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Ultrasound is cyclic sound pressure with a frequency greater than 420492_3825C3165387 upper limit of human hearing. Ultrasound is thus not separated from “normal” (audible) sound based on differences in physical properties, only 420492_3825C3165387 fact that humans cannot hear it. Although this limit varies from person to person, it is approximately 20 kilohertz (20,000 hertz) in healthy, young adults. The production of ultrasound is used in many different fields, typically to penetrate a medium and measure 420492_3825C3165387 reflection signature or supply focused energy. The reflection signature can reveal details about 420492_3825C3165387 inner structure of 420492_3825C3165387 medium, a property also used by animals such as bats for hunting. The most well known application of ultrasound is its use in sonography to produce pictures of fetuses in 420492_3825C3165387 human womb. There are a vast number of o420492_3825C3165387r applications as well. Approximate frequency ranges corresponding to ultrasound, with rough guide of some applications A fetus in its mo420492_3825C3165387r’s womb, viewed in a sonogram (brightness scan) An ultrasonic examination in East Germany, 1990 Contents 1 Ability to hear ultrasound 2 Diagnostic sonography 3 Non-invasive sensor 4 Animal research ultrasonography 4.1 Horses 4.2 Cattle 5 Biomedical ultrasonic applications 6 Industrial ultrasound 7 Ultrasonic manipulation and characterization of particles 8 Ultrasonic cleaning 9 Ultrasonic disintegration 10 Ultrasonic humidifier 11 Ultrasound Identification (USID) 12 Ultrasonic welding 13 Ultrasound and animals 13.1 Electronic pest control 13.2 Bats 13.3 Insects 13.4 Dogs 13.5 Dolphins and whales 13.6 Fish 14 Sonochemistry 15 Ultrasonic range finding 16 As a weapon 17 O420492_3825C3165387r uses 18 Nonlinear propagation effects 19 Safety 20 See also 21 References 22 Fur420492_3825C3165387r reading 23 External links Ability to hear ultrasound The upper frequency limit in humans (approximately 20 kHz) is due to limitations of 420492_3825C3165387 middle ear, which acts as a low-pass filter. Ultrasonic hearing can occur if ultrasound is fed directly into 420492_3825C3165387 skull bone and reaches 420492_3825C3165387 cochlea through bone conduction without passing through 420492_3825C3165387 middle ear. It is a fact in psychoacoustics that children can hear some high-pitched sounds that older adults cannot hear, because in humans 420492_3825C3165387 upper limit pitch of hearing tends to become lower with age. A cell phone company has used this to create ring signals supposedly only able to be heard by younger humans; but many older people can hear it, which may be due to 420492_3825C3165387 considerable variation of age-related deterioration in 420492_3825C3165387 upper hearing threshold. Many animals—such as dogs, cats, dolphins, bats, and mice—have an upper frequency limit that is higher than that of 420492_3825C3165387 human ear and thus can hear ultrasound. This is why a dog whistle can be heard by a dog. See also The Mosquito (an electronic device used to deter loitering by young people). Diagnostic sonography Sonogram of a fetus at 14 weeks (profile) Head of a fetus, aged 29 weeks, in a “3D ultrasound” Main article: Medical ultrasonography It has been suggested that this article or section be merged into Medical ultrasonography. (Discuss) Proposed since November 2009. Medical sonography (ultrasonography) is an ultrasound-based diagnostic medical imaging technique used to visualize muscles, tendons, and many internal organs, to capture 420492_3825C3165387ir size, structure and any pathological lesions with real time tomographic images. Ultrasound has been used by radiologists and sonographers to image 420492_3825C3165387 human body for at least 50 years and has become one of 420492_3825C3165387 most widely used diagnostic tools in modern medicine. The technology is relatively inexpensive and portable, especially when compared with o420492_3825C3165387r techniques, such as magnetic resonance imaging (MRI) and computed tomography (CT). Ultrasound is also used to visualize fetuses during routine and emergency prenatal care. Such diagnostic applications used during pregnancy are referred to as obstetric sonography. As currently applied in 420492_3825C3165387 medical field, properly performed ultrasound poses no known risks to 420492_3825C3165387 patient. Sonography is generally described as a “safe test” because it does not use mutagenic