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Acoustic Reflex
The acoustic reflex (also known as the stapedius reflex, stapedial reflex, auditory reflex, middle-ear-muscle reflex (MEM reflex, MEMR), attenuation reflex, cochleostapedial reflex or intra-aural reflex) is an involuntary muscle contraction that occurs in the middle ear in response to loud sound stimuli or when the person starts to vocalize. When presented with an intense sound stimulus, the stapedius and tensor tympani muscles of the ossicles contract. The stapedius stiffens the ossicular chain by pulling the stapes (stirrup) of the middle ear away from the oval window of the cochlea and the tensor tympani muscle stiffens the ossicular chain by loading the tympanic membrane when it pulls the malleus (hammer) in toward the middle ear. The reflex decreases the transmission of vibrational energy to the cochlea, where it is converted into electrical impulses to be processed by the brain. Acoustic reflex threshold The acoustic reflex threshold (ART) is the sound pressure level (SPL) ...
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Muscle
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle tissue, and are often known as muscle fibers. The muscle tissue of a skeletal muscle is striated – having a striped appearance due to the arrangement of the sarcomeres. Skeletal muscles are voluntary muscles under the control of the somatic nervous system. The other types of muscle are cardiac muscle which is also striated and smooth muscle which is non-striated; both of these types of muscle tissue are classified as involuntary, or, under the control of the autonomic nervous system. A skeletal muscle contains multiple fascicles – bundles of muscle fibers. Each individual fiber, and each muscle is surrounded by a type of connective tissue layer of fascia. Muscle fibers are formed from the fusion of developmental myoblasts ...
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Auditory Hazard Assessment Algorithm For Humans
The Auditory Hazard Assessment Algorithm for Humans (AHAAH) is a mathematical model of the human auditory system that calculates the risk to human hearing caused by exposure to impulse sounds, such as gunfire and airbag deployment. It was developed by the U.S. Army Research Laboratory (ARL) to assess the effectiveness of hearing protection devices and aid the design of machinery and weapons to make them safer for the user. In 2015, the AHAAH became one of the two metrics used by the U.S. Department of Defense to approve the Military Standard (MIL-STD) 1474E for regulating maximum noise level exposure from military systems. It is also used by the Society of Automotive Engineers to calculate the hazard of airbag noise and by the Israeli Defense Force for impulse noise analysis. Overview Noise-induced hearing loss (NIHL) typically occurs when the auditory system experiences an elevation of hearing thresholds due to exposure to high-level noise, a phenomenon known as a tempora ...
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Reflexes
In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus. Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs via neural pathways in the nervous system called reflex arcs. A stimulus initiates a neural signal, which is carried to a synapse. The signal is then transferred across the synapse to a motor neuron which evokes a target response. These neural signals do not always travel to the brain, so many reflexes are an automatic response to a stimulus that does not receive or need conscious thought. Many reflexes are fine-tuned to increase organism survival and self-defense. This is observed in reflexes such as the startle reflex, which provides an automatic response to an unexpected stimuli, and the feline righting reflex, which reorients a cat's body when falling to ensure safe landing. The simplest type of reflex, a short-latency reflex, has a ...
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Tympanometry
Tympanometry is an acoustic evaluation of the condition of the middle ear eardrum (tympanic membrane) and the conduction bones by creating variations of air pressure in the ear canal. Tympanometry is an objective test of middle-ear function. It is not a hearing test, but rather a measure of energy transmission through the middle ear. It is not a measure of TM or middle ear mobility. It is an acoustic measure, measured by a microphone, as part of the ear canal probe, inserted into the ear canal. The test should not be used to assess the sensitivity of hearing and the results of this test should always be viewed in conjunction with pure tone audiometry. Tympanometry is a valuable component of the audiometric evaluation. In evaluating hearing loss, tympanometry permits a distinction between sensorineural and conductive hearing loss, when evaluation is not apparent via Weber and Rinne testing. Furthermore, in a primary care setting, tympanometry can be helpful in making the diagnosi ...
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Stapedius Muscle
The stapedius is the smallest skeletal muscle in the human body. At just over one millimeter in length, its purpose is to stabilize the smallest bone in the body, the stapes or strirrup bone of the middle ear. Structure The stapedius emerges from a pinpoint foramen or opening in the apex of the pyramidal eminence (a hollow, cone-shaped prominence in the posterior wall of the tympanic cavity), and inserts into the neck of the stapes. Nerve supply The stapedius is supplied by the nerve to stapedius, a branch of the facial nerve. Function The stapedius dampens the vibrations of the stapes by pulling on the neck of that bone. As one of the muscles involved in the acoustic reflex it prevents excess movement of the stapes, helping to control the amplitude of sound waves from the general external environment to the inner ear. Clinical significance Paralysis of the stapedius allows wider oscillation of the stapes, resulting in heightened reaction of the auditory ossicles to s ...
