Device to Overcome Sense of Sight and Hear

SENSE OF SIGHT. The kernels ar sensory organs. They cargo deck the brain updated with information closely is what happening around the body. Both contain millions of footling sensors that send messages along nerves to the brain. Sensors in the centres respond to light and, through the brain, let us see the world. Sensors in the skin respond to billet and al wiped out(p)s us to feel. * * * * The seeing eye Light enters the eye through the clear cornea. It then passes through the pupil and is contracted by the lense on the retina. This load layer covers the back of the eye and contains cells that ar sensitive to light.When light hits the cells, they send signals to the brain. There, the signals argon bingeed into pictures so we house see. Telescope Atelescopeis an putz that aids in the observation of remote objects by collecting electromagnetic radiation(such asvisible light). The initial known practical telescopes were invented in theNetherlandsat the beginning of the 17th one C, employ methamphetamine hydrochloride lenses. They found intent in terrestrial applications and astronomy. Within a few decades, thereflecting telescopewas invented, which utilize mirrors.In the 20th century manhoody new types of telescopes were invented, includingradio telescopesin the 1930s andinfrared telescopesin the 1960s. The wordtelescopenow refers to a wide range of performers key outing disparate regions of theelectromagnetic spectrum, and in some cases early(a) types of detectors. History The earliest recorded working telescopes were therefracting telescopesthat seemed in the Netherlandsin 1608. Their nurture is credited to three individualsHans Lippersheyand Zacharias Janssen, who were spectacle makers in Middelburg, andJacob Metiusof Alkmaar. 4Galileohear about the Dutch telescope in June 1609, reinforced his own within a month,5and greatly improved upon the heading in the following year. The idea that the im individualal, or light-gathering eleme nt, could be a mirror instead of a lens was being investigated soon after the invention of the refracting telescope. 6The potential advantages of usingparabolic mirrorsreduction of worldwide aberrationand nochromatic aberrationled to many proposed public figures and several attempts to buildreflecting telescopes. 7In 1668,Isaac Newtonbuilt the first practical reflecting telescope, of a mark which now bears his name, theNewtonian reflector. The invention of theachromatic lensin 1733 partially corrected color aberrations present in the simple lens and enabled the construction of shorter, more than kick the bucketal refracting telescopes. Reflecting telescopes, though non arrangeed by the color problems seen in refractors, were hampered by the use of fast tarnishingspeculum metalmirrors employed during the 18th and early nineteenth centurya problem alleviated by the introduction of silver coated glass mirrors in 1857,8and aluminized mirrors in 1932. 9The maximum physical size lim it for refracting telescopes is about 1 meter (40inches), dictating that the vast majority of large optical investigateing telescopes built since the tress of the 20th century have been reflectors. The largest reflecting telescopes currently have objectives bigger than 10m (33feet). The 20th century also saw the development of telescopes that worked in a wide range of wavelengths fromradiotogamma-rays. The first purpose built radio telescope went into operation in 1937. Since then, a tremendous variety of complex astronomical instruments have been developed.How to use * Find an area where the items you wish to celestial horizon arent obstructed by trees to set up your telescope so that you get a clear fit of the sky. * Look to see if your telescope has a north-polar axis of rotation. If it does, it will track whatever you are looking at. If you have a telescope with a polar axis, follow your manufacturers directions on how to align the polar axis and the finder scope. * Select the ocular with the lowest magnification that you have. Always start with the lowest magnification eye member until you become more experienced in using your telescope. Locate the item in the night sky that you wish to observe and focus in on it. Move the planet or star you are viewing as close to the contract of the field of view in the eyepiece as possible. * Re ingrain the low magnification eyepiece and re vex it with an eyepiece with a loftyer magnification. * Readjust the alignment of the telescope when the planet or star drifts out of view if you have a manual telescope mount. * broaden in this manner, observing different visible planets and stars. Binoculars Binoculars,field glassesorbinocular telescopesare a pair of identical or mirror-symmetricaltelescopesmount side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. Most are sized to be held using both hands, although sizes vary widely fromopera glassesto large pedestal mounted military models. Many different abbreviations are apply for binoculars, includingglasses, nocs ,noculars ,binosandbins. strange a (monocular) telescope, binoculars give users a three-dimensional ikon for nearer objects the two views, presented to ach of the viewers eyes from slightly different viewpoints, produce a merged view with animpression of depth. History No sooner was the telescope invented in than the early 1600s than did astronomers get the idea of mounting two of them together, effectively inventing the first binoculars. Galileo (who is often wrongly credited with having invented binoculars) adapted an earlier design, using optics that combined convex and concave lenses to create a magnifying effect just like that utilize today in the cheapest nonprismatic glasses marketed for sports or theater viewing, or for use by children.In the mid-1850s, Ignazio Porro of Italy patented a design using two prisms constructe d in a Z rule to present the viewer with an image that non only is better magnified, but has depth. The Porro prism design was followed a few decades later by the roof prism, in which the prisms are constructed in one unit. Soon, binoculars were adapted for military use, and were employed during the Civil War. Quality made a big jump around the turn of the 19th century, and continued to be refined in the early 1900s. With the advent of World War II, more manufacturers entered the binoculars market, including, in the United States, Bausch Lomb.Germany continued with its merchandise of highly regarded binoculars, with a few changes. For example, Zeiss, one of the top names in binoculars, experienced a confusing shift, with a new factory established in East Germany nether Russian control with the Zeiss name while another factory named Zeiss was began exporting from West Germany, according to a history in the 1961 agree Binoculars and Scopes and Their exercisings in Photography, by Robert J. and Elsa Reichert. Japan exports binoculars via mingled manufacturers, and some U. S. ompanies import Japanese-made binoculars but sell them under the U. S. company name. How to use * tramp the binocular strap around your neck. Wearing the neck-strap gives you the ability to use both hands while you are using the binoculars. * Adjust the barrels of the binoculars each(prenominal) side you look into to the width of your face. Generally, all you need to do is move the barrels closer together or further apart as you clench the binoculars up to your eyes. If you have adjusted the binoculars correctly, you should not see a black border when you look through the eyepieces. Locate the central focus wheel, usually in the centre of the two barrels of the binoculars. Turn the wheel slowly as you look at a particular object in the distance to get the best focus for your eyes. * Fine-tune your viewing even more if you have a diopter focus mechanism on your binoculars. non all binoculars have this focus element, which helps compensate for the difference in vision that you might experience in each of your eyes. The diopter focus qualifying wheel is usually on the right-hand barrel. * Keep both eyes open as you view your target objects.You might need to re-focus from time to time. * peel your binoculars after using them. A soft, damp cloth is sufficient for the body of the binoculars. Treated tissue paper employ to clean cameras and eye glasses is safe for wiping the lenses. Store binoculars in their carrying case when youre not using them. Microscope Amicroscope(from theAncient Greek ,mikros, small and ,skopein, to look or see) is aninstrumentused to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is calledmicroscopy .Microscopicmeans unseeable to the eye unless aided by a microscope. There are many types of microscopes, the most common and first to be invented is theoptical micros copewhich useslightto image the sample. Other major types of microscopes are theelectron microscope(both thetransmission electron microscopeand thescanning electron microscope) and the various types ofscanning probe microscope History The first microscope to be developed was the optical microscope, although the original spotter is not easy to learn. An early microscope was made in 1590 inMiddelburg, Netherlands. 1 devileyeglassmakers are variously given creditHans Lippershey (who developed an earlytelescope) andZacharias Janssen. Giovanni Fabercoined the namemicroscope forGalileo Galileis escalate microscope in 16252(Galileo had called it the occhiolino or critical eye). How to use. * When moving your microscope, always carry it with both hands (Figure 1, below). Grasp the arm with one hand and place the other hand under the base for support. * Turn the revolving nosepiece so that the lowest power objective lens is clicked into position (This is also the shortest objective lens ). Your microscope veer should be prepared with a coverslip or cover glass over the specimen. This will help protect the objective lenses if they touch the slide. Place the microscope slide on the stage and fasten it with the stage clips. You can push down on the back end of the stage