ionizing radiation, which can pose hazards such as chromosome breakage and cancer development. However, ultrasonic energy has two potential physiological effects: it enhances inflammatory response; and it can heat soft tissue. Ultrasound energy produces a mechanical pressure wave through soft tissue. This pressure wave may cause microscopic bubbles in living tissues and distortion of 420492_3825C3165387 cell membrane, influencing ion fluxes and intracellular activity. When ultrasound enters 420492_3825C3165387 body, it causes molecular friction and heats 420492_3825C3165387 tissues slightly. This effect is typically very minor as normal tissue perfusion dissipates most of 420492_3825C3165387 heat, but with high intensity, it can also cause small pockets of gas in body fluids or tissues to expand and contract/collapse in a phenomenon called cavitation; however this is not known to occur at diagnostic power levels used by modern diagnostic ultrasound units.[citation needed] In 2008, 420492_3825C3165387 AIUM published a 130-page report titled “American Institute of Ultrasound in Medicine Consensus Report on Potential Bioeffects of Diagnostic Ultrasound” stating that 420492_3825C3165387re are indeed some potential risks to administering ultrasound tests, which include “postnatal 420492_3825C3165387rmal effects, fetal 420492_3825C3165387rmal effects, postnatal mechanical effects, fetal mechanical effects, and bioeffects considerations for ultrasound contrast agents.” The long-term effects of tissue heating and cavitation have shown decreases in 420492_3825C3165387 size of red blood cells in cattle when exposed to intensities higher than diagnostic levels. However, long term effects due to ultrasound exposure at diagnostic intensity is still unknown. There are several studies that indicate harmful side effects on animal fetuses associated with 420492_3825C3165387 use of sonography on pregnant mammals. A Yale study in 2006 suggested exposure to ultrasound affects fetal brain development in mice. A typical fetal scan, including evaluation for fetal malformations, typically takes 10–30 minutes. The study showed that rodent brain cells failed to migrate to 420492_3825C3165387ir proper positions and remained scattered in incorrect parts of 420492_3825C3165387 brain. This misplacement of brain cells during 420492_3825C3165387ir development is linked to disorders ranging from “mental retardation and childhood epilepsy to developmental dyslexia, autism spectrum disorders and schizophrenia.” However, this effect was only detectable after 30 minutes of continuous scanning. No link has yet been made between 420492_3825C3165387 test results on animals such as mice and 420492_3825C3165387 possible effects on humans. Although 420492_3825C3165387 possibility exists that biological effects on humans may be identified in 420492_3825C3165387 future, currently most doctors feel that based on available information 420492_3825C3165387 benefits to patients outweigh 420492_3825C3165387 risks. The ALARA (As Low As Reasonably Achievable) principle has been advocated for an ultrasound examination — that is, keeping 420492_3825C3165387 scanning time and power settings as low as possible but consistent with diagnostic imaging — and that by that principle non-medical uses, which by definition are not necessary, are actively discouraged. Obstetric ultrasound can be used to identify many conditions that would be harmful to 420492_3825C3165387 mo420492_3825C3165387r and 420492_3825C3165387 baby. Many health care professionals consider 420492_3825C3165387 risk of leaving 420492_3825C3165387se conditions undiagnosed to be much greater than 420492_3825C3165387 very small risk, if any, associated with undergoing an ultrasound scan. According to Cochrane Review, routine ultrasound in early pregnancy (less than 24 weeks) appears to enable better gestational age assessment, earlier detection of multiple pregnancies and earlier detection of clinically unsuspected fetal malformation at a time when termination of pregnancy is possible. Sonography is used routinely in obstetric appointments during pregnancy, but 420492_3825C3165387 FDA discourages its use for non-medical purposes such as fetal keepsake videos and photos, even though it is 420492_3825C3165387 same technology used in hospitals. Obstetric ultrasound is primarily used to: Date 420492_3825C3165387 pregnancy (gestational age) Confirm fetal viability Determine location of fetus, intrauterine vs ectopic Check 420492_3825C3165387 location of 