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Hyperacusis
Hyperacusis is the increased sensitivity to sound and a low tolerance for environmental noise. Definitions of hyperacusis can vary significantly; it can refer to normal noises being perceived as: loud, annoying, painful, fear-inducing, or a combination of those, and is often categorized into four subtypes: loudness, pain, annoyance, and fear. It can be a highly debilitating hearing disorder. Hyperacusis is often coincident with tinnitus. The latter is more common and there are important differences between their involved mechanisms. Little is known about the prevalence of hyperacusis, in part due to the degree of variation in the term's definition. Reported prevalence in children and adolescents ranges from 3% to 17%. Signs and symptoms In hyperacusis, the symptoms are ear pain, annoyance, distortions, and general intolerance to many sounds that most people are unaffected by. Crying spells or panic attacks may result from the experience of hyperacusis. It may affect only one o ...
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Audiometry
Audiometry () is a branch of audiology and the science of measuring hearing acuity for variations in sound intensity and pitch and for tonal purity, 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 distinguish speech from background noise. Acoustic reflex and otoacoustic emissions may also be measured. Results of audiometric tests are used to diagnose hearing loss or diseases of the ear, and often make use of an audiogram. History The basic requirements of the field were to be able to produce a repeating sound, some way to attenuate the amplitude, a way to transmit the sound to the subject, and a means to record and interpret the subject's responses to the test. Mechanical "acuity meters" and tuning forks For many years there was desultory use of various devices capable of pro ...
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Equal-loudness Contours
An equal-loudness contour is a measure of sound pressure level, 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. By definition, two sine waves of differing frequencies are said to have equal-loudness level measured in phons if they are perceived as equally loud by the average young person without significant hearing impairment. The Fletcher–Munson curves are one of many sets of equal-loudness contours for the human ear, determined experimentally by Harvey Fletcher and Wilden A. Munson, and reported in a 1933 paper entitled "Loudness, its definition, measurement and calculation" in the ''Journal of the Acoustical Society of America''. Fletcher–Munson curves have been superseded and incorporated into newer standards. The definitive curves are those defined in ISO 226 from the International Orga ...
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Otoacoustic Emission
An otoacoustic emission (OAE) is a sound that is generated from within the inner ear. Having been predicted by Austrian astrophysicist Thomas Gold in 1948, its existence was first demonstrated experimentally by British physicist David Kemp in 1978, and otoacoustic emissions have since been shown to arise through a number of different cellular and mechanical causes within the inner ear. Studies have shown that OAEs disappear after the inner ear has been damaged, so OAEs are often used in the laboratory and the clinic as a measure of inner ear health. Broadly speaking, there are two types of otoacoustic emissions: spontaneous otoacoustic emissions (SOAEs), which occur without external stimulation, and evoked otoacoustic emissions (EOAEs), which require an evoking stimulus. Mechanism of occurrence OAEs are considered to be related to the amplification function of the cochlea. In the absence of external stimulation, the activity of the cochlear amplifier increases, leading to the pr ...
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Tensor Tympani
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 chewing, shouting, or thunder. Because its reaction time is not fast enough, the muscle cannot protect against hearing damage caused by sudden loud sounds, like explosions or gunshots. Structure The tensor tympani is a muscle that is present in the middle ear. It arises from the cartilaginous part of the auditory tube, and the adjacent great wing of the sphenoid. It then passes through its own canal, and ends in the tympanic cavity as a slim tendon that connects to the handle of the malleus. The tendon makes a sharp bend around the ''processus cochleariformis'', part of the wall of its cavity, before it joins with the malleus. The tensor tympani receives blood from the middle meningeal artery via the superior tympanic branch. It is one of two muscles in th ...
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Facial Nerve
The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue. The nerve typically travels from the pons through the facial canal in the temporal bone and exits the skull at the stylomastoid foramen. It arises from the brainstem from an area posterior to the cranial nerve VI (abducens nerve) and anterior to cranial nerve VIII (vestibulocochlear nerve). The facial nerve also supplies preganglionic parasympathetic fibers to several head and neck ganglia. The facial and intermediate nerves can be collectively referred to as the nervus intermediofacialis. The path of the facial nerve can be divided into six segments: # intracranial (cisternal) segment # meatal (canalicular) segment (within the internal auditory canal) # labyrinthine segment (i ...
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LDV AR Measurement USAARL
LDV may refer to: *LDV Group, formerly Leyland DAF Vans, UK ** The Football League Trophy was called LDV Vans Trophy 2000-2007 * LDV USA Manufacturer of the iconic Snap-on vans & Custom Specialty Vehicles in USA *Local Defence Volunteers, renamed Home Guard (United Kingdom) *Lansing Derby Vixens, a roller derby league, Michigan, US *Laser Doppler vibrometer, for measuring vibration * Lactate dehydrogenase elevating virus *Lisa De Vanna, an Australian soccer player *Leonardo da Vinci Leonardo di ser Piero da Vinci (15 April 14522 May 1519) was an Italian polymath of the High Renaissance who was active as a painter, Drawing, draughtsman, engineer, scientist, theorist, sculptor, and architect. While his fame initially res ... In transport: * Light Duty Vehicle, a light commercial vehicle ** “Light delivery vehicle” in South Africa: motor vehicle designed or adapted for the conveyance of persons and freight with no heavy axle. {{disambig ...
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