is a standard way of representing a person's hearing loss . Most audiograms cover the limited range 100 Hz to 8000 Hz which is most important for clear understanding of speech, and they plot the threshold of hearing relative to a standardised curve that represents 'normal'...
, Equal loudness contours and Hearing impairment
Hearing impairment
-Definition:Deafness is the inability for the ear to interpret certain or all frequencies of sound.-Environmental Situations:Deafness can be caused by environmental situations such as noise, trauma, or other ear defections...
.
Hearing range usually describes the range of frequencies that can be heard by an animal or human, though it can also refer to the range of levels. In humans the audible range of frequencies is usually said to be 20 Hz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
(cycles per second) to 20 kHz (20,000 Hz), although there is considerable variation between individuals, especially at the high frequency end, where a gradual decline with age is considered normal. Sensitivity also varies a lot with frequency, as shown by equal-loudness contours, which are normally only measured for research purposes, or detailed investigation. Routine investigation for hearing loss usually involves an audiogram
Audiogram
An audiogram is a standard way of representing a person's hearing loss . Most audiograms cover the limited range 100 Hz to 8000 Hz which is most important for clear understanding of speech, and they plot the threshold of hearing relative to a standardised curve that represents 'normal'...
which shows threshold levels relative to a standardised norm.
Determination of hearing thresholds
Audiograms in humans are produced using a piece of test equipment called an audiometerAudiometer
An audiometer is a machine used for evaluating hearing loss. Audiometers are standard equipment at ENT clinics and in audiology centers. They usually consist of an embedded hardware unit connected to a pair of headphones and a test subject feedback button, sometimes controlled by a standard PC...
, and this allows different frequencies to be presented to the subject, usually over calibrated headphones, at any specified level. The levels are, however, not absolute, but weighted with frequency relative to a standard graph known as the minimum audibility curve
Minimum audibility curve
Minimum audibility curve is a standardised graph of the threshold of hearing versus frequency for an average human, and is used as the reference level when measuring hearing loss with an audiometer as shown on an audiogram....
which is intended to represent 'normal' hearing. This is not the best threshold found for all subjects, under ideal test conditions, which is represented by around 0 Phon
Phon
The phon was proposed in DIN 45631 and ISO 532 B as a unit of perceived loudness level LN for pure tones by S. S. Stevens.-Definition:The purpose of the phon scale is to compensate for the effect of frequency on the perceived loudness of tones...
or the threshold of hearing on the equal-loudness contours, but is standardised in an ANSI
Ansi
Ansi is a village in Kaarma Parish, Saare County, on the island of Saaremaa, Estonia....
standard to a level somewhat higher at 1 kHz. There are several definitions of the minimal audibility curve, defined in different international standards, and they differ significantly, giving rise to differences in audiograms according to the audiometer used. The ASA-1951 standard for example used a level of 16.5 dB SPL (Sound Pressure Level) at 1 kHz whereas the later ANSI-1969/ISO-1963 standard uses 6.5 dB SPL, and it is common to allow a 10 dB correction for older people.
Hearing thresholds of humans unable to cooperate fully in audiometric testing, and other mammals can be found by using behavioural hearing tests or physiological tests.
An audiogram can be obtained using a behavioural hearing test called Audiometry. For humans the test involves different tones being presented at a specific frequency (pitch
Pitch (music)
Pitch is an auditory perceptual property that allows the ordering of sounds on a frequency-related scale.Pitches are compared as "higher" and "lower" in the sense associated with musical melodies,...
) and intensity (loudness
Loudness
Loudness is the quality of a sound that is primarily a psychological correlate of physical strength . More formally, it is defined as "that attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud."Loudness, a subjective measure, is often...
). When the person hears the sound they raise their hand or press a button so that the tester knows that they have heard it. The lowest intensity sound they can hear is recorded.
The test varies for children; their response to the sound can be a head turn or using a toy. The child learns what they can do when they hear the sound, for example they are taught that when they heard the sound they can put the toy man in the boat. A similar technique can be used when testing some animals but instead of a toy food can be used as a reward for responding to the sound.
Physiological tests do not need the patient to respond (Katz 2002). For example when performing the brainstem auditory evoked potentials
Brainstem auditory evoked potentials
Brainstem Auditory evoked potentials are very small electrical voltage potentials which are recorded in response to an auditory stimulus from electrodes placed on the scalp. They reflect neuronal activity in the auditory nerve, cochlear nucleus, superior olive and inferior colliculus of the...
the patient’s brainstem responses are being measured when a sound is played into their ear.