420492_3825C3165387 placenta in relation to 420492_3825C3165387 cervix Check for 420492_3825C3165387 number of fetuses (multiple pregnancy) Check for major physical abnormalities. Assess fetal growth (for evidence of intrauterine growth restriction (IUGR)) Check for fetal movement and heartbeat. Determine 420492_3825C3165387 sex of 420492_3825C3165387 baby Unfortunately, results are occasionally wrong, producing a false positive (420492_3825C3165387 Cochrane Collaboration is a relevant effort to improve 420492_3825C3165387 reliability of health care trials). False detection may result in patients being warned of birth defects when no such defect exists. Sex determination is only accurate after 12 weeks gestation. When balancing risk and reward, 420492_3825C3165387re are recommendations to avoid 420492_3825C3165387 use of routine ultrasound for low risk pregnancies. In many countries ultrasound is used routinely in 420492_3825C3165387 management of all pregnancies. According to 420492_3825C3165387 European Committee of Medical Ultrasound Safety (ECMUS) “Ultrasonic examinations should only be performed by competent personnel who are trained and updated in safety matters. Ultrasound produces heating, pressure changes and mechanical disturbances in tissue. Diagnostic levels of ultrasound can produce temperature rises that are hazardous to sensitive organs and 420492_3825C3165387 embryo/fetus. Biological effects of non-420492_3825C3165387rmal origin have been reported in animals but, to date, no such effects have been demonstrated in humans, except when a microbubble contrast agent is present.” None420492_3825C3165387less, care should be taken to use low power settings and avoid pulsed wave scanning of 420492_3825C3165387 fetal brain unless specifically indicated in high risk pregnancies. It should be noted that obstetrics is not 420492_3825C3165387 only use of ultrasound. Soft tissue imaging of many o420492_3825C3165387r parts of 420492_3825C3165387 body is conducted with ultrasound. O420492_3825C3165387r scans routinely conducted are cardiac, renal, liver and gallbladder (hepatic). O420492_3825C3165387r common applications include musculo-skeletal imaging of muscles, ligaments and tendons, ophthalmic ultrasound (eye) scans and superficial structures such as testicle, thyroid, salivary glands and lymph nodes. Because of 420492_3825C3165387 real time nature of ultrasound, it is often used to guide interventional procedures such as fine needle aspiration FNA or biopsy of masses for cytology or histology testing in 420492_3825C3165387 breast, thyroid, liver, kidney, lymph nodes, muscles and joints. Ultrasound scanners have different Doppler-techniques to visualize arteries and veins. The most common is colour doppler or power doppler, but also o420492_3825C3165387r techniques like b-flow are used to show bloodflow in an organ. By using pulsed wave doppler or continuous wave doppler bloodflow velocities can be calculated. Figures released for 420492_3825C3165387 period 2005–2006 by UK Government (Department of Health) show that non-obstetric ultrasound examinations constituted more than 65% of 420492_3825C3165387 total number of ultrasound scans conducted. Ultrasound is also increasingly being used in trauma and first aid cases, with emergency ultrasound becoming a staple of most EMT response teams. Fur420492_3825C3165387rmore, ultrasound is used in remote diagnosis cases where teleconsultation is required, such as scientific experiments in space or mobile sports team diagnosis. Non-invasive sensor Ultrasonic technology has 420492_3825C3165387 advantage of no direct contact between 420492_3825C3165387 contents of a vessel, tube or o420492_3825C3165387r materials. Various technologies exist including continuous wave and pulsed. For many processes in 420492_3825C3165387 medical, pharmaceutical, military and general industries this is an advantage over inline sensors that may contaminate 420492_3825C3165387 liquids inside a vessel or tube. The principle behind a Pulsed-Ultrasonic technology is that 420492_3825C3165387 transmit signal consists of short bursts of ultrasonic energy. After each burst, 420492_3825C3165387 electronics looks for a return signal within a small window of time corresponding to 420492_3825C3165387 time it takes for 420492_3825C3165387 energy to pass through 420492_3825C3165387 vessel. Only signal received during this window period will qualify for additional signal processing. The dry signal will not be received within this window, and 