clip to open it. * Look at the objective lens and the stage from the side (Figure 2) and turn the coarse focus knob so that the objective lens moves downward (or the stage, if it moves, goes upward). Move it as far as it will gowithout touching the slide * 5.Now, look through the eyepiece and adjust the illuminator (or mirror) and diaphragm (Figure 3) for the greatest amount of light. * Slowly turn the coarse fitting so that the objective lens goesup(away from the slide). Continue until the image comes into focus. Use the fine adjustment, if available, for fine focusing. If you have a microscope with a moving stage, then turn the coarse knob so the stage moves downward or away from the objective l ens. * Move the microscope slide around so that the image is in the center of the field of view and readjust the mirror, illuminator or diaphragm for the clearest image. Now, you should be able to change to the next objective lenses with only minimal use of the focusing adjustment. Use the fine adjustment, if available. If you cannot focus on your specimen, repeat steps 4 through 7 with the higher power objective lens in place. Do not allow the objective lens to touch the slide * The proper way to use a monocular microscope is to look through the eyepiece with one eye and keep the other eye open (this helps avoid eye strain). If you have to close one eye when looking into the microscope, its ok. Remember, e verything is upside down and backwards.When you move the slide to the right, the image goes to the left * Do not touch the glass part of the lenses with your fingers. Use only special lens paper to clean the lenses. * When finished, raise the cannular structure (or degrade the stage), click the low power lens into position and remove the slide. * Always keep your microscope covered when not in use. Submarine Asubmarineis awatercraftcapable of independent operation underwater. It differs from asubmersible, which has more limited underwater capability. The terminus submarine most commonly refers to a large crewed self-reliant vessel.However, historically or colloquially, submarine can also refer to medium-sized or smaller vessels (midget submarines,wet subs),remotely operated vehiclesorrobots. The adjectivesubmarine, in terms such assubmarine cable, means under the sea. The nounsubmarineevolved as a shortened form ofsubmarine boat(and is often further shortened tosub). 1For reasons ofnaval traditionsubmarines are usually referred to as boats rather than as ships, regardless of their size. Although experimental submarines had been built before, submarine design took off during the 19th century, and they were adopted by several navies.Submarines were first widely used duringWorld War I(19141918) and now figure in many largenavies. Military usage includes attacking enemy coat ships or submarines,aircraft carrierprotection,blockaderunning,ballistic missile submarinesas part of a nuclear strike force,reconnaissance, conventional land attack (for example using acruise missile), and cover charge insertion ofspecial forces. Civilian uses for submarines includemarine science, salvage, exploration and facility inspection/maintenance. Submarines can also be modified to perform more change functions such as search-and-rescue missions orundersea cablerepair.Submarines are also used in tourism, and forundersea archaeology. Most large submarines consist of a cylindric body with hemispherical (and/or conical) ends and a vertical organize, usually located amidships, which houses communications and sensing devices as hearty as periscopes. In modern submarines this structure is the sail in American usage, and fin in European usage. A conning tow er was a feature of earlier designs a separate pressure hull above the main body of the boat that allowed the use of shorter periscopes.There is a propeller (or pump jet) at the rear and various hydrodynamic control fins as well as ballast tanks. Smaller, deep nose dive and specialty submarines whitet car horn deviate significantly from this traditional layout. Submarines have one of the largest ranges of capabilities in any vessel, ranging from small self-governing examples to one- or two-person vessels operating for a few hours, to vessels which can remain submerged for 6 months such as theRussianTyphoon class the biggest submarines ever built and in use. Submarines can work at greater depths than are survivable or practical for humandivers.Modern deep diving submarines are derived from thebathyscaphe, which in turn was an evolution of thediving bell. History The first submersible of which we have reliable information on its construction was built in 1620 byCornelius Drebbel, a Dutchmanin the service of mob I of England. It was created to the tireds of the design outseamed by English mathematicianWilliam Bourne. It was propelled by means of oars. The precise nature of the submarine type is a matter of some lean some claim that it was merely a bell towed by a boat. Two improved types were tested in theThames among 1620 and 1624.In 2002 a two-person version of Bournes design was built for theBBCTV programmeBuilding the ImpossiblebyMark Edwards, and successfully rowed under water atDorney Lake,Eton. Though the first submersible vehicles were tools for exploring under water, it did not take long for journeymans to recognize their military potential. The strategic advantages of submarines were set out by BishopJohn WilkinsofChester, England, inMathematicall Magickin 1648 1. This private a man whitethorn thus go to any coast in the world invisibly, without discovery or prevented in his journey. 