The information on different mammals' hearing was obtained primarily by behavioural hearing tests.
Land mammals
The following sections describe the frequency range of a specific mammal's hearing in comparison to other mammals. Low pitch sounds are low in frequency; the high pitch sounds are high in frequency.Humans
Human
Humans are the only living species in the Homo genus...
, sound waves funnel into the ear via the external ear canal and hit the eardrum
Eardrum
The eardrum, or tympanic membrane, is a thin membrane that separates the external ear from the middle ear in humans and other tetrapods. Its function is to transmit sound from the air to the ossicles inside the middle ear. The malleus bone bridges the gap between the eardrum and the other ossicles...
(tympanic membrane). Consequently the compression and rarefaction
Rarefaction
Rarefaction is the reduction of a medium's density, or the opposite of compression.A natural example of this is as a phase in a sound wave or phonon. Half of a sound wave is made up of the compression of the medium, and the other half is the decompression or rarefaction of the medium.Another...
of the wave set this thin membrane in motion, causing the middle ear bones (the ossicles
Ossicles
The ossicles are the three smallest bones in the human body. They are contained within the middle ear space and serve to transmit sounds from the air to the fluid-filled labyrinth . The absence of the auditory ossicles would constitute a moderate-to-severe hearing loss...
; malleus, incus and stapes) to move. The number of sound pressure level vibrations (sonic waves) per second denotes the frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
. Infrasonic (below hearing), sonic (aural), and ultrasonic (above hearing) frequencies are measured in Hertz (Hz); one Hertz is one cycle wave (or singular pressure wave in audionics) per second. Specifically, humans have a maximum aural range that begins as low as 12 Hz under ideal laboratory conditions, to 20,000 Hz in most children and some adults, but the range shrinks during life, usually beginning at around the age of 8 with the higher frequencies fading. Inaudible sound waves can be detected (felt) by humans through physical body vibration in the range of 4 to 16 Hz. There is a difference in sensitivity of hearing between the sexes, with women typically having a higher sensitivity to higher frequencies than men (Gotfrit 1995).
The vibrations of the ossicular chain displace the basilar fluid in the cochlea, causing the hairs within it, called Stereocilia, to vibrate. Hairs line the cochlea from base to apex, and the part stimulated and the intensity of stimulation gives an indication of the nature of the sound. Information gathered from the hair cells is sent via the auditory nerve for processing in the brain.
Effects of high frequency limit
So-called "silent" dog whistleDog whistle
A dog whistle is a type of whistle used in the training of dogs and cats. It was invented by Francis Galton. This is discussed quite briefly in his book Inquiries into Human Faculty and its Development...
s exploit this phenomenon by producing sounds at frequencies higher than those audible to humans but well within the range of a dog's hearing.
When compressing a digital signal, an acoustic engineer
Acoustical engineering
Acoustical engineering is the branch of engineering dealing with sound and vibration. It is the application of acoustics, the science of sound and vibration, in technology. Acoustical engineers are typically concerned with the manipulation and control of sound....
can safely assume that any frequency beyond approximately 20 kHz will not have any effect on the perceived sound of the finished product, and thus use a low pass filter to cut everything outside this range. The sound can then be sampled at the standard CD sample rate of 44.1 kHz (or 48 kHz in DAT
Digital Audio Tape
Digital Audio Tape is a signal recording and playback medium developed by Sony and introduced in 1987. In appearance it is similar to a compact audio cassette, using 4 mm magnetic tape enclosed in a protective shell, but is roughly half the size at 73 mm × 54 mm × 10.5 mm. As...
), set somewhat higher than the calculated Nyquist-Shannon rate of 40 kHz to allow for the cut-off slope of a reasonable low pass filter.
When additional compression of sound is required, higher frequencies are usually cut off first, because regular adults' hearing in those areas is often even less than 20 kHz. This is due to loss of hearing in the high-frequency range, due to either hearing damage (e.g. from listening to loud music) or aging. For instance, the commonly used MP3
MP3
MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression...
coding often cuts sounds above 18 kHz, or when compressing as high as 128 kbit/s, at 16 kHzhttp://xs.vc/eac/Spectral/spectral.html.