420492_3825C3165387refore will be ignored. Animal research ultrasonography Main article: Preclinical imaging Horses Diagnostic ultrasound is used externally in 420492_3825C3165387 equine for evaluation of soft tissue and tendon injuries, and internally in particular for reproductive work – evaluation of 420492_3825C3165387 reproductive tract of 420492_3825C3165387 mare and pregnancy detection. It may also be used in an external manner in stallions for evaluation of testicular condition and diameter as well as internally for reproductive evaluation (deferent duct etc.). Cattle Starting at 420492_3825C3165387 turn of 420492_3825C3165387 century, ultrasound technology began to be used by 420492_3825C3165387 beef cattle industry to improve animal health and 420492_3825C3165387 yield of cattle operations. Ultrasound is used to evaluate fat thickness, rib eye area, and intramuscular fat in living animals. It is also used to evaluate 420492_3825C3165387 health and characteristics of unborn calves. Ultrasound technology provides a means for cattle producers to obtain information that can be used to improve 420492_3825C3165387 breeding and husbandry of cattle. The technology can be expensive, and it requires a substantial time commitment for continuous data collection and operator training. Never420492_3825C3165387less, this technology has proven useful in managing and running a cattle breeding operation. Biomedical ultrasonic applications Ultrasound also has 420492_3825C3165387rapeutic applications, which can be highly beneficial when used with dosage precautions: According to RadiologyInfo, ultrasounds are useful in 420492_3825C3165387 detection of pelvic abnormalities and can involve techniques known as abdominal (transabdominal) ultrasound, vaginal (transvaginal or endovaginal) ultrasound in women, and also rectal (transrectal) ultrasound in men. Focused high-energy ultrasound pulses can be used to break calculi such as kidney stones and gallstones into fragments small enough to be passed from 420492_3825C3165387 body without undue difficulty, a process known as lithotripsy. Using 420492_3825C3165387rapeutic ultrasound to ablate tumors or o420492_3825C3165387r tissue non-invasively. This is accomplished using a technique known as High Intensity Focused Ultrasound (HIFU), also called focused ultrasound surgery (FUS). This procedure uses generally lower frequencies than medical diagnostic ultrasound (250–2000 kHz), but significantly higher time-averaged intensities. The treatment is often guided by Magnetic Resonance Imaging (MRI); 420492_3825C3165387 combination is 420492_3825C3165387n referred to as Magnetic resonance-guided focused ultrasound (MRgFUS). Delivering chemo420492_3825C3165387rapy to brain cancer cells and various drugs to o420492_3825C3165387r tissues is called acoustic targeted drug delivery (ATDD). These procedures generally use high frequency ultrasound (1–10 MHz) and a range of intensities (0–20 W/cm2). The acoustic energy is focused on 420492_3825C3165387 tissue of interest to agitate its matrix and make it more permeable for 420492_3825C3165387rapeutic drugs. Enhanced drug uptake using acoustic targeted drug delivery (ATDD). Using 420492_3825C3165387rapeutic ultrasound to generate cellular effects in soft tissue. This particular application has fallen out of favor as research has shown a lack of efficacy and a lack of scientific basis for proposed biophysical effects. Ultrasound has been used in cancer treatment. Cleaning teeth in dental hygiene. Focused ultrasound sources may be used for cataract treatment by phacoemulsification. Additional physiological effects of low-intensity ultrasound have recently been discovered, e.g. 420492_3825C3165387 ability to stimulate bone-growth and its potential to disrupt 420492_3825C3165387 blood-brain barrier for drug delivery. Ultrasound is essential to 420492_3825C3165387 procedures of ultrasound-guided sclero420492_3825C3165387rapy and endovenous laser treatment for 420492_3825C3165387 non-surgical treatment of varicose veins. Ultrasound-assisted lipectomy is lipectomy assisted by ultrasound. Liposuction can also be assisted by ultrasound. Doppler ultrasound is being tested for use in aiding tissue plasminogen activator treatment in stroke sufferers in 420492_3825C3165387 procedure called ultrasound-enhanced systemic thrombolysis. Low intensity pulsed ultrasound is used for 420492_3825C3165387rapeutic tooth and bone regeneration. Ultrasound can also be used for elastography. This can be useful in medical diagnoses, as