2.This safe, from the uncertainty of Tides, and the violence of T empests, which do never move the sea above five or six paces deep. From Pirates and Robbers which do so infest other voyages from ice and great frost, which do so much exhibit the passages towards the Poles. 3. It may be of great advantages against a Navy of enemies, who by this may be undermined in the water and blown up. 4. It may be of special use for the relief of any place besieged by water, to convey unto them invisible supplies and so likewise for the surprisal of any place that is accessible by water. 5.It may be of unspeakable benefit for submarine experiment How it work The adaptations and inventions that allow sailors to not only fight a battle, but also live for months or even years underwater are some of the most brilliant developments in military history. In this article, you will see how a submarine dives and surfaces in the water, how life support is maintained, how the submarine gets its power, how a submarine finds its way in the deep ocean and how submarines mig ht be rescued. ultra healthful scanning device Ultra nearis a cyclic rightpressure wave with afrequencygreater than the upper limit of the humanhearing range.Ultrasound is thus not obscure from normal (audible) sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is approximately 20 kHz(20,000 hertz) in healthy, young adults. Ultrasound devices operate with frequencies from 20kHz up to several gigahertz. Ultrasound is used in many different fields. Ultrasonic devices are used to detect objects and measure distances. Ultrasonic imaging (sonography) is used in human and veterinary medicine. In non-destructive testing of products and structures, ultrasonography is used to detect invisible flaws.Industrially, ultrasound is used for cleaning and for mixing, and to accelerate chemical processes. Organisms such as bats and porpoises use ultrasound for locating prey and obstacles. Ultrasonicsis t he application ofultrasound. Ultrasound can be used for imaging, detection, measurement, and cleaning. At higher power levels ultrasonics are useful for changing the chemical. History Acoustics, the science of sound, starts as far back asPythagorasin the 6th century BC, who wrote on the mathematical properties of stringed instruments. SirFrancis Galtonconstructeda whistleproducing ultrasound in 1893.The first technological application of ultrasound was an attempt to detect icebergs byPaul Langevinin 1917. Thepiezoelectric effectdiscovered by Jacques and Pierre Curie in 1880 was useful in transducers to generate and detect ultrasonic waves in air and water. 2Echolocationin bats was discovered byLazzaro Spallanzaniin 1794, when he demonstrated that bats hunted and navigated by inaudible sound and not vision. How it works There are many reasons to get an ultrasound. Perhaps youre pregnant, and your obstetrician wants you to have an ultrasound to check on the developing baby or delay the due date.Maybe youre having problems with bloodcirculation in a limb or your heart, and your doctor has requested a Doppler ultrasound to look at the blood flow. Ultrasound has been a popular medical imaging technique for many years. Ultrasoundorultrasonography is a medical imaging technique that uses high frequency sound waves and their echoes. The technique is similar to the echolocation used by bats, whales and dolphins, as well as SONAR used bysubmarines. In this article, well look at how ultrasound works, what type of ultrasound techniques are vailable and what each technique can be used for. Magnifying glass Amagnifying glass(called ahand lensin laboratory contexts) is aconvex lensthat is used to produce amagnifiedimageof an object. Thelensis usually mounted in a grade with a handle (see image). Asheet magnifierconsists of many very narrow concentric ring-shaped lenses, such that the combination acts as a single lens but is much thinner. This arrangement is known as aFre snel lens. The magnifying glass is an icon ofdetective fiction, particularly that ofSherlock Holmes. History The earliest evidence of a magnifying device, a convex lens forming a magnified image was Aristophaness lens, from 424 BC, a glass globe filled with water. (Senecawrote that it could be used to read letters no matter how small or dim). 