Dogs
The hearing ability of a dogDog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
is dependent on its breed and age. However, the range of hearing is approximately 40 Hz to 60,000 Hz, which is much greater than that of humans. As with humans, some dog breeds become more deaf with age, such as the German Shepherd and Miniature Poodle. When dogs hear a sound, they will move their ears towards it in order to maximise reception. In order to achieve this, the ears of a dog are controlled by at least 18 muscles. This allows the ears to tilt and rotate. Ear shape also allows for the sound to be more accurately heard. Many breeds often have upright and curved ears, which direct and amplify the sounds.
As dogs hear much higher frequency sounds than humans, they have a different acoustic perception of the world. Sounds that seem loud to humans often emit high frequency tones that can scare away dogs. Ultrasonic signals are used in training whistles
Dog whistle
A dog whistle is a type of whistle used in the training of dogs and cats. It was invented by Francis Galton. This is discussed quite briefly in his book Inquiries into Human Faculty and its Development...
, as a dog will respond much better to such levels. In the wild, dogs use their hearing capabilities to hunt and locate food. Domestic breeds are often used as guard dogs due to their increased hearing ability (Condon 2003).
Bats
BatBat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...
s require very sensitive hearing to compensate for their lack of visual stimuli, particularly in a hunting situation, and for navigation. Their hearing range is between 20 Hz and 120,000 Hz. They locate their prey by means of echolocation. A bat will produce a very loud, short sound and assess the echo when it bounces back. The type of insect and how big it is can be determined by the quality of the echo and time it takes for the echo to rebound; there are two types; constant frequency (CF), and frequency modulated (FM) calls that descend in pitch (Bennu 2001). Each type reveals different information for the bat; CF is used to detect an object, and FM is used to provide information regarding the nature of the object and its distance.
The pulses of sound produced by the bat last only a few thousandths of a second; silences between the calls give time to listen for the information coming back in the form of an echo. There is also evidence to suggest that bats use the change in pitch of sound produced (the Doppler effect
Doppler effect
The Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842 in Prague, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from...
) to assess their flight speed
Speed
In kinematics, the speed of an object is the magnitude of its velocity ; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as...
in relation to objects around them (Richardson n.d).
The information regarding size, shape and texture is built up to form a picture of their surroundings and the location of their prey. Using these factors a bat can successfully track change in movements and therefore hunt down their prey.
Mice
MiceMICE
-Fiction:*Mice , alien species in The Hitchhiker's Guide to the Galaxy*The Mice -Acronyms:* "Meetings, Incentives, Conferencing, Exhibitions", facilities terminology for events...
have large ears in comparison to their bodies. Mice hear higher frequencies than humans; their frequency range is 1 kHz to 70 kHz or 90 kHz. They do not hear the lower frequencies that we can; they communicate using high frequency noises some of which are inaudible by humans. The distress call of a young mouse
Mouse
A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...
can be produced at 40 kHz. The mice use their ability to produce and hear sounds out of our and other predators' frequency ranges to their advantage. They can alert other mice of danger without also alerting the predator to their presence. The squeaks that we can hear a mouse make are lower in frequency and are used by the mouse to make longer distance calls, as the low frequency sound can travel further than the high frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
sounds (Lawlor).
Marine mammals
Marine mammals are mammals that inhabit the oceans, bays, and some rivers. As aquatic environments have very different physical properties than land environments, there are differences in how marine mammals hear compared to land mammals. The differences in auditory systemAuditory system
The auditory system is the sensory system for the sense of hearing.- Outer ear :The folds of cartilage surrounding the ear canal are called the pinna...
s have led to extensive research on aquatic mammals, specifically on various kinds of dolphins.
The auditory system of a land mammal typically works via the transfer of sound waves through the ear canals. Ear canals in the pinnipeds or seals
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...
, sea lions, and walruses, are similar to those of land mammals and may function the same way. In whales and dolphins, it is not entirely clear how sound is propagated to the ear, but some studies strongly suggest that sound is channeled to the ear by tissues in the area of the lower jaw. One group of whales, the Odontocetes or toothed whales, use the process of echolocation
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
to determine the position of objects, such as prey. The toothed whales are also unusual in that the ears are separated from the skull and placed well apart, which assists them with localizing sounds, an important element for echolocation.