elasticity can discern healthy from unhealthy tissue for specific organs/growths. In some cases unhealthy tissue may have a lower system Q, meaning that 420492_3825C3165387 system acts more like a large heavy spring as compared to higher values of system Q (healthy tissue) that respond to higher forcing frequencies. Ultrasonic elastography is different from conventional ultrasound, as a transceiver (pair) and a transmitter are used instead of only a transceiver. One transducer acts as both 420492_3825C3165387 transmitter and receiver to image 420492_3825C3165387 region of interest over time. The extra transmitter is a very low frequency transmitter, and perturbs 420492_3825C3165387 system so 420492_3825C3165387 unhealthy tissue oscillates at a low frequency and 420492_3825C3165387 healthy tissue does not. The transceiver, which operates at a high frequency (typically MHz) 420492_3825C3165387n measures 420492_3825C3165387 displacement of 420492_3825C3165387 unhealthy tissue (oscillating at a much lower frequency). The movement of 420492_3825C3165387 slowly oscillating tissue is used to determine 420492_3825C3165387 elasticity of 420492_3825C3165387 material, which can 420492_3825C3165387n be used to distinguish healthy tissue from 420492_3825C3165387 unhealthy tissue. Ultrasound has been shown to act synergistically with antibiotics in killing bacteria. Ultrasound has been postulated to allow thicker eukaryotic cell tissue cultures by promoting nutrient penetration. Ultrasound in 420492_3825C3165387 low MHz range in 420492_3825C3165387 form of standing waves is an emerging tool for contactless separation, concentration and manipulation of microparticles and biological cells, a method referred to as acoustophoresis. The basis is 420492_3825C3165387 acoustic radiation force, a non-linear effect which causes particles to be attracted to ei420492_3825C3165387r 420492_3825C3165387 nodes or anti-nodes of 420492_3825C3165387 standing wave depending on 420492_3825C3165387 acoustic contrast factor, which is a function of 420492_3825C3165387 sound velocities and densities of 420492_3825C3165387 particle and of 420492_3825C3165387 medium in which 420492_3825C3165387 particle is immersed. Ultrasound laboratory research based on clinically diagnostic systems is a popular way of making use of a real-time, lower cost (in comparison to MRI and CT) imaging modality for study of biomedical applications and image processing techniques. The ultrasound research interface is a tool that bridges 420492_3825C3165387 gap between useful laboratory equipment and a clinical device, and can be used to collect raw data for external or real-time analysis using special algorithms and protocols. Industrial ultrasound Non-destructive testing of a swing shaft showing spline cracking See also: Macrosonic and Ultrasonic testing Ultrasonic testing is a type of nondestructive testing commonly used to find flaws in materials and to measure 420492_3825C3165387 thickness of objects. Frequencies of 2 to 10 MHz are common but for special purposes o420492_3825C3165387r frequencies are used. Inspection may be manual or automated and is an essential part of modern manufacturing processes. Most metals can be inspected as well as plastics and aerospace composites. Lower frequency ultrasound (50–500 kHz) can also be used to inspect less dense materials such as wood, concrete and cement. Ultrasound can also be used for heat transfer in liquids. Researchers recently employed ultrasound in dry corn milling plant to enhance ethanol production. Ultrasonic manipulation and characterization of particles A researcher at 420492_3825C3165387 Industrial Materials Research Institute, Alessandro Malutta, devised an experiment that demonstrated 420492_3825C3165387 trapping action of ultrasonic standing waves on wood pulp fibers diluted in water and 420492_3825C3165387ir parallel orienting into 420492_3825C3165387 equidistant pressure planes. The time to orient 420492_3825C3165387 fibers in equidistant planes is measured with a laser and an electro-optical sensor. This could provide 420492_3825C3165387 paper industry a quick on-line fiber size measurement system. A somewhat different implementation was demonstrated at Pennsylvania State University using a microchip which generated a pair of perpendicular standing surface acoustic waves allowing to position particles equidistant to each o420492_3825C3165387r on a grid. This experiment, called “acoustic tweezers”, can be used for applications in material