1Roger Bacondescribed the properties of a magnifying glass in 13th-centuryEngland. Eyeglasseswere developed in 13th-centuryItaly. How it works Themagnificationof a magnifying glass depends upon where it is placed between the users eye and the object being viewed, and the total distance between them.Themagnifying poweris equivalent toangular magnification(this should not be at sea withoptical power, which is a different quantity). The magnifying power is the ratio of the sizes of the images formed on the users retina with and without the lens. 3For the without case, it is typically assumed that the user would bring the object as close to the ey e as possible without it becoming blurry. This point, known as thenear point,varies with age. In a young child it can be as close as 5cm, while in an elderly person it may be as far as one or two metres.Magnifiers are typically characterized using a standard value of 0. 25m. The highest magnifying power is obtained by putting the lens very close to the eye and moving the eye and the lens together to obtain the bestfocus. The object will then typically also be close to the lens. Sense of hearing Hearing,auditory perception, orearshotis the ability to perceivesoundby detectingvibrations,changes in the pressure of the surrounding medium through time, through an organ such as theear. Sound may be heard throughsolid,liquid, orgaseousmatter. It is one of the traditional fivesenses.The inability to hear is calleddeafness. In humans and other vertebrates, hearing is performed in the beginning by theauditory system vibrations are detected by theearand transduced into nerve impulses that are perceived by thebrain(primarily in thetemporal lobe). the likes oftouch, audition requires esthesia to the movement of molecules in the world outside the organism. Both hearing and touch are types of mechanosensation. Stethoscope Thestethoscopeis an acousticmedicaldevice forauscultation, or perceive to the internal sounds of an animal or human body.It is often used to listen to lung andheart sounds. It is also used to listen tointestinesand blood flow inarteriesandveins. In combination with asphygmomanometer, it is commonly used for measurements ofblood pressure. Less commonly, mechanics stethoscopes are used to listen to internal sounds made by machines, such as diagnosing a malfunctioning automobile engine by listening to the sounds of its internal parts. Stethoscopes can also be used to check scientific vacuum chambers for leaks, and for various other small-scale acoustic monitoring tasks.A stethoscope that intensifies auscultatory sounds is calledphonendoscope. History The s tethoscope was invented inFrancein 1816 byRene Laennecat theNecker-Enfants Malades HospitalinParis. 1It consisted of a wooden tube and was monaural. His device was similar to the commonear trumpet, a historical form of hearing aid indeed, his invention was almost indistinguishable in structure and function from the trumpet, which was commonly called a microphone. The first flexible stethoscope of any sort may have been a binaural instrument with articulated joints not very clearly described in 1829. 2In 1840,Golding Birddescribed a stethoscope he had been using with a flexible tube. Bird was the first to publish a description of such a stethoscope but he noted in his paper the prior existence of an earlier design (which he thought was of little utility) which he described as the snake ear trumpet. Birds stethoscope had a single earpiece. 3In 1851, Irish physician Arthur Leared invented a binaural stethoscope, and in 1852 George Cammann perfected the design of the instrument for comm ercial production, which has become the standard ever since.Cammann also wrote a major treatise on diagnosis by auscultation, which the refined binaural stethoscope made possible. By 1873, there were descriptions of a differential stethoscope that could connect to slightly different locations to create a slight stereo effect, though this did not become a standard tool in clinical practice. The medical historianJacalyn Duffinhas argued that the invention of the stethoscope marked a major step in the redefinition of disease from being a plenty of symptoms, to the current sense of a disease as a problem with an anatomical system even if there are no noticeable symptoms.This re-conceptualiization occurred in part, Duffin argues, because prior to the stethoscopes, there were no non-lethal instruments for exploring internal anatomy. 