Cochlea
The cochlea is the auditory portion of the inner ear. It is a spiral-shaped cavity in the bony labyrinth, making 2.5 turns around its axis, the modiolus....
in the dolphin population. Type I has been found in the Amazon River dolphin and harbour porpoises. These types of dolphin use extremely high frequency signals for echolocation. It has been found that the harbour porpoise emits sounds at two bands, one at 2 kHz and one above 110 kHz. The cochlea in these dolphins is specialised to accommodate extreme high frequency sounds and is extremely narrow at the base of the cochlea.
Type II cochlea are found primarily in offshore and open water species of whales, such as the bottlenose dolphin. The sounds produced by bottlenose dolphins are lower in frequency and range typically between 0.25 to 150 kHz. The higher frequencies in this range are also used for echolocation and the lower frequencies are commonly associated with social interaction as the signals travel much further distances.
Marine mammals use vocalizations in many different ways. Dolphins communicate via clicks and whistles, and whales use low frequency moans or pulse signals. Each signal varies in terms of frequency and different signals are used to communicate different aspects. In dolphins, echolocation is used in order to detect and characterize objects and whistles are used in sociable herds as identification and communication devices.
See also
- AudiogramAudiogramAn audiogram is a standard way of representing a person's hearing loss . Most audiograms cover the limited range 100 Hz to 8000 Hz which is most important for clear understanding of speech, and they plot the threshold of hearing relative to a standardised curve that represents 'normal'...
- Minimum audibility curveMinimum audibility curveMinimum audibility curve is a standardised graph of the threshold of hearing versus frequency for an average human, and is used as the reference level when measuring hearing loss with an audiometer as shown on an audiogram....
- Equal-loudness contourEqual-loudness contourAn equal-loudness contour is a measure of sound pressure , over the frequency spectrum, for which a listener perceives a constant loudness when presented with pure steady tones. The unit of measurement for loudness levels is the phon, and is arrived at by reference to equal-loudness contours...
- Articulation indexArticulation indexThe Articulation Index is a tool used by audiologists to predict the amount of speech that is audible to a patient with a specific hearing loss. The AI reading for a given patient can range from zero to 1.0, representing the proportion of the average speech signal that is audible...
- Pure tone audiometryPure tone audiometryPure tone audiometry is the key hearing test used to identify hearing threshold levels of an individual, enabling determination of the degree, type and configuration of a hearing loss. Thus, providing the basis for diagnosis and management. PTA is a subjective, behavioural measurement of hearing...
- PresbycusisPresbycusisPresbycusis, or age-related hearing loss, is the cumulative effect of aging on hearing. Also known as presbyacusis, it is defined as a progressive bilateral symmetrical age-related sensorineural hearing loss. The hearing loss is most marked at higher frequencies...
- PsychoacousticsPsychoacousticsPsychoacoustics is the scientific study of sound perception. More specifically, it is the branch of science studying the psychological and physiological responses associated with sound...
- Vocal and Instrumental Pitch Ranges
- Hearing (sense)Hearing (sense)Hearing is the ability to perceive sound by detecting vibrations through an organ such as the ear. It is one of the traditional five senses...
- AudiologyAudiologyAudiology is the branch of science that studies hearing, balance, and related disorders. Its practitioners, who treat those with hearing loss and proactively prevent related damage are audiologists. Employing various testing strategies Audiology (from Latin , "to hear"; and from Greek , -logia) is...
- AudiometryAudiometryAudiometry is the testing of hearing ability, involving thresholds and differing frequencies. Typically, audiometric tests determine a subject's hearing levels with the help of an audiometer, but may also measure ability to discriminate between different sound intensities, recognize pitch, or...
- Fletcher-Munson
- A-weightingA-weightingA Weighting curve is a graph of a set of factors, that are used to 'weight' measured values of a variable according to their importance in relation to some outcome. The most commonly known example is frequency weighting in sound level measurement where a specific set of weighting curves known as A,...
- The MosquitoThe MosquitoThe Mosquito or Mosquito alarm is an electronic device, used to deter loitering by young people, which emits a sound with a very high frequency...
- Seismic communicationSeismic communicationSeismic communication describes communication through seismic vibrations of the earth. Seismic cues are generated through percussion on the earth substrate or acoustical waves that couple with the earth, called rayleigh waves.-Overview:...
External links
- Levels of hearing loss
- Audiogram - GP notebook
- Bat calls converted to a frequency we can detect
- Moving image to represent echolocalisation
- Behavioral Audiograms of Mammals (in Table Form)
- Journal articles on mammalian hearing
- Frequency Range of Human Hearing (with audio tests for high and low frequency sounds)