sciences, biology, physics, chemistry and nanotechnology. Ultrasonic cleaning Ultrasonic cleaners, sometimes mistakenly called supersonic cleaners, are used at frequencies from 20 to 40 kHz for jewellery, lenses and o420492_3825C3165387r optical parts, watches, dental instruments, surgical instruments, diving regulators and industrial parts. An ultrasonic cleaner works mostly by energy released from 420492_3825C3165387 collapse of millions of microscopic cavitations near 420492_3825C3165387 dirty surface. The bubbles made by cavitation collapse forming tiny jets directed at 420492_3825C3165387 surface. Ultrasonic disintegration Similar to ultrasonic cleaning, biological cells including bacteria can be disintegrated. High power ultrasound produces cavitation that facilitates particle disintegration or reactions. This has uses in biological science for analytical or chemical purposes (sonication and sonoporation) and in killing bacteria in sewage. High power ultrasound can disintegrate corn slurry and enhance liquefaction and saccharification for higher ethanol yield in dry corn milling plants. Ultrasonic humidifier The ultrasonic humidifier, one type of nebulizer (a device that creates a very fine spray), is a popular type of humidifier. It works by vibrating a metal plate at ultrasonic frequencies to nebulize (sometimes incorrectly called “atomize”) 420492_3825C3165387 water. Because 420492_3825C3165387 water is not heated for evaporation, it produces a cool mist. The ultrasonic pressure waves nebulize not only 420492_3825C3165387 water but also materials in 420492_3825C3165387 water including calcium, o420492_3825C3165387r minerals, viruses, fungi, bacteria, and o420492_3825C3165387r impurities. Illness caused by impurities that reside in a humidifier’s reservoir fall under 420492_3825C3165387 heading of “Humidifier Fever”. Ultrasonic humidifiers are frequently used in aeroponics, where 420492_3825C3165387y are generally referred to as foggers. Ultrasound Identification (USID) Ultrasound Identification (USID) is a Real Time Locating System (RTLS) or Indoor Positioning System (IPS) technology used to automatically track and identify 420492_3825C3165387 location of objects in real time using simple, inexpensive nodes (badges/tags) attached to or embedded in objects and devices, which 420492_3825C3165387n transmit an ultrasound signal to communicate 420492_3825C3165387ir location to microphone sensors. Ultrasonic welding In ultrasonic welding of plastics, high frequency (15 kHz to 40 kHz ) low amplitude vibration is used to create heat by way of friction between 420492_3825C3165387 materials to be joined. The interface of 420492_3825C3165387 two parts is specially designed to concentrate 420492_3825C3165387 energy for 420492_3825C3165387 maximum weld strength. Ultrasound and animals Bats use ultrasounds to navigate in 420492_3825C3165387 darkness. Electronic pest control Main article: Electronic pest control Bats Bats use a variety of ultrasonic ranging (echolocation) techniques to detect 420492_3825C3165387ir prey. They can detect frequencies beyond 100 kHz, possibly up to 200 kHz. Insects Many insects have good ultrasonic hearing and most of 420492_3825C3165387se are nocturnal insects listening for echolocating bats. This includes many groups of moths, beetles, praying mantids and lacewings. Upon hearing a bat 420492_3825C3165387 insects will make evasive manoeuvres to escape being caught by 420492_3825C3165387 bat. Ultrasonic frequencies trigger a reflex action in 420492_3825C3165387 noctuid moth that cause it to drop a few inches in its flight to evade attack. Tiger moths also emit clicks which may disturb bats’ echolocation, but may also in o420492_3825C3165387r cases evade being eaten by advertising 420492_3825C3165387 fact that 420492_3825C3165387y are poisonous by emitting sound. Ultrasound generator/speaker systems are sold with claims that 420492_3825C3165387y frighten away rodents and insects, but 420492_3825C3165387re is no scientific evidence that 420492_3825C3165387 devices work. Dogs Dogs can hear sound at higher frequencies than humans can. A dog whistle exploits this by emitting a high frequency sound to call to a dog. Many dog whistles emit sound in 420492_3825C3165387 upper audible range of humans, but some, such as 420492_3825C3165387 silent whistle, emit ultrasound at a frequency in 420492_3825C3165387 range 18–22 kHz. Dolphins and whales It is well known that too420492_3825C3165387d whales (Odontocetes), including dolphins can hear ultrasound and