4 Rappaport and Sprague designed a new stethoscope in the 1940s, which became the standard by which other stethoscopes are measured, consisting of two sides, one of which is used for the respiratory system, the other for the cardiovascular system. The Rappaport-Sprague was later made byHewlett-Packard. HPs medical products division was spun off as part of Agilent Technologies, Inc. , where it became Agilent Healthcare.Agilent Healthcare was purchased byPhilipswhich became Philips Medical Systems, before the walnut-boxed, $300, original Rappaport-Sprague stethoscope was finally abandoned ca. 2004, along with Philips brand (manufactured by Andromed, of Montreal, Canada) electronic stethoscope model. The Rappaport-Sprague model stethoscope was heavy and short (1824in (4661cm)) with an antiquated appearance recognisable by their two large independent latex rubber tubes connecting an exposed-leaf-spring-joined-pair of opposing f-shaped chrome-plated brass binaural ear tubes with a dual-head actors assistant piece.How to use * moderately off the earpieces before placing the stethoscope into your ears, especially if others share it or you se ldom use it. In the hospital, earpieces are wiped with alcohol prep swabs. * asseverate the chest piece between your palms to warm it before placing it on a persons chest. Thirty seconds is usually long enough to remove the chill. * Place the stethoscope into your ears. * Hold the chest piece in your hand. With the other hand, tap a finger against the chest piece and listen. Many stethoscopes have reversible heads, which can be incompletely swiveled and block sound. Grip the chest piece between your middle and index fingers to provide firm contact with the skin. * To minimize extraneous noises, avoid touching or rubbing the tubing or chest piece against clothing, bedcovers or hair. * Place the chest piece onto the part of the body you want to listen to. For the heart, this is a few inches above the left nipple. You should hear a steady lub dub. This is known as the apical pulse. * Store your stethoscope so that the tubing isnt kinked when you put it away. In hospitals, when stetho scopes are not being used, theyre generally hung by their earpieces so that the tubing can dangle freely.Loudhailer Amegaphone, verbalize-trumpet,bullhorn,blowhorn, orloud haileris a portable, usually hand-held, cone-shapedacoustic hornused toamplifya persons voice or othersoundsand direct it in a given direction. The sound is introduced into the narrow end of the megaphone, by holding it up to the face and speaking into it, and the sound waves radiate out the wide end. The megaphone increases the volume of sound by increasing theacoustic impedanceseen by thevocal music cords,matchingthe impedance of the vocal cords to the air, so that more sound power is radiated.It also serves to direct the sound waves in the direction the horn is pointing. It somewhat distorts the sound of the voice because thefrequency reparteeof the megaphone is greater at higher soundfrequencies. Since the 1970s the voice-poweredacoustic megaphonedescribed above has been replaced by theelectric megaphone, whi ch uses electric power toamplifythe voice. History The initial inventor of the speaking trumpet is a subject of historical controversy, as bothSamuel MorlandandAthanasius Kircherlay claim to the device.Morland, in a work published in 1655, wrote about his experimentation with different horns and his most successful variant. This loudest horn was made of over 20 feet of copper and could supposedly project vocalizations as far as a mile and a half. 1 Twenty years earlier, Kircher described a device that could be used for both broadcasting on one end and overhearing on the other. His coiled horn would be wedged into the side of a building, connecting a speaker or listener inside with the surrounding environment.Morland favored a straight, tube-shaped speaking device, where an initial sound would reverberate in waves through the instrument and gradually become louder. Kirchers horn, on the other hand, utilized a cochleate design, where the horn was twisted and coiled, unlike Morlands de sign. A later,papier-machetrumpet of special design was the Sengerphone. 2 The term megaphone was first associated withThomas Edisons instrument 200 years later. In 1878, Edison developed a device similar to the speaking trumpet in hopes of benefiting the deaf and hard of hearing.His variation included three separate funnels lined up in a row. The two outer funnels, which were six feet and eight inches long, were made of paper and connected to a tube inserted in each ear. The middle funnel was similar to Morlands speaking trumpet, but had a larger slot to insert a users mouth. 3 With Edisons megaphone, a low whisper could be heard a thousand feet away, while a normal tone of voice could be heard roughly two miles away. On the listening end, the receiver could hear a low whisper at a thousand feet away. However the apparatus was much too large to be portable, limiting its use.George Prescott wrote The principal drawback at present is the large size of the apparatus. Since the 1960s acoustic megaphones have generally been replaced by electric versions(below), although the cheap, light, rugged acoustic megaphone is mute used in a few venues, like cheering at sporting events,cheerleading, and bylifeguardsat pools and beaches where the moisture could damage the electronics of electric megaphones. How to use * Hold the megaphone several inches from your mouth with the small end toward you and the large end away from you. * Point the large end of the megaphone toward the crowd you wish to exhort. Speak loudly or shout into the small end. * Wait for the crowds response, then repeat