use ultrasonic sounds in 420492_3825C3165387ir navigational system (biosonar) to orient and capture prey. Porpoises have 420492_3825C3165387 highest known upper hearing limit, at around 160 kHz. In 2011 researchers in 420492_3825C3165387 United States and Great Britain, using a CymaScope, an instrument which produces visible patterns from sound, found that part of dolphin communication consists of receiving and transmitting sound pictures. It is almost certain that to some extent this ability is shared by 420492_3825C3165387 entire dolphin family. Fish Several types of fish can detect ultrasound. In 420492_3825C3165387 order Clupeiformes, members of 420492_3825C3165387 subfamily Alosinae (shad), have been shown to be able to detect sounds up to 180 kHz, while 420492_3825C3165387 o420492_3825C3165387r subfamilies (e.g. herrings) can hear only up to 4 kHz. Sonochemistry Main article: Sonochemistry Power ultrasound in 420492_3825C3165387 20–100 kHz range is used in chemistry. The ultrasound does not interact directly with molecules to induce 420492_3825C3165387 chemical change, as its typical wavelength (in 420492_3825C3165387 millimeter range) is too long compared to 420492_3825C3165387 molecules. Instead: It causes cavitation which causes local extremes of temperature and pressure in 420492_3825C3165387 liquid where 420492_3825C3165387 reaction happens. It breaks up solids and removes passivating layers of inert material to give a larger surface area for 420492_3825C3165387 reaction to occur over. Both of 420492_3825C3165387se make 420492_3825C3165387 reaction faster. In 2008, Atul Kumar reported syn420492_3825C3165387sis of Hantzsch esters and polyhydroquinoline derivatives via multi-component reaction protocol in aqueous micelles using ultrasound. It is used in extraction, using different frequencies. Ultrasonic range finding Principle of an active sonar Main article: sonar A common use of ultrasound is in range finding; this use is also called SONAR, (sound navigation and ranging). This works similarly to RADAR (radio detection and ranging): An ultrasonic pulse is generated in a particular direction. If 420492_3825C3165387re is an object in 420492_3825C3165387 path of this pulse, part or all of 420492_3825C3165387 pulse will be reflected back to 420492_3825C3165387 transmitter as an echo and can be detected through 420492_3825C3165387 receiver path. By measuring 420492_3825C3165387 difference in time between 420492_3825C3165387 pulse being transmitted and 420492_3825C3165387 echo being received, it is possible to determine how far away 420492_3825C3165387 object is. The measured travel time of SONAR pulses in water is strongly dependent on 420492_3825C3165387 temperature and 420492_3825C3165387 salinity of 420492_3825C3165387 water. Ultrasonic ranging is also applied for measurement in air and for short distances. Such method is capable for easily and rapidly measuring 420492_3825C3165387 layout of rooms. Although range finding underwater is performed at both sub-audible and audible frequencies for great distances (1 to several kilometers), ultrasonic range finding is used when distances are shorter and 420492_3825C3165387 accuracy of 420492_3825C3165387 distance measurement is desired to be finer. Ultrasonic measurements may be limited through barrier layers with large salinity, temperature or vortex differentials. Ranging in water varies from about hundreds to thousands of meters, but can be performed with centimeters to meters accuracy As a weapon See Sonic weaponry. O420492_3825C3165387r uses Ultrasound when applied in specific configurations can produce short bursts of light in an exotic phenomenon known as sonoluminescence. This phenomenon is being investigated partly because of 420492_3825C3165387 possibility of bubble fusion (a nuclear fusion reaction hypo420492_3825C3165387sized to occur during sonoluminescence). Researchers have successfully used ultrasound to regenerate dental material. Ultrasound is used when characterizing particulates through 420492_3825C3165387 technique of ultrasound attenuation spectroscopy or by observing electroacoustic phenomena. In rheology, an acoustic rheometer relies on 420492_3825C3165387 principle of ultrasound. In fluid mechanics, fluid flow can be measured using an ultrasound flow meter. High and ultra high ultrasound waves are used in Acoustic microscopy Audio can be propagated by modulated ultrasound. Ultrasonic testing has been used to inspect 420492_3825C3165387 quality of welded metal joints for many years.