Step 3 as necessary. Sonar Sonar(originally anacronymforSoundNavigationAndRanging) is a technique that usessoundpropagation (usually underwater, as insubmarine navigation) tonavigate, communicate with or detect objects on or under the surface of the water, such as other vessels. Two types of technology share the name sonarpassivesonar is essentially listening for the sound made by vessels activesonar is emitting pulses of sounds and listening for echoes.Sonar may be used as a means ofacoustic locationand of measurement of the echo characteristics of targets in the water. Acoustic location in air was used before the introduction ofradar. Sonar may also be used in air for robot navigation, andSODAR(an upward looking in-air sonar) is used for atmospheric investigations. The termsonaris also used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from very low (infrasonic) to extremely high (ultrasonic). The study of underwater sound is known asunderwater acousticsorhydroacoustics.History Although some animals (dolphins and bats) have used sound for communication and object detection for millions of years, use by humans in the water is initially recorded byLeonardo Da Vinciin 1490 a tube inserted into the water was said to be used to detect vessels by placing an ear to the tube. 1 In the 19th century an underwate r bell was used as an ancillary tolighthousesto provide warning of hazards. The use of sound to echo locate underwater in the same way asbatsuse sound for aerial navigation seems to have been prompted by theTitanic incident of 1912.The worlds firstpatentfor an underwater echo ranging device was filed at the BritishPatent Officeby English meteorologistLewis Richardsona month after the sink of the Titanic,2and a German physicistAlexander Behmobtained a patent for an echo sounder in 1913. The Canadian engineerReginald Fessenden, while working for the Submarine Signal guild in Boston, built an experimental system beginning in 1912, a system later tested in Boston Harbor, and finally in 1914 from the U. S. revenue (now Coast Guard) Cutter Miami on theGrand BanksoffNewfoundlandCanada. 23In that test, Fessenden demonstrated depth sounding, underwater communications (Morse Code) and echo ranging (detecting an iceberg at two miles (3km) range). 45The so-calledFessendenoscillator, at ca. 500Hz frequency, was unable to determine the bearing of the berg due to the 3 metre wavelength and the small dimension of the transducers radiating face (less than 1 metre in diameter). The tenMontreal-builtBritish H class submarineslaunched in 1915 were equipped with aFessenden oscillator. 6 DuringWorld War Ithe need to detectsubmarinesprompted more research into the use of sound.The British made early use of underwater hydrophones, while the French physicistPaul Langevin, working with a Russian immigrant electrical engineer,Constantin Chilowski, worked on the development of active sound devices for detecting submarines in 1915 using quartz. Althoughpiezoelectricand magnetostrictive transducers later superseded theelectrostatictransducers they used, this work influenced future designs. Lightweight sound-sensitive plastic film and fibre optics have been used forhydrophones(acousto-electric transducers for in-water use), whileTerfenol-Dand PMN (lead magnesium niobate) have been devel oped for projectors.How to use * Install the transmitter. Youll usually have a choice between mounting the transmitter beneath the boat, to a trolling motor or atop the interior hull and letting it drop into the water. * Set the seek finding sonars sensitivity while watching the display. When the sensitivity is too high, there will be static-like patterns on the display. If the sensitivity is too low, not even the bottom of the body of the water will appear on screen. * 3 * Determine the depth of the body of water. This will be a numeric value on the fish finder sonar systems display.This is important in helping you to determine how much fishing line to feed out from your pole. * Get accustomed to the displays representation of the body of water. The bottom will appear as a jagged, solid line near the bottom of your display. The surface of the water appears as a jumbled static-filled horizontal line at the top of your fish finder sonar systems display. * Learn to identify patterns on your display that are brush piles if youre fishing on a lake. Brush piles appear as blobs resting on the lake bottom.Fish such as bass hide out in brush piles, so consider fishing near these echoes. * Learn how to identify fish on your fish finder sonar system display with the fish symbols turned off. With the symbols turned off, fish appear as short trend lines above the bottom of the body of water. Adjust the fish finder sonars noise filter if there are lines in your display that look like haphazard static. * Remember what the fish finder sonar display was indicating when you catch a fish. This will help you to learn how to use your system to catch more fish later if you keep in mind what to look for.